STM32 I2C arbitration lost problem

sukrubahadirarslan · ‎2013-12-23

Posted on December 23, 2013 at 23:44

hello forum.

I am trying to communicate with mpu6050 with I2C. I am trying to receive data from sensor.

But when I send second address of sensor , arbitration lost is occur. ARLO(arbitration lost bit) is set. There is one master and one slave in communication so how can ARLO bit is set ? I cant understand this situation . Can you help me pls ?

thank you.

here is my code :

uint8_t I2C_SingleByteRead(uint8_t register_address)

{

uint8_t mask=0;

while(I2C_GetFlagStatus(I2C1,I2C_FLAG_BUSY)==SET);

I2C_GenerateSTART(I2C1,ENABLE);

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_MODE_SELECT)==ERROR);

I2C_Send7bitAddress(I2C1,MPU6050_Default_Address,I2C_Direction_Transmitter);

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED)==ERROR);

I2C_Cmd(I2C1,ENABLE);

I2C_SendData(I2C1,register_address);

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_BYTE_TRANSMITTED)==ERROR);

I2C_GenerateSTART(I2C1,ENABLE);

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_MODE_SELECT)==ERROR);

I2C_Send7bitAddress(I2C1,MPU6050_Default_Address,I2C_Direction_Receiver);

********************* arbitration lost bit is set*******************

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_RECEIVER_MODE_SELECTED)==ERROR);

I2C_AcknowledgeConfig(I2C1,DISABLE);

I2C_GenerateSTOP(I2C1,ENABLE);

while(I2C_CheckEvent(I2C1,I2C_EVENT_MASTER_BYTE_RECEIVED)==ERROR);

mask=I2C_ReceiveData(I2C1);

I2C_AcknowledgeConfig(I2C1,ENABLE);

return mask;

}

chen · ‎2013-12-24

Posted on December 24, 2013 at 09:54

Hi

Do you have an oscilloscope?

Look at what is happening with the oscilloscope.

Despite what you might think - the I2C bus master is not in full control of the bus.

Any device can pull either SDA or SCL low at any time - hence the arbitration lost.

Chances are it is not your code but a real arbitration lost.

The tricky bit is understanding why.