STM32F4 + UART + DMA + IDLE detection + High Rates + Variable Length Messages = CHAOS!

[#1]

Hi!

I have an INS that sends the following frames:

• Frame 1 of 60 bytes every 40 ms
• Frame 2 of 70 bytes every 20 ms
• Frame 3 of 32 bytes every 1s
• Frame 4 (unwanted, but impossible to deactivate) of almost 500 bytes every 2s.

I am implementing receive with Normal DMA, 115200 baudrate and IDLE detection, but I have the following problems:

1) The frames I do want are smaller than 100 bytes, but if I declare the receive buffer that size, the reception stops.

2) For that reason I have declared the buffer with a size of 500.

3) As the buffer length is 500, when the callback (TC, I ignore HT) is executed, I observe the content and there are mixed frames. I would expect that whenever IDLE is detected it will hit the callback and write to buffer position 0, but I don't know what's going on.

4) I lose frame 3, which is the smallest and least frequent.

Any suggestion?

Thanks a lot!

[Bob S]

Are you providing a HAR_UARTEx_RxEventCallback() function? That function is what gets called when an IDLE event is detected. If you instead only look for the DMA HT and TC callbacks, that ignores idle breaks.

[#3]

Yes, that is my callback function. And inside it I make a copy of the buffer because the reception happens very fast.

[Tesla DeLorean]

Generally the point of have the HT interrupt is to allow for you to empty the inactive half of a ping-pong buffer.

I'm not sure 115200 would overwhelming for a interrupt based solution, but one could certainly construct a circular DMA buffer, and attend to it periodical. Not sure I'd be using the HAL for any of that, as it has trouble keeping out of it's own way.

[#5]

I am precisely using HAL :(

Okay, I'll try with circular buffer for DMA. Thanks