I2C with Arduino

[codetheweb]

I’m having some trouble communicating with the Arduino over I2C.

We’re planning to use it for LED strips, since almost all our PWM slots are taken. But most examples I find online use Java, not Python. Is there any way to easily write a string over I2C? For example, writing something like “rgb,10,0,255” would turn on the RGB strip.

[virtuald]

@codetheweb

I’m having some trouble communicating with the Arduino over I2C.

We’re planning to use it for LED strips, since almost all our PWM slots are taken. But most examples I find online use Java, not Python. Is there any way to easily write a string over I2C? For example, writing something like “rgb,10,0,255” would turn on the RGB strip.

Can you post a link to java code that you think will solve your problem?

[codetheweb]

Here.

@Rakusan2

My team got the Arduino communicating with the roborio over I2C using the following code on the roborio

static I2C Wire = new I2C(Port.kOnboard, 4);

if (Global.driver.Buttons.Back.changedDown) {
	String WriteString = "go";
	char] CharArray = WriteString.toCharArray();
	byte] WriteData = new byte[CharArray.length];
	for (int i = 0; i < CharArray.length; i++) {
		WriteData* = (byte) CharArray*;
	}
	Wire.transaction(WriteData, WriteData.length, null, 0);
}

And this code on the Arduino

#include <Wire.h>

void setup()
{
  pinMode (13, OUTPUT);
  Wire.begin(4);                // join i2c bus with address #4
  Wire.onReceive(receiveEvent); // register event
}

void loop()
{
  delay(100);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
  String LED = "";
 
  while ( Wire.available() > 0 )
  {
    char n=(char)Wire.read();
    if(((int)n)>((int)(' ')))
   LED += n; 
  }
  
  if (LED == "go") 
  {
    
    digitalWrite (13, HIGH);
  
    
  }
}

**

[virtuald]

First part, should be pretty straightforward.

wire = wpilib.I2C(wpilib.I2C.Port.kOnBoard, 4)

Second part– I admit the docs aren’t super clear here, but it wants you to pass it a list of things that can be converted to bytes… so either integers or a bytestring.

wire.transaction(b'go', 0)

I’m pretty sure that’ll work.

It’s weird that the java code isn’t trying to receive any data (maybe writeBulk is more appropriate?).

[codetheweb]

Thanks, works great! In case anyone else stumbles across this, here’s the code I used:

import wpilib

class MyRobot(wpilib.IterativeRobot):

    def robotInit(self):
        self.stick = wpilib.Joystick(0)
        self.arduino = wpilib.I2C(wpilib.I2C.Port.kOnboard, 4)

    def teleopPeriodic(self):
        if (self.stick.getTrigger()):
            try:
                data = self.arduino.transaction(b'go', 0)
            except:
                pass
        else:
            try:
                data = self.arduino.transaction(b'stop', 0)
            except:
                pass

if __name__ == "__main__":
    wpilib.run(MyRobot)

And

#include <Wire.h>

void setup()
{
  Wire.begin(4);                // join i2c bus with address #4
  Wire.onReceive(receiveEvent); // register event
  Serial.begin(9600);
  Serial.print("Hello");

}

void loop()
{
  delay(100);
}

void receiveEvent(int howMany)
{
  String rxString = "";
 
  while ( Wire.available() > 0 )
  {
    char n=(char)Wire.read();
    if(((int)n)>((int)(' ')))
    rxString += n; 
  }

  Serial.print(rxString);
}

[virtuald]

Awesome, I like how much shorter it is than the Java version: