I2C with Magnetometer HMC5883L

[ilpaso 0]

Hi,

I'm new with Energia but not with Arduino.

I'm not able to communicate with HMC5883L throw I2C. The board is launchpad with msp430g2553 microcontroller.

 

I read some threads about this issue but I didn't find a solution.

#include <Wire.h>#define address 0x1E //0011110b, I2C 7bit address of HMC5883void setup(){  Serial.begin(9600);  // start serial for output  Wire.begin();        // join i2c bus (address optional for master)  //Put the HMC5883 IC into the correct operating mode  Wire.beginTransmission(address); //open communication with HMC5883  //Write CRA (00) 

[Rei Vilo 695]

Please find hint and answers that may help you at

• Need help using Energia's I2C library http://forum.43oh.com/topic/3941-need-help-using-energias-i2c-library/
• I2C internal pull-up resistors http://forum.43oh.com/topic/3451-i2c-internal-pull-up-resistors/
• I2C issues  http://forum.43oh.com/topic/3154-i2c-issues/
• Problem with I2C RTC DS1307 Module http://forum.43oh.com/topic/3872-problem-with-i2c-rtc-ds1307-module/

[ilpaso 0]

Hi Rei Vilo,

 

thank you for your reply!

I've already read these threads.

These are my feedbacks.

1) With external pull-up (10K) resistors it doesn't work.

2) I changed the twi.c file and it doesn't work.

 

It's strange because each of these threads has a different solution.

 

Regards

 

ilpaso

[Rei Vilo 695]

Does it works with Arduino?

 

Do you have a logic analyser to trace the signals?

 

I've experienced issues with some I2C devices due to weak signal when using the 3.3V MSP430G2553. Using a lower than 10k? could improve signal.

 

HMC5883L specification sheet mentions 2.2k? pull-up resistors.

[ilpaso 0]

Hi Rei Vilo,

Now it works with 4.7K pull-up risistors and the arduino sketch provided by Sparkfun (https://www.sparkfun.com/products/10530).

It also works with your library "software I2C" in pins P2_3 and P2_4.

 

I've only a problem: The magnetometer sends 6 bytes and this is the code:

 Wire.requestFrom(address, 6);
  if(6<=Wire.available()){
    x = Wire.receive()<<8; //X msb
    x |= Wire.receive(); //X lsb
    z = Wire.receive()<<8; //Z msb
    z |= Wire.receive(); //Z lsb
    y = Wire.receive()<<8; //Y msb
    y |= Wire.receive(); //Y lsb
  }

If I use the I2C software library it loses the last byte ("Y lsb").

If I change the first line of this code to "Wire.requestFrom(address, 7);" it works.

Maybe is there a little bug in the library?

 

Thank you

 

ilpaso

[Rei Vilo 695]

Thank you for pointing the bug.

 

In the function uint8_t SoftwareWire::requestFrom(uint8_t address, uint8_t length)

for (uint8_t i=0; i<length-1; i++) rxBuffer[i] = readI2C(false);

should be

for (uint8_t i=0; i<length; i++) rxBuffer[i] = readI2C(false);

As an alternative, you can use size_t SoftwareWire::write(const uint8_t *data, size_t length)

[ilpaso 0]

Thank you very much for your fantastic work!

I would like to contribute more but I need more experience.  :!!!:

 

 

bye

 

 

ilpaso