Returned data is incorrect

[jbaldwinroberts]

Hi,

Thanks for this.

Im trying to get communications working between a raspberry pi and an mBed.

My raspberry pi code is:

var i2c = require('i2c');
var address = 0x08;
var wire = new i2c(address, {debug:false, device:'/dev/i2c-1'});

wire.readBytes(49, 10, function(err, res) {
    // result contains a buffer of bytes
    var counter = 0;
    for (counter=0; counter<res.length; counter++)
    console.log(res[counter] + "\r\n");
});

My mBed code is:

 #include <mbed.h>

 I2CSlave slave(p9, p10);

 int main() {
     char buf[10];
     char msg[] = "1234567890";

     slave.address(0x10);
     while (1) {
         int i = slave.receive();
         switch (i) {
             case I2CSlave::ReadAddressed:
                 slave.write(msg, strlen(msg) + 1); // Includes null char
                 printf("Read Addressed: %s\n\r", msg);
                 break;
             case I2CSlave::WriteGeneral:
                 slave.read(buf, 10);
                 printf("Read G: %s\n", buf);
                 break;
             case I2CSlave::WriteAddressed:
                 slave.read(buf, 10);
                 printf("Write Addressed: %s\n\r", buf);
                 break;
         }
         for(int i = 0; i < 10; i++) buf[i] = 0;    // Clear buffer
     }
}

For some reason my mBed shows on my raspberry pi as 0x08 even though its address is set to 0x10, although i dont think this matters?

When i run the raspberry pi code my mBed outputs:

Write Addressed: 1 // This is equal to 49 converted to ASCII Read Addressed: 1234567890

and my raspberry pi outputs:

test 60 23 0 0 164 163 148 190 172 23

These numbers don't match what I'm sending and don't change when i change what I'm sending.

Any ideas?

Thanks

Joe

[kelly]

Do you have pull-up resistors on the SDA and SCL?

[jbaldwinroberts]

I have tried both with and without and i get the same result. I don't think their needed as the pi has internal pull ups on the I2C lines.

Sending data works, just not receiving

Thanks

[kelly]

hmm, I'm not sure what's wrong. If I had an mbed device, i'd test it out, but a little difficult without one. I've had success reading from an Arduino and other devices.

Does anything change if you use readByte?

[jbaldwinroberts]

I have an Arduino, would you be able to post the code you tested it with and i'll see if it works. Thanks

[jbaldwinroberts]

Hi, so i tried readByte and it does not get into the callback, have I done something wrong?

var i2c = require('i2c');
var address = 0x08;
var wire = new i2c(address, {debug:false, device:'/dev/i2c-1'});

wire.readByte(function(err, res) {
console.log(res);
console.log("test");
});

Also my mBed is getting read twice when i run the above code not once?

Thanks

[kelly]

Here is a really basic example:

#include "Wire.h"

byte data[3] = {1, 2, 3};

void requestEvent()
{
  Serial.println('requested');
  Wire.write(data, 3);
}

void setup() {
Serial.begin(115200);
Wire.begin(4);
Wire.onRequest(requestEvent);  // register event
}

void loop() {
  delay(100);
}

Wire = require('i2c');

wire = new Wire(0x04, {
  device: '/dev/i2c-0'
});

//0x00 cmd isn't used, but required
wire.readBytes(0x00, 3, function(err, res) {
  return console.log(res);
});

[ajitam]

Hi, I'm having some problem with wire.readByteS to. wire.readByte works on but wire.readByteS never triggers requestEvent.

Any ideas?