I2C Busy flag problem

Posted on June 21, 2012 at 14:14

I assume you have the STM32 as master, and connect some peripheral slaves?

In this configuration we had the problem, that it can happen from time to time, that one of the slaves keeps the SDA line low. This is a blocking situation, as then the STM32 will keep the BUSY set and does not continue. In this case, you have to give out 8 SCL clock cycles ''manually'' (directly setting the SCL port pin high/low - this does NOT work via some IIC interface command...).

Best you insert some timeout checking, and if timeout happens, you should reset IIC and do these 8 SCL ''manual'' cycles.

Posted on June 21, 2012 at 15:34

thanks, it's an hardware problem, because i observe these different behaviours.

1)  if i connect an oscilloscope to GPIOB pins 8 and pin9 (SCL and SDA) everything is blocked in debugging phase, if now i disconnect both pins and reconnect only the pin 9, the program goes on (i think because a START condition is simulated).

2) if nothing is connected to the board, the debug works correctly, but (normally)  it stops after waiting for an EV6 event (I2C_EVENT_MASTER_BYTE_TRANSMITTED).