four uarts on stm32L433?

[John Griswold]

Posted on September 05, 2017 at 22:05

Is it possible to get four USART/UART devices at once on the STM32L433 in a 64-pin package? I need one UART for input, one for output, one for external logging, and USART1 for debugging.

Is this doable? I've used CubeMX to try various configurations, and I end up short of the goal. I'll also need an ADC and a PWM or DAC, and DMA on at least the input device would be nice.

Suggestions?

[Tesla DeLorean]

Posted on September 05, 2017 at 22:26

Do they have different baud rates?

Could you use the other half of the 'Input USART' for the debugger/telemetry output?

Suggest you pull the Data Sheet 

and a highlighter pen

, print out the pin list and go over the 64-pin column down, and the across the USART lines.

[John Griswold]

Posted on September 05, 2017 at 22:51

Not that simple. The 'input' side also sends commands. All ports run at the same baud rate (921600 - yeah, I know!)

CubeMX shows that all of the pins are not conflicting, but I can only get one to work, apparently, in the mode where I have four UARTs going. Test case is pretty simple - I print a test string to each port at main() after initialization, then target one UART for input/output, and send characters to the L433 using TeraTerm. I can see the printed string, but not the keyed-in data, leading me to think that the input channels aren't working properly on all UARTs.

Kind of baffling.

[Tesla DeLorean]

Posted on September 06, 2017 at 03:30

If the pins map then it should work, whether CubeMX/HAL screws up from there who knows.

Make a simple loop, polling the RXNE from each (LP)U(S)ART and echoing back the data.

while(1)

{

  uint16_t data;

  if (USARTX->ISR & USART_ISR_RXNE) // Data Pending

  {

   data = USARTX->RDR & 0xFF;

   if (USARTX->ISR & USART_ISR_TXE) // should be empty (balanced?)

     USARTX->TDR = data; // Echo back

  }

  // repeat for all UART/USART/LPUART

  // ....

}