STM32F100: UART1 and I2C2 simultaneously

[xobs]

Hi,

I'm trying to use both UARTD1 and I2C2 on an STM32F101 (similar to an STM32F100). I have my board defined, and I'm getting debug text out the serial port. The serial port will be the primary means of communication with this device.

I noticed that when I initialize I2C2 before UARTD1, I'm able to see text on the serial port but I only get the I2C address emitted on the I2C bus. Weirdly, it looks like the I2C data is ending up on the serial port rather than getting sent.

If I initialize UARTD1 before I2C2, then I2C2 is able to send data but I get no serial text at all.

In my mcuconf.h I have I2C2 on DMA priority 3, and USART1 at priority 0.

I did notice that both UARTD1 and I2C2 are defined to have their TX and RX DMA stream IDs set as STM32_DMA_STREAM_ID(1,4) and STM32_DMA_STREAM_ID(1,5) respectively, but I'm not sure how to change that.

How can I use both UARTD1 and I2C2 at the same time?

[xobs]

Answering my own reply. According to the reference manual, both devices share DMA channels 4 and 5. So the answer is: You don't use DMA.

So my options are either to use PIO or redesign the board.

[Giovanni]

You have two more options:

1) Use the Serial driver instead of the UART driver (SD1) which does not require a DMA.
2) Continue to use UARTD1 and I2CD2 but not at the same time (when one is started the other must be stopped, the DMAs are reallocated automatically on the fly).

Giovanni