Trying to understand why USART is not working properly on high baud rates

[Khetag Goiaev]

While USART (receive from PC and transfer of gained information back, pic. 1) perfectly works on low baud rates like 9600, use of high baud rates leads to obscure results (bad receive and OK transmit, pic. 2)

STM32L476VGT6

[Khetag Goiaev]

In the picture I show:

1 line - STM32 TX/PC RX

2 line - STM32 RX/PC TX

[Khetag Goiaev]

Anyway, example of echoing "1234567890" on speeds (same scheme for lines):

• 9600 b/s
• 56000 b/s

[waclawek.jan]

Even your LA does not receive the data properly, why do you think this is problem in STM32?

Check your ground connections. Try using a different UART/USB transceiver.

JW

[TDK]

The STM32 TX looks perfect. The PC TX isn't a valid UART signal at any baud rate, but that's not the fault of the STM32.

[Javier1]

I see you got a nice logic analyzer, what if you use also an oscilloscope? ¿did you ruled out noise in the data lines already?

[S.Ma]

I don't understand, 115200bps is typical baudrate for many applications, maybe because long ago the 2 wire I2C bus was 100kbps. I can make rs232 with HC05 module at 115200bps using HSI internal clock. No sweat bringup. It seems the issue is something like something obvious and overlooked.