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I'm working on transceiving data on stm32F04xx. When I transmit data from the MCU at lower speed, it looks like if the baudrate was wrong and I get a bunch of question marks. When I increate transmission speed. I can read the data I'm sending. I've used to stm32cubeIDE to generate a simple UART code and only added

HAL_UART_Transmit(&huart2, "test\r\n", sizeof("test\r\n"), 1000);
HAL_Delay(500);

in the while loop.

On my NUCLEO-F042K6 evaluation board, I don't see any issues printing data on the tty port. But I have another device which uses the same stm32f042xx chip that only works when transmitting UART data at higher speed. so when i change my delay to something like 80 milliseconds, I can read the data flow.

I've attempted to flash the same binary that I flashed on my evaluation board on the other MCU I have but again the data only readable at higher transmission speed.

I'm flashing the MCU with stm32flash tool so I don't know if that can make a difference where on the eval board, I'm using the stm32cubeIDE to flash it.

I'm not sure what's going on here, I've tried different baudrates and different clock configurations and that doesn't seem to help too.

What could possibly cause the data to be unreadable like if the baudrate was wrong when transmitting at low speed?

Ahmed Jalal
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  • Is HAL_UART_Transmit a blocking function? – Ilya Jun 10 '22 at 14:02
  • @Ilya id doesn’t really matter, I’ve tried transmit dma and still didn’t work. I get a bunch of question marks when at low speed transmission. – Ahmed Jalal Jun 11 '22 at 02:30
  • But if you don't do delay and jump right to the next part of code, whatever it is, it sends everything ok? – Ilya Jun 11 '22 at 06:14
  • @Ilya as long as i'm transmitting faster than 80ms between each message, the messalge looks ok. when i send at 100ms per message it starts to show question marks meaning the baudrate is wrong – Ahmed Jalal Jun 13 '22 at 05:37

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