Adapt I2C Arduino code for particle Photon (for a moisture sensor)

Troubleshooting
1

Hi all,

I’m tying to adapt this arduino code for a particle photon but I get wrong values from my sensor (see below). I tried the arduino code and it works well with my uno.

Any ideas?

Thanks a lot !

#include <Wire.h>

void writeI2CRegister8bit(int addr, int value) {
  Wire.beginTransmission(addr);
  Wire.write(value);
  Wire.endTransmission();
}

unsigned int readI2CRegister16bit(int addr, int reg) {
  Wire.beginTransmission(addr);
  Wire.write(reg);
  Wire.endTransmission();
  delay(20);
  Wire.requestFrom(addr, 2);
  unsigned int t = Wire.read() << 8;
  t = t | Wire.read();
  return t;
}

void setup() {
  Wire.begin();
  Serial.begin(9600);
  writeI2CRegister8bit(0x20, 6); //reset
}

void loop() {
  Serial.print(readI2CRegister16bit(0x20, 0)); //read capacitance register
  Serial.print(", ");
  Serial.print(readI2CRegister16bit(0x20, 5)); //temperature register
  Serial.print(", ");
  writeI2CRegister8bit(0x20, 3); //request light measurement 
  Serial.println(readI2CRegister16bit(0x20, 4)); //read light register
}

Here is my Particle code:

#include "application.h"

void writeI2CRegister8bit(int addr, int value) {
  Wire.beginTransmission(addr);
  Wire.write(value);
  Wire.endTransmission();
}

unsigned int readI2CRegister16bit(int addr, int reg) {
  Wire.beginTransmission(addr);
  Wire.write(reg);
  Wire.endTransmission();
  delay(20);
  Wire.requestFrom(addr, 2);
  unsigned int t = Wire.read() << 8;
  t = t | Wire.read();
  return t;
}

void setup() {
  Wire.begin();
  Serial.begin(9600);
  writeI2CRegister8bit(0x20, 6); //reset
}

void loop() {
  Particle.publish("test", String(readI2CRegister16bit(0x20, 0))); //read capacitance register
  Particle.publish("test", String(readI2CRegister16bit(0x20, 5))); //temperature register
  writeI2CRegister8bit(0x20, 3); //request light measurement 
  Particle.publish("test", String(readI2CRegister16bit(0x20, 4))); //read light register
}

The data i get from all the particile.publish:
{“data”:“4294967295”,“ttl”:“60”,“published_at”:“2016-02-01T20:04:17.514Z”,“coreid”:“210025001047343339383037”,“name”:“test”}

2

arduino to photon i2c should be about the same , but one thing I’ve noticed is you don’t have a delay in your loop and using Particle.publish which as a limit of 1 per second.

3

One other thing to note: on a typical Arduino, unsigned int is a 16-bit type but on Photon it is a 32-bit type. Although I don’t see how that would hurt you here, I would use a more specific type in the Photon code, with uint16_t being the best choice.

As @peter_a stated above, you are likely going over the publish limit, in which case you just won’t get your events.

4

Thanks for your answers, I added a delay and it turns out that I forgot the pull-up resistors :sweat: (It worked without it with an arduino uno)

1 Like
5

Sorry writeing in a old post but do you have your latest working code you can show Jibsgrl?

6

IMHO (after actually reading the thread) it seems the code runs as is (plus one extra line delay(5000); at the end of loop() and the required pull-up resistors.

BTW:

Actually on the Uno it doesn't work without them, but the Uno has them on board.