Sunday, November 23, 2014

Power Plug Energy Meter - Now wireless!

This is the second post about my work on the cheap China-style energy meter hack.
My last post covered how I with a logic analyzer successfully (but not in the safest way) sniffed the SPI-transmission on the device and managed to decipher the data. And then how I used an Arduino Nano to do the sniffing for me with an interrupt driven approach. The Arduino  translated the bits and bytes to power and voltage values that it continuously printed on the PC's Serial monitor via an USB-cable.

The next obvious step in this project is to get the energy meter to transmit the data wirelessly. Not only would this mean that I could grab data from several energy meters simultaneously, but it also creates a safe way of debugging the device since my previous setup (which I abandoned after reading some of the comments on Hackaday.com) meant connecting the mains neutral to the computers ground (do not try this at home!!!)

Today's post will cover how I managed to get an Arduino pro mini (3.3V) to sniff the energy meters SPI and transmit the data wirelessly with a nRF24L01+ to an Arduino Nano connected to a computer. The neat thing with this setup is that the Arduino pro mini and the nRF fits perfectly within the casing of the energy meter, and are both driven by the internal power that charges the rechargeable battery that you'll find in the meter.


The total cost of components for each energy meter is:
Energy meter             £7.97
Arduino Mini 3.3 V       £2.58
nRF24L01+                 £0.99   (choose the black + version)
A capacitor + cables   pretty much free, say £1

which comes to a total of £12.54 per unit!

Plus one computer connected node, or a raspberry pi with a nRF24L01 to receive the transmissions from all the energy meters.

Arduino and RF24.h
As mentioned in previous blog-posts I have worked quite allot with the nRF24L01 and AVR's, writing my own libraries and so on. But since this is my first Arduino-project I wanted to learn how to import and use other peoples libraries. Since I am still a newbie in programming, I always have to learn everything from scratch, and nothing ever works as supposed to when I try to follow a tutorial...


I started out by setting up two Arduino Nanos according to this guide and running the example code at the bottom of that page, and as expected - it didn't work. 



Debugging
1. Do I have a working SPI-connection?
I had followed the explanation in the guide i linked to above, on how to install the RF24.h-library and it all seamed to work, I definitely had a working SPI-connection between the Arduino and the nRF since I could print out all the registers, and modifying them also worked...

Took me a while to figure out that I had to download and include the file "printf.h" and call "printf_begin();" to print out data from the nRF to the serial monitor... and why, why, why are they using the "protected" attribute  for many of the functions??? For example get_status is a very useful debug-function and should not be protected!

2. Am I using the correct hardware setup? 
As always I hadn't used the exact components as the instructions said, in my drawer I could only find one 47 uF 24 V  and one 100 uF 16 V capacitors. Well in the guide it sais:
"Connect a .3.3 uF to 10 uF (MicroFarad) capacitor directly on the module from +3.3V to Gnd (Watch + and - !) [Some users say 10 uF or more..]"
And I read 10 uF or more....

Anyways, I thought that this should work, since I have used these capacitors before on the nRF, but not with this library and not with Arduino...

3. I found a working code
Yay, suddenly i found a working code, the "pingpair" example that comes with the NRF.h-library worked with my setup!

4. Why does only Pingpair-code work? 
I started stripping the Pingpair-code of its components, and found that my setup was only working when it got into receiving mode in between every transmission... strange, but keeping in mind that I was using bigger capacitors I figured it had something to do with the capacitors not have time enough to recharge/discharge.

I think this is what happened:
When the Arduino calls the "Write" function, the library runs the "startWrite"-function which powers up the nRF and has a predefined delay of 150 us (wait for the nRF to power up) before it starts transmitting the data.
It turned out that this delay was not enough for my setup, so when I changed this to 1000 us (1 ms), the code worked like a charm even without the receiving functions in between! To do this modification, I opened the RF24.cpp-file (in the arduino Sketchbook libraries folder) with notepad, changed the delay, and saved the file.



Arduino Mini
Just as I managed to get a working Arduino code for the nRF, two Arduino Mini 3.3 V landed in my postbox, awesome timing!


One little problem; the Arduino Mini does not come fitted with an USB to Serial-chip to enable programming over USB.... luckily for me I had an USB to Serial adapter laying around (used for debugging AVR's, as I wrote about in this tutorial-post) that I could use to program the Arduino.

Here's a pic of when I have soldered an nRF to the Arduino and uploading code with the USB to COM adapter via a breadboard (out of sight) so the colored cables does not match the pins...


Off course this didn't work straight away either, I found out that when using this kind of FTDI-adapter you have to press the reset-button on the Arduino Mini just when the Arduino-IDE starts to upload the code to get it working! A better buy would be one of these which comes with an automatic reset-pin ("DTR").

I soldered the nRF to the Arduino, and glued them together with some hot-glue, which was also used to attach the unit to the power meter. Plenty of unoccupied room in the meter behind the LCD, and perfect position for a wireless transmitter!


Here you have the wire diagram: 

I started off by just uploading a simple transmission code on the Arduino mini, that would send a dummy byte once a second to confirm a working setup. I  soldered everything together,  plugged the meter into an outlet and kept my fingers crossed as I watched the Arduino-Serial monitor connected to the receiving unit, and.... noting (of course!)

After several hours of debugging, (I thought I had burnt the nRF by hooking it up directly to the power-meters VCC-pin)  It turned out had I accidentally  uploaded a non-working code to the Arduino Mini.... FAIL!!!

I had cleaned up my working code, and shifted some parts around, it seems like you can't open the writing/reading-pipes on the nRF before you set the datarate/payloadsize/PALevel...

Anyway, the setup I found working is grabbing the power directly from the battery (3.6 V soldered to the underside of the PCB) rather than the VCC-cable (which i think is a bit flaky, and is connected to the RAW-pin on the Arduino, which has a built in 3,3 V regulator. I'm not sure this modification is necessary, but it ensures that the nRF and the Arduino gets 3.3 V. (The pictures above are not connected to RAW, but the Arduino's 3.3 V)

Here's whats transmitted to the computer connected Arduino and printed in the Serial monitor:


I have spent some time looking at ways to store and plot this data in the cloud. One interesting approach is to send the data to a website like http://emoncms.org/ and use there ready to use energy-viewing graphs. With the help of a small python-script I wrote, I can easily send the data from my raspberry pi-server to my account on there website where I have the option of making graphs.

I have also been working in the program called "Processing" which is pretty much the same as Arduino-IDE but for graphing and doing stuff with the data.
I have so far programmed a working graph that shows the data output from up to 6 wireless energy meters, it  also logs the data with timestamp to a csv-file. See the processing-code at the bottom.


Above you see a screenshot of when I have plugged in two energy meters (1 and 2). Nr 1 shows a soldering station which i obviously changed the power on allot during the readings. Nr 2 is a 4-step lamp that i flickered from 3 to 0 to 1 to 2 to 3. as you see i didn't stop at 0 for a very long time, so the graphed mean value stopped at ~10W.

You might wounder why the red and green line (nr 1) sometimes differ? That's because I have the meter to transmit the average=red and the maximum=green power readings on every third power reading. This interval is easily changed by typing 1:1 or 1:4 to change the interval on meter 1 from to 1 or to 4 readings in between transmissions.

I had a hard time figuring out how to transmit this new interval from the computer nrf to the meter, because if I in between every transmission changed the nRF to a receiver, the power consumption would cause the whole meter to stop working.

This time I had to do some serious thinking, and I ended up using the possibility to alter the autoAck-payload. A function that normally sends an "OK" from the receiving nrf back to the transmitting nRF to confirm the transmission. I found out how to alter this value to send something like a "2" instead, or some other integer that would be a new interval. This was exactly what I needed, See the code at the bottom!

Her's the working Arduino code, first for the Energy Meter then for the computer connected receiver-Arduino. At the very bottom you have the processing code:

/*
Reads voltage and power from China-style energy meter and sends it to nRF24L01+.
Collecting data from meter by eavesdropping on the MOSI-line (master in slave out)
between the energy monitoring chip (ECH1560) and the main processor
Meter Arduino
GND (Brown) GND (2nd from the end of the meter-board)
VCC (3.6V) RAW (Connect to battery "+" under meter-board)
CLK (Green) D2 (INT0) (5th from the end of the meter-board)
SDO (Blue-white) D5 (6th from the end of the meter-board)
nRF24L01+ Ardiono
GND (square) GND
VCC 3,3V (mini = VCC)
CE 9
CSV 10
SCK 13
MOSI 11
MISO 12
*/
#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include "printf.h"
//NRF-setup:
#define CE_PIN 9
#define CSN_PIN 10
//Energy meter setup:
const int CLKPin = 2; // Pin connected to CLK (D2 & INT0)
const int MISOPin = 5; // Pin connected to MISO (D5)
// Set up nRF24L01 radio on SPI bus plus pins 9 & 10
RF24 radio(CE_PIN, CSN_PIN); // Create a Radio
// Radio pipe addresses for 1 node to communicate.
//const uint64_t PipeAddress = 0xAABBCCDD11LL; //5-byte address "LL" is for long
const uint64_t pipes[] = { 0xAABBCCDD11LL}; //Transmitting address (Last 2 numbers are number on energy-meter)
//EnergyMeter-variables
//All variables that are changed in the interrupt function must be volatile to make sure changes are saved.
volatile int Ba = 0; //Store MISO-byte 1
volatile int Bb = 0; //Store MISO-byte 2
volatile int Bc = 0; //Store MISO-byte 2
float U = 0; //voltage
float P = 0; //power
float ReadData[3] = {0, 0, 0}; //Array to hold mean values of [U,I,P]
int AverageMax = 5;
volatile long CountBits = 0; //Count read bits
volatile int Antal = 0; //number of read values (to calculate mean)
volatile long ClkHighCount = 0; //Number of CLK-highs (find start of a Byte)
volatile boolean inSync = false; //as long as we ar in SPI-sync
volatile boolean NextBit = true; //A new bit is detected
void SendToComputer(void); //initiate transmitt-function
void setup(void)
{
//debug over Serial
Serial.begin(57600);
//Setting up interrupt ISR on D2 (INT0), trigger function "CLK_ISR()" when INT0 (CLK)is rising
attachInterrupt(0, CLK_ISR, RISING);
//Set the CLK-pin (D5) to input
pinMode(CLKPin, INPUT);
//Set the MISO-pin (D5) to input
pinMode(MISOPin, INPUT);
// Setup and configure nrf radio see: http://maniacbug.github.io/RF24/classRF24.html
radio.begin();
//
//********* Optional settings for nrf below see: http://maniacbug.github.io/RF24/classRF24.html
//
// increase the delay between retries & # of retries
radio.setRetries(15,15);
// reduce the payload size. (3 floates = 3*4=12 Bytes)
radio.setPayloadSize(12);
//Set speed of transmission (250kbps only works on the "+"-version!!! slower increases range!
radio.setDataRate(RF24_250KBPS);
//Set Power Amplifier (PA) level to high to increase range!
radio.setPALevel(RF24_PA_HIGH);
//Automatically receive data when sending something
radio.enableAckPayload();
//
//********* End of optional settings*********
//
//Addresses has to be set last!
//Transmitter address
radio.openWritingPipe(pipes[0]);
//I don't have to set an receiver address, because the auto ack will automatically receive an payload if i need to send anything to this meter!
}
void loop(void)
{
//do nothing until the CLK-interrupt occures and sets inSync=true
if(inSync == true){
CountBits = 0; //CLK-interrupt increments CountBits when new bit is received
while(CountBits<40){} //skip the uninteresting 5 first bytes
CountBits=0;
Ba=0;
Bb=0;
while(CountBits<24){ //Loop through the next 3 Bytes (6-8) and save byte 6 and 7 in Ba and Bb
if(NextBit == true){ //when rising edge on CLK is detected, NextBit = true in in interrupt.
if(CountBits < 9){ //first Byte/8 bits in Ba
Ba = (Ba << 1); //Shift Ba one bit to left and store MISO-value (0 or 1) (see http://arduino.cc/en/Reference/Bitshift)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Ba |= (1<<0); //changes first bit of Ba to "1"
} //doesn't need "else" because BaBb[0] is zero if not changed.
NextBit=false; //reset NextBit in wait for next CLK-interrupt
}
else if(CountBits < 17){ //bit 9-16 is byte 7, stor in Bb
Bb = Bb << 1; //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bb |= (1<<0); //changes first bit of Bb to "1"
}
NextBit=false; //reset NextBit in wait for next CLK-interrupt
}
}
}
if(Bb!=3){ //if bit Bb is not 3, we have reached the important part, U is allready in Ba and Bb and next 8 Bytes will give us the Power.
Antal += 1; //increment for mean value calculations
//Voltage = 2*Ba+Bb/255
U=2.0*((float)Ba+(float)Bb/255.0);
//Power:
CountBits=0;
while(CountBits<40){}//Start reading the next 8 Bytes by skipping the first 5 uninteresting ones
CountBits=0;
Ba=0;
Bb=0;
Bc=0;
while(CountBits<24){ //store byte 6, 7 and 8 in Ba and Bb & Bc.
if(NextBit == true){
if(CountBits < 9){
Ba = (Ba << 1); //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Ba |= (1<<0); //changes first bit of Ba to "1"
}
NextBit=false;
}
else if(CountBits < 17){
Bb = Bb << 1; //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bb |= (1<<0); //changes first bit of Bb to "1"
}
NextBit=false;
}
else{
Bc = Bc << 1; //Shift Bc one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Bc[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bc |= (1<<0); //changes first bit of Bc to "1"
}
NextBit=false;
}
}
}
//Power = (Ba*255+Bb)/2
P=((float)Ba*255+(float)Bb+(float)Bc/255.0)/2;
//Voltage mean
ReadData[0] = (U+ReadData[0]*((float)Antal-1))/(float)Antal;
//Power mean
ReadData[1] = (P+ReadData[2]*((float)Antal-1))/(float)Antal;
//Power max
if(P>ReadData[2]){
ReadData[2] = P;
}
//every 5th read-out ~every 5th second, we send the mean value data to the nrf24l01-transmitter
if(Antal>=AverageMax){
//Send the data to the computer
bool ok = radio.write( ReadData, sizeof(ReadData) );
if (ok){
Antal=0; //reset mean-value counter after successfull transmission ~10s
ReadData[0]=0;
ReadData[1]=0;
ReadData[2]=0;
//This is an awesome feature, if "radio.enableAckPayload()" is enabled, then we may have got somethig in return that we can use:
//did we get any data in return when sending the bytes??
if ( radio.isAckPayloadAvailable() )
{
radio.read(&AverageMax,sizeof(AverageMax));
}
}
}
inSync=false; //reset sync variable to make sure next reading is in sync.
}
if(Bb==0){ //If Bb is not 3 or something else than 0, something is wrong!
inSync=false;
Serial.println("Disconnected");
}
}
}
//Function that triggers whenever CLK-pin is rising (goes high)
void CLK_ISR(){
//if we are trying to find the sync-time (CLK goes high for 1-2ms)
if(inSync==false){
ClkHighCount = 0;
//Register how long the ClkHigh is high to evaluate if we are at the part wher clk goes high for 1-2 ms
while(digitalRead(CLKPin)==HIGH){
ClkHighCount += 1;
delayMicroseconds(30); //can only use delayMicroseconds in an interrupt.
}
//if the Clk was high between 1 and 2 ms than, its a start of a SPI-transmission
if(ClkHighCount >= 33 && ClkHighCount <= 67){
inSync = true;
}
}
else{ //we are in sync and logging CLK-highs
//increment an integer to keep track of how many bits we have read.
CountBits += 1;
NextBit = true;
}
}
// vim:cin:ai:sts=2 sw=2 ft=cpp

Here's the code for the receiving Arduino (connected to computer via USB)
#include <SPI.h>
#include "nRF24L01.h"
#include "RF24.h"
#include "printf.h" //Activate for NRF-debug (printf_begin(); in setup() followed by radio.printDetails();)
#define CE_PIN 9
#define CSN_PIN 10
//
// Hardware configuration
//
// Set up nRF24L01 radio on SPI bus plus pins 9 & 10
RF24 radio(CE_PIN, CSN_PIN); // Create a Radio
// Radio pipe addresses 1 node to communicate.
//const uint64_t Address = 0xAABBCC22LL; //5-byte address "LL" is for long (if more than one node:)
//const uint64_t pipes[2] = { 0xAABBCC11LL, 0xAABBCC22LL }; //Pipes 1-5 must share the first 4 bytes. Only the least significant byte should be unique!
const uint64_t pipes[3] = { 0xBABBCCDD00LL, //Writing pipe (not used)
0xAABBCCDD11LL, //Meter A's writing pipe
0xAABBCCDD22LL //Meter B's writing pipe
}; //First letter is address to energ-meter
float ReadData[3] = {0, 0, 0};
uint8_t TempStatus;
uint8_t CH;
uint8_t data[2];
void setup(void)
{
Serial.begin(57600);
//printf_begin();
Serial.println("Start: ");
//
// Setup and configure rf radio
radio.begin();
//
//********* Optional settings for nrf below see: http://maniacbug.github.io/RF24/classRF24.html
//
// increase the delay between retries & # of retries
radio.setRetries(15,15);
// reduce the payload size. (3 floates = 3*4=12 Bytes)
radio.setPayloadSize(12);
//Set speed of transmission (250kbps only works on the "+"-version!!! slower increases range!
radio.setDataRate(RF24_250KBPS);
//Set Power Amplifier (PA) level to high to increase range!
radio.setPALevel(RF24_PA_HIGH);
//Awesome feature that lets us send a package in return when receiving something without changing to transmitter!
radio.enableAckPayload();
//
//********* End of optional settings*********
//
//Addresses has to be set last!
//radio.openWritingPipe(pipes[0]);
radio.openReadingPipe(1,pipes[1]);
radio.openReadingPipe(2,pipes[2]);
//Start listening for incoming data
radio.startListening();
//
// Dump the configuration of the rf unit for debugging
//
//read_register(CONFI); //read out the status register to decide which channel that's transmitting data //change RF24.h in libraries (remove "public:", "protected:" and change "private:" to "public:) to use this function!
//Serial.println(radio.get_status(),BIN);
//Serial.println(radio.read_register(RF_SETUP),BIN);
Serial.println("Type: 2:3 to change the intervall of meter 2 to ~3s");
//radio.writeAckPayload( 1, &AverageMax, sizeof(AverageMax) );
//radio.writeAckPayload( 2, &AverageMax, sizeof(AverageMax) );
}
void loop(void)
{
// if data is received to the nRF
if ( radio.available() )
{
// Dump the payloads until we've gotten everything
bool done = false;
while (!done)
{
Serial.println(" ");
//Serial.println(radio.get_status(),BIN);
// read out the status register to decide which channel that's transmitting data
//change RF24.h in libraries (remove "public:", "protected:" and change "private:" to "public:) to use this function!
CH = 0;
CH = ((radio.get_status() & 0b00001110) >> 1); //extract bit 1-3 (the channels) to CH and move them one step to right to get it in decimal
// Fetch the payload, and see if this was the last one.
done = radio.read( ReadData, sizeof(ReadData) );
//Print out details
Serial.print("Energy meter: ");
Serial.println(CH);
//When meter reads 0W it sometimes shows ~6000W
if(ReadData[2]<4000){
Serial.print(ReadData[0],0);
Serial.println(" V");
Serial.print(ReadData[1],1);
Serial.println(" W");
Serial.print(ReadData[2],2);
Serial.println(" W-Max");
}
else{
Serial.print(ReadData[0],0);
Serial.println(" V");
Serial.print(0.0,0);
Serial.println(" W");
}
delay(20);
//Reset STATUS-register:
//radio.write_register(STATUS, _BV(RX_DR) | _BV(TX_DS) | _BV(MAX_RT) );
}
}
}
//Interrupt ocures whenever you type anything in the serial-monitor.
//To change the data sending interval of an energy meter, in the serial monitor type:
//2:3
//to change the channel 2-energy meter to ~3s interval.
void serialEvent() {
while (Serial.available()) {
// Reads the the bytes until it reaches an non-integer value ":"
int CH = Serial.parseInt();
byte skipp = Serial.read();
int AverageMax = Serial.parseInt();
if(Serial.available()==false && CH >0 && CH < 6 && AverageMax >0 && AverageMax <10000){
// Add an ack packet for the next time around
radio.writeAckPayload( CH, &AverageMax, sizeof(AverageMax) );
Serial.print("Intervall on meter: ");
Serial.print(CH);
Serial.print(" will change to: ~");
Serial.print(AverageMax);
Serial.println("s on next transmission!");
}
else{
while (Serial.available()) {
skipp = Serial.read();
}
Serial.println("Wrong format! Type: 2:3 to change the intervall of meter 2 to ~3s");
}
}
}
// vim:cin:ai:sts=2 sw=2 ft=cpp

And finally the Processing code that can be used to read and write to the computer connected Arduino through its serial connection (over USB)
import processing.serial.*;
Serial myPort; // Create object from Serial class
String val; // Data received from the serial port
//print to csv-file
PrintWriter output;
long xPos = 1; // horizontal position of the graph
//int xLast[] = new int[6];
int yPos = 0;
int xMax = 600;
int yMax = 600;
int vmax = 250;
int pmax = 500;
int newPmax=0;
long lastupdatedXvalue = 0;
int pmmax = pmax;
int Meter = 1;
int IntValue=0;
float Last_V = 0.0;
float Last_P = 0.0;
float Last_Pmax = 0.0;
boolean Error = false;
float curVal=0;
int curElevation=0;
String SerialString = "";
String typing = "";
int RGB[][] = new int[][] {
{
255, 0, 0,
255, 0, 0,
0, 150, 0,
}
,
{
255, 220, 230,
255, 0, 0,
170, 25, 255,
}
};
//ArrayList<ArrayList<Float>> V = new ArrayList<ArrayList<Float>>(6);
TwoDArrayList V;
TwoDArrayList P;
TwoDArrayList PMax;
TwoDArrayList xVals = new TwoDArrayList();
movingLabels Label[][] = new movingLabels[2][6];
//ArrayList<ArrayList<Float>> P = new ArrayList<ArrayList<Float>>(5);
//ArrayList<ArrayList<Float>> PMax = new ArrayList<ArrayList<Float>>(5);
//ArrayList P = new ArrayList();
//ArrayList PMax = new ArrayList();
String label;
float[] markers;
String portName = "";
void setup()
{
// List all the available serial ports
println(Serial.list());
//Sets current Serial-port to the arduino port (the last in the list!?)
portName = Serial.list()[Serial.list().length-1]; //change the "Serial.list().length-1" to a 1 or 2 etc. to match your port
//Create Serial object to use for comunication with the Arduino with the correct baudrate (Energy meter=57600)
myPort = new Serial(this, portName, 57600);
//create a csv-file and folder with timestamp-name to stop it from overwriting files...
output = createWriter("Logged Data/EnergyMeter_" + year() + "-" +month() + "-" + day() + "_" + hour() + "." + minute() + ".csv");
//create new instances of a nested arraylist-object (see tab "Arraylist")
V = new TwoDArrayList();
P = new TwoDArrayList();
PMax = new TwoDArrayList();
// set the window size:
size(xMax, yMax);
// set inital background to gray
background(0);
//A serialEvent() is generated when a newline character is received :
myPort.bufferUntil('\n');
xPos=0;
drawTitle();
//Label[2]=new movingLabels(xPos, 200.0, Integer.toString(xPos) + " V");
}
void draw()
{
//Wait for a serial event to trigger...
}
//Interrupt that triggers whenever data is received on the serial port.
void serialEvent (Serial myPort) {
//if error occures, do not stop code...
try {
// get the Serial-ASCII string:
String inString= myPort.readStringUntil('\n');
println(inString); //debug
if (inString != null) {
// trim off any whitespace before and after the data (if exists)
inString = trim(inString);
//The data comes in 4 separate transmissions, first energy meter number, then V then W than W-Max
//now check which one we are receiving:
if (inString.indexOf("Energy")>=0) //If the String "Energy" is found, its the Energy meter number "Energy Meter: x"
{
//Remove the "Energy Meter: " to get the float containing the number
//print("Mätare: ");
inString = inString.replaceAll("Energy meter: ", "");
Meter = Integer.parseInt(inString.trim());//Float.parseFloat(inString);
//increment x-value
xPos=millis()/100; //10 lines per second
//Setts the actual value, before fitting it into the graph.
} else if (inString.indexOf(" V")>=0 && V.getSize(Meter)==PMax.getSize(Meter) && Meter<7 && Meter>0) //If the String " V" is found, its the voltage string: "xxx V"
{
//Remove the " V" to get the float containing the data
inString = inString.replaceAll(" V", "");
IntValue = Integer.parseInt(inString.trim());
if (IntValue>0) {
Last_V = float(inString);
ReDraw();
//If we've allready filled 3/4th of the plot-window, start removing data so we dont crash into the wall.
if (xPos >= xMax-100)
{
//ReDraw();
}
xVals.addArr(Meter, (float)xPos);
stroke(RGB[Meter-1][0], RGB[Meter-1][1], RGB[Meter-1][2]);
Error=false;
//If this is a valid reading IntValue>200 (~230 expected) to skip error-values
if (IntValue>200)
{
//voltage converted to a scale from (0 to vmax) as (0 to height of the graph*0,8)
curVal=map(IntValue, 0, vmax, 0, height*0.8);
//Add the value to the V-object
V.addArr(Meter, curVal);
} else if (V.getSize(Meter)>0) //Error and not first valueA
{
Error=true;
curVal=V.getLast(Meter);
V.addArr(Meter, V.getLast(Meter));
} else //Error and first value =>put a zero as first recorded value
{
curVal=0;
V.addArr(Meter, curVal);
}
//Check if this is the first added value?
if (V.getSize(Meter)==1)
{
//Draw the starting line from current xPos and y=V(0) to itself (make a dot)
line(xPos, height-V.getArr(Meter, 0), xPos, height-V.getArr(Meter, 0));
//Create a label-object for the line that hoovers 10px over line (first index of "Label" is 0=V,1=Pmax,2=P, secound index is Meter)
Label[0][Meter]=new movingLabels(xPos, height-V.getArr(Meter, 0)-10, inString + " V");
} else {
//Draw a line from the second last xVals-value to the new xPos-value (last xVals-value)
line(xVals.getLast(Meter, 1), height-V.getLast(Meter, 1), xVals.getLast(Meter), height-V.getLast(Meter));
//print the label:
Label[0][Meter].drawText(xPos-10, height-curVal-10, Meter + String.format(": %.0f", Last_V)+"V");
}
//output.println("V");
}
}
//now do the same with W-Max and W (note the "" for string and '' for char!
else if (inString.indexOf("W-Max")>=0 && PMax.getSize(Meter)<P.getSize(Meter)) // Max power "xx.x W-Max"
{
inString = inString.replaceAll(" W-Max", "");
Last_Pmax = float(inString);
stroke(RGB[Meter-1][6], RGB[Meter-1][7], RGB[Meter-1][8]);
//skip error-values
if (Last_Pmax<4000 && Error == false)
{
curVal= map(Last_Pmax, 0, pmmax, 0, height*0.8);
//Add the voltage-float converted to a scale from 0 to vmax as 0 to height of the graph*0,8
PMax.addArr(Meter, curVal);
} else if (PMax.getSize(Meter)>0) {
Error=true;
curVal=PMax.getLast(Meter);
PMax.addArr(Meter, PMax.getLast(Meter));
} else {
Error=true;
curVal=0;
PMax.addArr(Meter, curVal);
}
//Check if this is the first added value?
if (PMax.getSize(Meter)==1) {
//Draw the starting line from x=10 and y=V(0) to itself (make a dot)
line(xPos, height-PMax.getArr(Meter, 0), xPos, height-curVal);
} else {
//Draw a line from the last value to the new value
line(xVals.getLast(Meter, 1), height-PMax.getLast(Meter, 1), xVals.getLast(Meter), height-PMax.getLast(Meter));
}
//output.println("Wmax");
//Print all the values to a csv-file (see output-tab)
PrintToCSVFile();
} else if (inString.indexOf(" W")>=0 && inString.indexOf("Max")<0 && P.getSize(Meter)<V.getSize(Meter)) //Average Power "xx.x W"
{
inString = inString.replaceAll(" W", "");
Last_P = float(inString);
stroke(RGB[Meter-1][3], RGB[Meter-1][4], RGB[Meter-1][5]);
//skip error-values either caught here, or by the voltage-readings.
if (Last_P<=4000 && Error == false)
{
curVal=map(Last_P, 0, pmax, 0, height*0.8);
//Add the voltage-float converted to a scale from 0 to vmax as 0 to height of the graph*0,8
P.addArr(Meter, curVal);
//Add kWh
P.addkWh(Meter, Last_P);
} else if (P.getSize(Meter)>0)
{
Error=true;
curVal=P.getLast(Meter);
P.addArr(Meter, P.getLast(Meter));
} else //this is the first reading, and it is wiered.
{
Error=true;
curVal=0;
P.addArr(Meter, curVal);
}
//Check if this is the first added value?
if (P.getSize(Meter)==1) {
//Draw the starting line from x=10 and y=V(0) to itself (make a dot)
line(xPos, height-P.getArr(Meter, 0), xPos, height-curVal);
Label[1][Meter]=new movingLabels(xPos, height-curVal-10, "W");//Float.toString(P.getLast(Meter)) + " V");
} else {
//Draw a line from the last value to the new value
line(xVals.getLast(Meter, 1), height-P.getLast(Meter, 1), xVals.getLast(Meter), height-P.getLast(Meter));
Label[1][Meter].drawText(xPos+5, height-curVal-10, Meter + String.format(".\n%.1f", Last_P)+"W\n" + String.format("%.4f", P.getkWh(Meter)) + "kWh");//Float.toString(P.getLast(Meter)) + " W");
}
//output.println("W");
}
}
}
catch(RuntimeException e) {
print("Här: ");
println(e);
delay(1000);
myPort = new Serial(this, portName, 57600);
}
}
//Function that triggers when a key is pressed, that sends data to the Arduino over serial.
void keyPressed() {
// If the return key is pressed, save the String, do something with it, clear it
if (key == '\n' ) {
//type eg: 2:1 to set the transmission intervall to 1s on the 2'nd meter.
if (SerialString.indexOf(":")>=0) { //see if the string contained ":"
//Send string to Arduino:
myPort.write(SerialString);
} else if (SerialString.indexOf("z")>=0) { //if you want to change the zoom on the power-readings, type
//example: type "z1800" to set it to pmax=1800W => screen height
try {
//extract the number-part from the string and try and convert it to an integer:
newPmax=int(SerialString.replaceAll("z", ""));
ReDraw();
}
catch(Exception e) {
//newPmax=0;
}
}
//redraws the whole graph.
//ReDraw();
// clear the string
SerialString = "";
} else {
// Each character typed by the user is added to the end of the String variable.
SerialString = SerialString + key;
drawTitle();
//The string is printed on the screen everytime the Label is uated...
}
//ReDraw();
}
//******************************************************New Tab here****************************************************//
/*This class is creating nested arraylists
Theloat in my case, but can be used by all objects
To create an nested arraylist:
//Create a public variable-list
TwoDArrayList = X;
//In code, make a new instance of the list
X = new TwoDArrayList();
//Then
X.addArr(2,34); //Adds "34" to the last position of array 2
X.setArr(2,3,34); //Sets "34" to array 2, position 3.
X.getArr(2,3); //Returns value from array 2, position 3.
*/
class TwoDArrayList<T> extends ArrayList<ArrayList<T>> {
long lastX[] = new long[6];
float kWh[][]= new float[6][2];
public void setLastX(int index, long _lastX) {
lastX[index]=_lastX;
}
public long getLastX(int index) {
if (lastX[index]==0) {
lastX[index]= xMax-100;
}
return lastX[index];
}
public void addkWh(int index, float Pmedel) {
//E=P*dt
kWh[index][0]+=Pmedel*(millis()-kWh[index][1])/(1000*3600)/1000; // /ms /s per h /kW in W
kWh[index][1]=millis();
}
public float getkWh(int index) {
return kWh[index][0];
}
//Add element on last position of inner list "index"
public void addArr(int index, T element) {
while (index >= this.size ()) {
this.add(new ArrayList<T>());
}
this.get(index).add(element);
}
//Add element on specific position of index and index2
public void setArr(int index, int index2, T element) {
while (index >= this.size ()) {
this.add(new ArrayList<T>());
}
ArrayList<T> inner = this.get(index);
while (index2 >= inner.size ()) {
inner.add(null);
}
inner.set(index2, element);
}
//return value from index position
public float getArr(int index, int index2) {
return (Float)this.get(index).get(index2);
}
//return size from index position
public int getSize(int index) {
if (this.isEmpty()) {
return 0;
} else if (index>this.size()-1) {
return 0;
} else if (this.get(index).isEmpty()) {
return 0;
} else {
return (Integer)this.get(index).size();
}
}
//return last value without offset
public float getLast(int index) {
return (Float)this.get(index).get(this.get(index).size() -1);
}
//return last value with offset
public float getLast(int index, int offset) {
return (Float)this.get(index).get(this.get(index).size() -1 -offset);
}
//
public void Remove(int index, int index2) {
if (this.get(index).isEmpty()==false) {
this.get(index).remove(index2);
}
}
}
//******************************************************New Tab here****************************************************//
void drawTitle() {
//background(0);
fill(255, 255, 255);
textAlign(LEFT);
String title = "Energy Meter";
textSize(20);
text(title, 20, 20);
textSize(15);
text("Zoom: " + pmax + " W", 20, 50);
text(SerialString, 250, 20);
}
void drawLabel(int x, int y, String val, String unit) {
fill(255, 255, 255);
textSize(10);
textAlign(LEFT);
String title = val + ' ' + unit;
text(title, x, y);
}
class movingLabels {
float x, y, xOld, yOld;
String s;
String sOld="";
movingLabels (float _x, float _y, String _text) {
//This function is the 'constructor'.
//It will get called when you create a new
//movingText object
x = _x; //Set x to the first argument
y = _y; //Set y to the second argument
s = _text; //Set our string to the 3rd argument
}
public void drawText(float _x, float _y, String _text) {
s=_text;
x=_x;
y=_y;
textSize(10);
textAlign(LEFT);
//Start by writing over the old text with black:
fill(0);
for (int i=0; i<10; i++) {
//text(sOld, xOld, yOld);
}
textSize(10);
//Now print the new text in white
fill(255, 255, 255);
textLeading(10); //enable new line '\n'
text(s, x, y);
sOld=s;
xOld=x;
yOld=y;
drawTitle();
}
}
void YLabel() {
fill(255, 255, 255);
textSize(10);
textAlign(RIGHT);
stroke(255,255,255);
strokeWeight(1);
int Intervall = pmax/20;
int HuvudLinje = Intervall*5;
for (float v = 0; v <= pmax; v += Intervall) {
if (v % Intervall == 0) { // If a tick mark
float y = map(v, 0, pmax, height,height*0.2);
//=map(Last_P, 0, pmax, 0, height*0.8);
if (v % HuvudLinje == 0) { // If a major tick mark
float textOffset = textAscent()/2; // Center vertically
if (v == 0) {
textOffset = 0; // Align by the bottom
} else if (v == height*0.8) {
//textOffset = textAscent(); // Align by the top
}
text(floor(v), 20, y + textOffset);
line(35, y, width, y); // Draw major tick
//line(plotX1-2, y+9, plotX1, y+9); //line to draw midle lines
} else {
line(40, y, 45, y); // Draw minor tick
}
}
}
}
//******************************************************New Tab here****************************************************//
void PrintToCSVFile() {
//String to export to csv-file with timestamp:
//csv-files opened in Swedish Excel automatically separate colums by: ';', in english version it's: ','
String Temp = year() + "-" + month() + "-" + day() + ";";
Temp += hour() + ":" + minute() + ":" + second() + ";";
//jump some colums to separate the different meters:
for (int i=1; i<Meter; i++) {
Temp += ";;;;;;;";
}
Temp += "Energy Meter: " + Meter + ";";
Temp += String.format("%.0f", Last_V) + ";V;";
Temp += String.format("%.1f", Last_P) + ";W;";
Temp += String.format("%.1f", Last_Pmax) + ";W";
//put the string in output-buffer
output.println(Temp);
//Execute the writing to the file...
output.flush();
}
//Not used, but a way of adding separators.
String PrintData(float Data, int Col) {
String TempStr = "";
for (int i=0; i<Col; i++) {
TempStr = TempStr + ";";
}
return TempStr + String.format("%.1f", Data);
}
//******************************************************New Tab here****************************************************//
void ReDraw() {
//if a secound meter starts after we've hit the wall, its empty!
if (V.getSize(Meter)>0) {
// set inital background=clear screen
background(0);
//save current meter to remember which one to add data to later.
int currMeter = Meter;
//put the string in output-buffer
//output.println("getlastX: ;" + xVals.getLastX(Meter) + ";Xpos: ;" + xPos);
//find the offset from last recorded value:
long Xoffset=xPos-lastupdatedXvalue;//xVals.getLastX(Meter);
lastupdatedXvalue=xPos;
//loop through all the meters and if they contain data; meve them back one dX
for (int j=1; j<7; j++) {
Meter=j;
//Check if Meter is not empty
if (V.getSize(Meter)>0) {
//Remove values that have passed the screen on the rest of the meters
while (xVals.getArr (Meter, 0)<-100) {
V.Remove(Meter, 0);
P.Remove(Meter, 0);
PMax.Remove(Meter, 0);
xVals.Remove(Meter, 0);
}
if (xPos>= xMax-100 && newPmax==0) {
//Uppdate all the xVals on j-meter.
for (int i=0; i<xVals.getSize (Meter); i++)
{
xVals.setArr(Meter, i, xVals.getArr(Meter, i) - Xoffset);
}
}
if (newPmax>0) {
for (int i=0; i<P.getSize (Meter); i++)
{ // curVal=map(P, 0, pmax, 0, height*0.8);
P.setArr(Meter, i, P.getArr(Meter, i)*pmax/newPmax);
PMax.setArr(Meter, i, PMax.getArr(Meter, i)*pmmax/newPmax);
}
}
//Set line-color to pink for plotting "V"
stroke(RGB[Meter-1][0], RGB[Meter-1][1], RGB[Meter-1][2]);
//Uppdate all the V-values
for (int i=0; i<V.getSize (Meter)-1; i++)
{
line(xVals.getArr(Meter, i), height-V.getArr(Meter, i), xVals.getArr(Meter, i+1), height-V.getArr(Meter, i+1));
}
//Set line-color to pink for plotting "W-Max"
stroke(RGB[Meter-1][3], RGB[Meter-1][4], RGB[Meter-1][5]);
for (int i=0; i<P.getSize (Meter)-1; i++)
{
line(xVals.getArr(Meter, i), height-P.getArr(Meter, i), xVals.getArr(Meter, i+1), height-P.getArr(Meter, i+1));
}
//Set line-color to pink for plotting "W"
stroke(RGB[Meter-1][6], RGB[Meter-1][7], RGB[Meter-1][8]);
for (int i=0; i<PMax.getSize (Meter)-1; i++)
{
line(xVals.getArr(Meter, i), height-PMax.getArr(Meter, i), xVals.getArr(Meter, i+1), height-PMax.getArr(Meter, i+1));
}
//If this isn't the meter that'll get a new value, draw the lables
if (Meter!=currMeter) {
//Label[0][Meter].drawText(xVals.getLast(Meter), height-V.getLast(Meter)-10, Meter + String.format(": %.0f", map(V.getLast(Meter), 0, height*0.8, 0, vmax))+"V");
Label[1][Meter].drawText(xVals.getLast(Meter)+5, height-P.getLast(Meter)-10, Meter + String.format(".\n%.1f",
map(P.getLast(Meter), 0, height*0.8, 0, pmax))+"W\n" + String.format("%.4f",P.getkWh(Meter)) + "kWh");
}
}
}
Meter=currMeter;
if (newPmax>0) {
pmax=newPmax;
pmmax=newPmax;
newPmax=0;
}
}
//Save the current time
xVals.setLastX(Meter, xPos);
if (xPos> xMax-100) {
//X-value for newest value that'll be added bellow!
xPos = xMax-100;
}
YLabel();
}
view raw EnergyMeter.pde hosted with ❤ by GitHub

Monday, October 20, 2014

Power Plug Energy Meter Hack

It has been way to long ago since I tested my capability of hacking things.

Since i am an energy engineer, I have been looking for a cheap and easy way of monitoring my power consumption. 
I know there are other hackers out there that have already worked on this problem, and I have seen dozens of hacks on smart and dumb house-power meters, but only a few that covers power plug energy meters. 

You have the Tweetawatt - awesome, but not my cup of tee (i prefer to write my own software for AVR or Arduino) and still ~55$ each...
And a guy named Connor Wolf has an awesome project where he builds his own and a video where he tares a few standard power plug meters apart

I have seen how cheap the China-version of the energy meter is (£7,86), and when i saw the tare-apart video where he takes one apart, I went ahead and ordered two pieces of the EU-type (230V 3,6kW). Of course my intention was to convert them to my own cheaper version of the Tweetawatt.


My final goal is to connect them to the internet either via an nRF24L01+  and my rPi-setup, or with an ESP8266 Wifi adapter (if it will ever arrive in the mail box...)

The future goal is to use an home made Android app to graph the data, i'm not quite there jet, but this tutorial describes how I hacked the power meter and successfully got the voltage, current and power readings to an arduino using interrupts on the CLK. 

The meters showed up last week, and the first thing i did was to open the cover of one of them. 


The guts looked promising since it is very similar to the one in Connor Wolfs video with the 3,6 V battery and the ribbon cable between the two circuit boards. The differences i can see compared to the 110 V version is the big blue capacitor.

The reason I started this project from the first place was because I had seen the ribbon cable labels in the video, so I was very satisfied when I confirmed that the 230 V version also came with the labeled ribbon cable between the power meter and the main processor which sits under the brown circuit board.

The ribbon is labeled: 
VCC, SGND, FREQ, CLK, SDO and SDI as seen here:


I tapped into all of the 7 wires, (7?) yes there are 7 wires, only 6 labeled. closed the case, and plugged it into the wall.

Before i hooked it up to my awesome £6, 8-channel, 24 MHz logic analyzer and started testing it in the logic analysing software, I firs checked all the cables with a multimeter to see that none of them was connected to mains (this video shows that the Kill-a-Watt meter has 110 V on the ribbon cable strangely enough). But the China version was safe on all 7 wires and the five which weren't VCC or GND  got its own channel on the logic analyzer:

###WARNING!!! I'm not an expert in HVAC and there are lots of knowing people that read this article on Hackaday.com and informed me that hooking up the logical analyser like this is an terrible idea! It seems like the energy meters DC-line is not grounded, but instead use Neutral as ground, which can be very different from your computers USB-ground... DO NOT USE MY SETUP, It can be both dangerous and harmful to the computer!

If you want to test the SPI on a non-grounded device they have a lot of suggestions on how this should be done, optical isolation sounds pretty smart (maybe there are even optically isolated USB-hubs you could use?!) I guess I was lucky not to blow up my computer, or my self...


I must admit that this was the first time I have ever attempted to sniff a data communication before, so I had to do a little research. I recognized the CLK as the clock wire in SPI, and guessed that the SDO and SDI was the same as MISO and MOSI but where was the SS (chip select) wire?

My hope was that maybe SPI can work without chip select when there is only one slave that listens, but that would make it heard to know when a transmission starts and end!? how does it sync?

Well, it turns out that I was right, This is the output on a run with nothing connected but the meter:


(click picture for larger version)

Yey, This confirmed my theory and it showed that the FREQ-pin was giving a 50 Hz signal, not at all involved in the SPI communication (nope it's not the SS-line). and that the un-labeled cable was the same as the VCC-labeled pin (high = 3,6V)

This project has improved my analyzing skills allot, and I had to learn how to set up the analyzer to debug the SPI-signal (great SPI-info)

To read this scatter as SPI you need to define the start (where to read the first bit in a byte from)
1. press T1 or hit 1 on keyboard
2. put marker in between SPI-signals (where it's obviously not in the middle of sending a byte)
3-4. Add an Analyzer, choose SPI



Next step is setting up the SPI-analyzer:
1. Press settings
2. zoom in on the first byte, and try and figure out what settings that is used. (see pic under this as well)

Start by "Re-run starting at marker T1" as in picture bellow.
I found that my data is read when CLK is rising "Trailing Edge" and comes in sets of 8 bits (1 byte). 
Note the last MOSI-byte going low, only catched by the trailing edge of clk=>trailing edge
This is how the bits in a byte are interpreted on trailing edge: 


When the CLK goes high, the status on the MOSI and MISO are converted to either 1 or 0. After 8 bits, you have a byte which can be translated to decimal value, as seen above:
MOSI = 1111 1110 => decimal 254
MISO = 0001 0000 => decimal 16

At this time, there was one happy geek in the house!

Decipher the data

Now I had figured out how to sniff the data communication, I still had no idea of what, and in what format the data was sent.

I figured that my best chance of decoding the data would be to sample lots of data and then compare it. So i started sniffing the setup when connecting my soldering station which was perfect since it has the ability to choose different power settings, and for heavy load i used a 1,8 kW water heater.

When comparing the data, it was quite clear that there is not much going on here.The data is sent in chunks of 70 packages at a time, followed by a 47 ms delay. Each package contains 8 bytes, and luckily for me, the first 68 package seems to be the same every time, independent of the wattage reading and they all look like this:

Byte MOSI MISO
1 255 0
2 255 0
3 255 0
4 254 0
5 30 0
6 254 16
7 254 3
8 254 193

Sometimes (under high loads) the 16 reads 80, but that's probably because the 7th bit is misread (i haven't found a pattern):
16 = 0001 0000
80 = 0101 0000

But then in the 68th package it always sends:
ByteMOSIMISO
12550
22550
32550
42540
5300
6254144
72543
8254193

Same thing here, 144 sometimes becomes 280
144 = 1101 0000
208 = 1001 0000

Which i think prepares the Master that next 8-byte package will contain important stuff.
This is what comes out in package 69 with different loads:

ByteSISO 0WSO 8,5WSO 20WSO 44,5WSO 1860W
19400000
21280000
3000000
4000000
52400000
6254115116115115111
725423810231236191
82542498412321518

Which i figured out to be:
Voltage = 2*(Byte6+Byte7/255) 

Which makes sens because when it goes from Byte6=115 and Byte7>238 to Byte6=116 and Byte7=10 It implies a moderate increas in voltage (231,9V=>232,1V), but under high load, one can expect a voltage drop, and when running at 1,86 kW: Byte6=111 and Byte7=191 (223,5V) seems to be correct!

I guess Byte8 represents a very small fractions of voltage level, so i skip that one.

And the last 8-byte package hopefully gives me some sort of current measurement value so that I can calculate the power!?
Package 70 looks like this with different power loads:

ByteSISO 0WSO8,5WSO 20WSO 44,5WSO 1860W
12200000
2254001168
32542162715645
425416811431163243
52000000
6254000014
72540174090137
825425521324870

Where I have tried hard to find out what bit 2 to 4 means, please help me with that in the comment field!!!! The meter displays power factor, could it be something with that?

Anyway, I was luckey, it turned out that the last three bits sends the power value like this:
P=(Byte6*255+Byte7+Byte8/255)/2

And to get the current:
P=U*I means I=P/U  and I have all i need!!!!!

And I am one very happy engineer!

A bonus is that changing the setting to view voltage or current, doesn't change the SPI-data.


Arduino MISO sniffer

I can't have a PC next to every power plug energy meter i have hacked so next step was to program a micro controller to do the SPI-sniffing for me.

I have been using AVR's for quite some time now, but this is my first Arduino project, and for testing purposes I'll be using an Arduino Nano, but I have decided to use an 3,3 V Arduino Mini when it's time to solder everything togeather since I have a 3,3 V battery in the meter, and I am planing on transmitting the read data with either an nRF24L01+ to my rPi-setup, or the ESP8266 Wifi adapter (if it will ever arrive...). I wonder if I need a big fat cap to supply the current when sending data like the Tweetawatt!?

Anyways, my plan is to send the data to Gdrive so that i can reach it from an android app or something, but that's future work! If you read this, and now how to log data from ESP8226 to G-drive or Dropbox, I'd appreciate if you gave me some tips!

I first thought of using the built in SPI-function, but learning how to use the "bitbanging" technic on SPI sounded allot more fun! (and I'm not sure the built in SPI would work anyway without SS)

This is the psudo chode I wrote:
1. Connect GND, CLK (green cable) and SO (blue-white) to Arduino (CLKto INT0 and SO to D5) (Arduino 5V from USB for now)
2. Setup interrupt (ISR) on INT0-pin (D2) and make it trigger on rising edge (se ISR-info)
3. When trigger occures: loop as long as CLK is high while logging the time
4. When CLK goes low: check if the delay was between 1-2ms, if so then we are in clk-sync and next clk-rise will be the start of a new byte (this is the delay in between every one of the 70 packages in a transmission)
5. Let CLK-interrupt trigger 40 times to skip the first 5 bytes of the current package
6. Save status on pin 5 (MISO) every time CLK-interrupt triggers to two integers (the next 8*2 times, which will be Byte6 and 7) by using shifting bits method "<<"
7. Let clk trigger 8 more times to finish a complete package and stay in sync
8. check if Byte7!=3, If true: its the 69th package => use byte 6 and 7 to calculate U and proceed with the next step, otherwise (Byte7==3) then: set sync=false and go back to step 3 and wait/look for next package.
9. Let CLK-interrupt trigger 40 more times to skip the first 5 bytes of the 70th package
10. Save byte 6, 7 and 8 in integers by shifting bits each time a new bit is read (8*3 times).
11. Calculate P and then I=P/U
12. Send U,I,P to computer for debug.


And believe it or not, after a good couple of hours of debugging it now works like a charm!


Here is the code that now sends the data to the Arduino-IDE, but is easily changed to an nRF24L01+ and hopefully the ESP8266  as well...


/*
Reads voltage and power from China-style energy meter.
Collecting data by eavesdropping on the MOSI-line (master in slave out)
between the energy monitoring chip (ECH1560) and the main processor*/
const int CLKPin = 2; // Pin connected to CLK (D2 & INT0)
const int MISOPin = 5; // Pin connected to MISO (D5)
//All variables that is changed in the interrupt function must be volatile to make sure changes are saved.
volatile int Ba = 0; //Store MISO-byte 1
volatile int Bb = 0; //Store MISO-byte 2
volatile int Bc = 0; //Store MISO-byte 2
float U = 0; //voltage
float P = 0; //power
float ReadData[3] = {0, 0, 0}; //Array to hold mean values of [U,I,P]
volatile long CountBits = 0; //Count read bits
volatile int Antal = 0; //number of read values (to calculate mean)
volatile long ClkHighCount = 0; //Number of CLK-highs (find start of a Byte)
volatile boolean inSync = false; //as long as we ar in SPI-sync
volatile boolean NextBit = true; //A new bit is detected
void setup() {
//Setting up interrupt ISR on D2 (INT0), trigger function "CLK_ISR()" when INT0 (CLK)is rising
attachInterrupt(0, CLK_ISR, RISING);
//Set the CLK-pin (D5) to input
pinMode(CLKPin, INPUT);
//Set the MISO-pin (D5) to input
pinMode(MISOPin, INPUT);
// initialize serial communications at 9600 bps: (to computer)
Serial.begin(19200);
}
void loop() {
//do nothing until the CLK-interrupt occures and sets inSync=true
if(inSync == true){
CountBits = 0; //CLK-interrupt increments CountBits when new bit is received
while(CountBits<40){} //skip the uninteresting 5 first bytes
CountBits=0;
Ba=0;
Bb=0;
while(CountBits<24){ //Loop through the next 3 Bytes (6-8) and save byte 6 and 7 in Ba and Bb
if(NextBit == true){ //when rising edge on CLK is detected, NextBit = true in in interrupt.
if(CountBits < 9){ //first Byte/8 bits in Ba
Ba = (Ba << 1); //Shift Ba one bit to left and store MISO-value (0 or 1) (see http://arduino.cc/en/Reference/Bitshift)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Ba |= (1<<0); //changes first bit of Ba to "1"
} //doesn't need "else" because BaBb[0] is zero if not changed.
NextBit=false; //reset NextBit in wait for next CLK-interrupt
}
else if(CountBits < 17){ //bit 9-16 is byte 7, stor in Bb
Bb = Bb << 1; //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bb |= (1<<0); //changes first bit of Bb to "1"
}
NextBit=false; //reset NextBit in wait for next CLK-interrupt
}
}
}
if(Bb!=3){ //if bit Bb is not 3, we have reached the important part, U is allready in Ba and Bb and next 8 Bytes will give us the Power.
Antal += 1; //increment for mean value calculations
//Voltage = 2*(Ba+Bb/255)
U=2.0*((float)Ba+(float)Bb/255.0);
//Power:
CountBits=0;
while(CountBits<40){}//Start reading the next 8 Bytes by skipping the first 5 uninteresting ones
CountBits=0;
Ba=0;
Bb=0;
Bc=0;
while(CountBits<24){ //store byte 6, 7 and 8 in Ba and Bb & Bc.
if(NextBit == true){
if(CountBits < 9){
Ba = (Ba << 1); //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Ba |= (1<<0); //changes first bit of Ba to "1"
}
NextBit=false;
}
else if(CountBits < 17){
Bb = Bb << 1; //Shift Ba one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Ba[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bb |= (1<<0); //changes first bit of Bb to "1"
}
NextBit=false;
}
else{
Bc = Bc << 1; //Shift Bc one bit to left and store MISO-value (0 or 1)
//read MISO-pin, if high: make Bc[0] = 1
if(digitalRead(MISOPin)==HIGH){
Bc |= (1<<0); //changes first bit of Bc to "1"
}
NextBit=false;
}
}
}
//Power = (Ba*255+Bb)/2
P=((float)Ba*255+(float)Bb+(float)Bc/255.0)/2;
//Voltage mean
ReadData[0] = (U+ReadData[0]*((float)Antal-1))/(float)Antal;
//Current mean
ReadData[1] = (P/U+ReadData[1]*((float)Antal-1))/(float)Antal;
//Power mean
ReadData[2] = (P+ReadData[2]*((float)Antal-1))/(float)Antal;
//Print out results (i skipped the mean values since the actual ones are very stable)
Serial.print("U: ");
Serial.print(U,1);
Serial.println("V");
Serial.print("I: ");
Serial.print(P/U*1000,0); //I=P/U and in milli ampere
Serial.println("mA");
Serial.print("P: ");
Serial.print(P,1);
Serial.println("W");
Serial.println("");
if(Antal==10){ //every 10th 70-package = every ~10s
//transmit ReadData-array to nRF or Wifi-module here:
//transmission function here...
//Reset ReadData-array
ReadData[0] = 0;
ReadData[1] = 0;
ReadData[2] = 0;
//reset mean-value counter
Antal=0;
}
inSync=false; //reset sync variable to make sure next reading is in sync.
}
if(Bb==0){ //If Bb is not 3 or something else than 0, something is wrong!
inSync=false;
Serial.println("Nothing connected, or out of sync!");
}
}
}
//Function that triggers whenever CLK-pin is rising (goes high)
void CLK_ISR(){
//if we are trying to find the sync-time (CLK goes high for 1-2ms)
if(inSync==false){
ClkHighCount = 0;
//Register how long the ClkHigh is high to evaluate if we are at the part wher clk goes high for 1-2 ms
while(digitalRead(CLKPin)==HIGH){
ClkHighCount += 1;
delayMicroseconds(30); //can only use delayMicroseconds in an interrupt.
}
//if the Clk was high between 1 and 2 ms than, its a start of a SPI-transmission
if(ClkHighCount >= 33 && ClkHighCount <= 67){
inSync = true;
}
}
else{ //we are in sync and logging CLK-highs
//increment an integer to keep track of how many bits we have read.
CountBits += 1;
NextBit = true;
}
}
view raw EnergyMeter.ino hosted with ❤ by GitHub

Update!

I now have a working setup where the energy meter is completely wireless with an Arduino mini pro 3,3V and a nRF24L01+ module! =)
Se next post for further information.
/Kalle

Monday, August 25, 2014

Move program between terminals

Finally I have found an easy way of moving a running program from one terminal to another in Linux.

1. Install a neat program called "reptyr"
     $sudo apt-get install reptyr
2. start a never ending program in one terminal
3. start a second terminal and find the PID of the never ending program by running
     $ps -er | grep nRF  
          -where the "nRF" part is part of the never ending program name
          -you might want to make the terminal window broader to see all the text
4. look after the PID that corresponds to the ps-output:
     pi         2801     2800     1   20:57  pts/1       00:00:01 python3   /home/pi/nRF24L01p.py
          -the PID is the number 2801 in the example above.
5. in the second terminal, run:
     $reptyr 2801
and the second terminal will print out 11 rows of text starting with [+] to tell you everything worked, and at the bottom show the out and input of the program.
The first terminal will go on and ask for a new input and act as if nothing has happened.


Another useful thing with the PID is when you want to kill a process. just type $kill 2801 where 2801 is the PID