STM32 UART Communication with DWIN LCD

AliHassan · ‎2024-12-30

Hello Everyone,
I’m working on a project where I’m interfacing a DWIN LCD with my STM32 microcontroller using UART. The UART TX and RX lines from the STM32 are connected to the RX and TX lines of the DWIN LCD, respectively. I’ve ensured that the baud rate, parity, stop bits, and other UART parameters are correctly configured on both devices. However, I’ve run into an issue: when both the TX and RX lines are connected, the LCD seems to receive dummy or incorrect values. Interestingly, if I disconnect the TX line and only leave the RX line connected, the LCD receives the correct data without any problems.
Any insights or suggestions on what might be causing this problem and how I can resolve it would be greatly appreciated. Thank you in advance for your help!
Let me know if you need further adjustments!

Mike_ST · ‎2025-01-08

Hello,

Which STM32 ?

Which LCD ?

>> The UART TX and RX lines from the STM32 are connected to the RX and TX lines of the DWIN LCD

Is GND connected ?

Andrew Neil · ‎2025-01-10

Have you monitored the TX & RX lines to see what's actually happening on the wires?

Some tips on debugging serial comms:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/tac-p/706966/highlight/true#M49

AliHassan · ‎2025-01-20

the problem was solved, the issue was in stm32 controller, as i was using stm32l432 and DWIN lcd, the stm32l432 doesn't receive and transmit data simultaneously but when i removed solder bridge on the stm32 board it worked fine.

Andrew Neil · ‎2025-01-21

@AliHassan wrote:
the issue was in stm32 controller

Your description of the fix doesn't support that conclusion:

@AliHassan wrote:
the stm32l432 doesn't receive and transmit data simultaneously .

Yes, it does - it is full-duplex.

@AliHassan wrote:
but when i removed solder bridge on the stm32 board it worked fine.

So that's an issues with the configuration of the board - not with the STM32 controller!

For the benefit of future readers, who may find this looking to solve a similar problem, please say

what board you were using, and
what solder bridge you removed.

Then please mark that as the solution:

https://community.st.com/t5/community-guidelines/help-others-to-solve-their-issues/ta-p/575256

At a guess, I suspect that you had the UART still connected to the onboard ST-Link's VCP - and that's what was interfering with your comms:

https://community.st.com/t5/stm32-mcus-boards-and-hardware/i-cannot-receive-data-while-using-usb-to-uart-for-nucleo-f411re/m-p/690201/highlight/true#M19855

https://community.st.com/t5/stm32-mcus-wireless/use-the-same-uart-with-stlink-and-with-another-module/m-p/645234/highlight/true#M18096