Using Lilypad as I2c Slave for GSM module TC65

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I try to build a small sensor interface to connect to a GSM module. The TC65 has an external I2C interface. I connected my LilyPad to the I2C connector of the TC65 and encounter some strange responses from the LilyPad.

To verify that my programming does not cause the problem I bought a I2C temperature sensor and connected it to the TC65. The sensor delivers 6 byte of data on a read request. I tested the Sensor with the TC65 and got:

37 8F 39 72 37 8F

After this I implemented a small program that should send the same bytes from the LilyPad to the TC65:

#include <Wire.h>

#define LED_PIN         13
#define SENSOR_ADDRESS 120


byte data[6] = {0x37, 0x8F, 0x39, 0x72, 0x37, 0x8F};
boolean requestPending=false;    
    
void setup() {
  // Small Light show to be sure the software is running
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, HIGH);
  delay(1000);
  digitalWrite(LED_PIN, LOW);
  delay(100);
  digitalWrite(LED_PIN, HIGH);
  delay(1000);
  digitalWrite(LED_PIN, LOW);
  Wire.begin(SENSOR_ADDRESS);
  Wire.onRequest(requestEvent);
}


void loop() {
  delay(100);
}


void requestEvent(){
    Wire.send(data, 6);
}

I started the request with 100kbps I2C baudrate and got:
37 63

I adjusted the baudrate to 400kbps (on the TC65) and got:
37 0F 8F F0 39 00 72 00 37 0F

The black numbers are my data and the red numbers are ... ?

Maybe someone can answer the questions I have.

I thought the default i2c baudrate on the LilyPad is 100kbps is this right ?

Does anyone has an idea what could cause such a problem ? (common GND and PullUps are installed)

Any tips on what to test or to do to investigate the problem ?

Thanks in advance !

Ciao
Matsimoto