@Nca78 , updating: I figured out how to connect the load, so I'm done with it (including calibration).
I changed the original code a bit, as I also wanted it a bit more responsive. I didn't lift pin 15 as you did.
BTW, what bootloader + clock are you using? Perhaps that could influence? I'm using MYSBootloaderV13pre.hex, 8Mhz internal clock...
Changes:
- Less average reading per cycle (from 32 to 4 ) --> Didn't notice significant changes in measurements.
- More accumulated avg reads ( from 16 to 32 ) --> Just to keep a less volatile avg numbers in display.
- Change the logic of short/long press. short press (~1s) = change mode, long press (~3s) = Offset.
In case you want to give it a try...
// uA meter with HX711
/*
PROJECT: MySensors - uA meter with HX711
PROGRAMMER: AWI
DATE: 20170414/ last update:
FILE: AWI_uA_meter.ino
LICENSE: Public domain
Performance improvements: rvendrame
Hardware: tbd Nano ATmega328p board w/ NRF24l01
Special:
program with Arduino Nano
SUMMARY:
Measures mV accross a shunt resistor ~ uA - channel A
Measures mV on channel B
Modes:
- default: measure uV in full resolution (Stable reading only for 0.1uV)
- other:
A: channel A: default, amplification 128 - div 500: 0.1uV stable, range +/- 20mV, (1ohm +/- 20mA, res 100 nA)
B: channel B: amplification 32 - div 125: 100nA stable, range +/- 80mV, (10 ohm +/- 8 mA, res 10 nA)
AB: both channels:
- uA - calibration: depending on the actual shunt:
0.47 ohm -> 1 uV ~ 2uA, range -40 mA - 40 mA
1 ohm -> 1 uV = 1uA, range -20 mA - 20 mA
10 ohm -> 1 uv = 0.1uA
- mV - calibration, depend on amplification
Button switch:
- Short press, reset current channel to offset 0 (keep terminals shorted, no need with uA ;-)
- Long press, change channel A (uA) / B(uA)/ A & B (uA)
Hx711 24bit weight scale sensor
- Noise and temperature sensitive (x bit effective)
OLED 128x64 display
Remarks:
Size is large as result of font library for display
update:
*/
#include <U8g2lib.h> // U8glib for OLED display
#include <Wire.h> // I2C
#include <Button.h> // https://github.com/JChristensen/Button
#include "HX711.h" // local ADC lib
const double calibrationFactorA = 599.18f ; // calibration for channel A: set to 1.0 for known current and divide
const double calibrationFactorB = 149.76f ; // calibration for channel B: set to 1.0 for known current and divide
long offsetChannelA = 0 ; // channel offsets for A and B (drifts) are calibrated at startup and on command.
long offsetChannelB = 0 ;
const uint8_t HX711_dout = A1 ; // HX711 data out pin
const uint8_t HX711_sck = A0 ; // HX711 serial clock
const uint8_t buttonPin = A2 ; // connects the button to select function and reset offset
//const unsigned long longPress = 1500UL ; // - long press set reference temperature - in ms // - when alarm, short press resets alarm
Button myBtn(buttonPin, true, true, 40); // Declare the button( pin, pullup, invert, debounce ms)
enum convertMode_t {channelA, channelB, channelAB} ; // measurement modes, 32 port B / 128 port A / A & B
HX711 scale; // instantiate ADC
// U8G instantiate, Change this constructor to match the display!!!
U8G2_SSD1306_128X64_NONAME_1_HW_I2C u8g(U8G2_R0, /* reset=*/ U8X8_PIN_NONE); // All Boards without Reset of the Display
const int nettReadingsSize = 32 ; // the number of readings to determine the average and calculate variance/ accuracy
double lastReading, lastReadingB ;
double nettReadings[nettReadingsSize] ; // store the rolling average of readings
int nettReadingPointer = 0 ;
convertMode_t convertMode = channelA ; // default channelA
enum state_t {idleState, waitForRelease} ; // define possible states
static state_t state = idleState ;
void setup() {
Serial.begin(115200);
Serial.println("AWI uA meter");
// u8g setup
u8g.begin() ;
u8g.setFont(u8g2_font_helvR14_tf); // 'r' = reduced (or 'n' = numeric) font only for size
//u8g.setFont(u8g2_font_profont15_tf); // 'r' = reduced (or 'n' = numeric) font only for size
// HX711.DOUT - pin #A1
// HX711.PD_SCK - pin #A0
// if parameter "gain" is ommited; the default value 128 is used by the library
// 64 & 128 is port A ; 32 is port B
scale.begin(HX711_dout, HX711_sck, 128); // set port based on state of selection
LCD_banner("Initializing") ;
Serial.print("read average: \t\t");
Serial.println(scale.read_average(20)); // print the average of 20 raw readings from the ADC
getOffset(); // get the offsets (drift values)
scale.set_offset(offsetChannelA) ; // set it for measured channel
scale.set_scale(calibrationFactorA); // this value is obtained by calibrating with known value; see the README for details
Serial.print("read: \t\t");
Serial.println(scale.read()); // print a raw reading from the ADC
Serial.print("read average: \t\t");
Serial.println(scale.read_average(10)); // print the average of 20 readings from the ADC
Serial.print("get value: \t\t");
Serial.println(scale.get_value(5)); // print the average of 5 readings from the ADC minus the tare weight, set with tare()
Serial.print("get units: \t\t");
Serial.println(scale.get_units(5), 3); // print the average of 5 readings from the ADC minus tare weight, divided by scale
Serial.println("Readings:");
}
void loop() {
//Serial.print("one reading:\t");
//Serial.print(scale.get_units(), 1);
//Serial.print("\t| average:\t");
//Serial.println(scale.get_units(30), 3);
checkButton();
// get ADC readings dependent on setting: read A, B or A & B
// only A reads has average buffer when A&B mode is selected
if (convertMode == channelA){
scale.set_gain(128) ;
scale.set_offset(offsetChannelA) ;
scale.set_scale(calibrationFactorA ); // set division to A value and set mode to A
lastReading = scale.get_units(4) ; // get value (average 4 readings)corrected with scaling
nettReadings[nettReadingPointer] = lastReading ; // store readings in averagebuffer
nettReadingPointer = (++nettReadingPointer) % nettReadingsSize ; // increment and wrap
checkButton();
LCD_local_display();
} else if (convertMode == channelB){
scale.set_gain(32) ;
scale.set_offset(offsetChannelB) ;
scale.set_scale(calibrationFactorB); // set division to B value and set mode to B
lastReading = scale.get_units(4) ; // get value (average 4 readings)corrected with scaling
nettReadings[nettReadingPointer] = lastReading ; // store readings in averagebuffer
nettReadingPointer = (++nettReadingPointer) % nettReadingsSize ; // increment and wrap
checkButton();
LCD_local_display();
} else if (convertMode == channelAB){ // if both channels average 128 readings iso 32 (no buffer)
scale.set_gain(128) ;
scale.set_offset(offsetChannelA) ;
scale.set_scale(calibrationFactorA); // set division to A value and set mode to A
lastReading = scale.get_units(2) ; // get value (average 4 readings)corrected with scaling
checkButton();
scale.set_gain(32) ;
scale.set_offset(offsetChannelB) ;
scale.set_scale(calibrationFactorB); // set division to A value and set mode to A
lastReadingB = scale.get_units(2) ; // get value (average 4 readings) corrected with scaling
checkButton();
LCD_local_displayAB();
}
//scale.power_down(); // put the ADC in sleep mode
//delay(500);
//scale.power_up();
//delay(100);
}
void checkButton() {
myBtn.read(); // read button state
switch (state){
case idleState: // Idle
if (myBtn.wasPressed()) { // Pressed
// change channel and wait release
state = waitForRelease ;
}
break ;
case waitForRelease:
if (myBtn.pressedFor(3000UL)) { // Long Press
LCD_banner("Offset");
getOffset();
state = idleState;
} else if (myBtn.wasReleased()) { // Short Press
state = idleState;
switchMode() ;
}
break ;
}
}
void LCD_banner(const char *s){
/* prints all avaiable variables on LCD display with units
input: all "last" variables
*/
u8g.firstPage();
do {
int strWidth = u8g.getStrWidth(s) ; // get the length of the string to determine print position
u8g.drawStr((128- strWidth)/2, 40, s ) ; // print right aligned
} while (u8g.nextPage()) ;
}
void LCD_local_display(void){
/* prints all avaiable variables on LCD display with units
input: all "last" variables
*/
char buf[21]; // buffer for max 20 char display
char lastNettBuf[14];
dtostrf(lastReading, 10, 2, lastNettBuf); // Convert real to char
char averageNettBuf[14];
dtostrf(nettReadingsAverage(), 10, 2, averageNettBuf); // Convert real to char
char spreadNettBuf[14];
dtostrf(nettReadingsSpread(), 10, 2, spreadNettBuf); // Convert real to char
Serial.print("Average: \t") ; Serial.print(nettReadingsAverage());
Serial.print("\tSpread: \t") ; Serial.println(nettReadingsSpread());
u8g.firstPage();
do {
checkButton();
snprintf(buf, sizeof buf, "Current %s", (convertMode==channelB)?"B":"A"); // Header
int strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth)/2, 14, buf ) ; // print middle aligned
u8g.drawStr(0,31,"I") ; // Current
snprintf(buf, sizeof buf, "%10s\xB5\A", lastNettBuf);
strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth), 31, buf ) ; // print right aligned
u8g.drawStr(0,47,"avg") ; // Average current
snprintf(buf, sizeof buf, "%10s\xB5\A", averageNettBuf);
strWidth = u8g.getStrWidth(buf) ; // get the length of the string to determine print position
u8g.drawStr((128- strWidth), 47, buf ) ; // print right aligned
u8g.drawStr(0,63,"d\xB1") ; // delta +/-
snprintf(buf, sizeof buf, "%10s\xB5\A", spreadNettBuf);
strWidth = u8g.getStrWidth(buf) ; // get the length of the string to determine print position
u8g.drawStr((128- strWidth), 63, buf ) ; // print right aligned
} while (u8g.nextPage()) ;
}
void LCD_local_displayAB(void){
/* prints A & B channel on LCD display with units
input: all "last" variables
*/
char buf[21]; // buffer for max 20 char display
char lastNettBuf[14];
dtostrf(lastReading, 10, 2, lastNettBuf); // Convert real to char
char lastNettBufB[14];
dtostrf(lastReadingB, 10, 2, lastNettBufB); // Convert real to char
char lastNettBufAB[14];
dtostrf(lastReading +lastReadingB, 10, 2, lastNettBufAB); // Convert real to char for added values
u8g.firstPage();
do {
checkButton();
snprintf(buf, sizeof buf, "Current A+B"); // Header
int strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth)/2, 14, buf ) ; // print middle aligned
u8g.drawStr(0,31,"IA"); // Current A
snprintf(buf, sizeof buf, "%10s\xB5\A", lastNettBuf);
strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth), 31, buf ) ; // print right aligned
u8g.drawStr(0,47,"IB"); // Current B
snprintf(buf, sizeof buf, "%10s\xB5\A", lastNettBufB);
strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth), 47, buf ) ; // print right aligned
u8g.drawStr(0,63,"A+B"); // Current A + B
snprintf(buf, sizeof buf, "%10s\xB5\A", lastNettBufAB);
strWidth = u8g.getStrWidth(buf) ; // length of the string to determine print position
u8g.drawStr((128- strWidth), 63, buf ) ; // print right aligned
} while (u8g.nextPage()) ;
}
// calculate average of nett readings
double nettReadingsAverage() {
double sum = 0;
for (byte i = 0; i < nettReadingsSize; i++) {
sum += nettReadings[ i ];
}
return sum / nettReadingsSize;
}
// calculate spread of nett readings (+/-)
double nettReadingsSpread() {
double minReading = nettReadings[0];
double maxReading = minReading ;
for (byte i = 1; i < nettReadingsSize; i++) {
checkButton();
if (minReading > nettReadings[ i ]){
minReading = nettReadings[i] ;
}
if (maxReading < nettReadings[ i ]){
maxReading = nettReadings[i] ;
}
}
return (maxReading - minReading)/2 ;
}
// switch the mode
void switchMode(){
if (convertMode == channelA){
convertMode = channelB ;
} else if (convertMode == channelB){
convertMode = channelAB ;
} else {
convertMode = channelA ;
}
}
// assuming both channels are shorted, calculate the offset values for channel A and B
double getOffset(){
scale.set_gain(128) ; // get channel A
offsetChannelA = scale.read_average(32) ; // average 512 readings for offset
Serial.print("Offset A: \t") ;
Serial.println(offsetChannelA);
scale.set_gain(32) ; // get channel B
offsetChannelB = scale.read_average(32) ; // average 512 readings for offset
Serial.print("Offset B: \t") ;
Serial.println(offsetChannelB);
}```
