RS485 example for stm32 G4

[abhijith_raj]

Hi,
Is there any RS485 example code available for STM32G497 ?
I referred in community for sample code for enabling RS485, didn't get it.

[Saket_Om]

Hello @abhijith_raj 

Unfortunately, there is no example RS485 in our STM32Cube firmware.

[abhijith_raj]

Hi @Saket_Om 
I'm implementing RS485 using USART1 and need to configure the DE (Driver Enable) pin. I came across the HAL_RS485Ex_Init() API in the HAL driver, but I didn't find any specific configuration related to the DE pin within it. Should I call HAL_RS485Ex_Init() instead of HAL_UART_Init() for RS485 functionality, or is it required to use both? Also, how exactly should the DE pin be configured in this context?

[Guenael Cadier]

Hi @abhijith_raj 

In order to use USART1 in RS485 mode, you have to call HAL_RS485Ex_Init() API (instead of HAL_UART_Init()).
You also need to configure your DE pin as Alternate Function (in addition to TX/RX pins).

You could also use STM32CubeMX, which will generate initalisation code for your project, if you prefer :

Then you should be able to find generated code in main.c and stm32g4xx_hal_msp.c files.

Regards

 

[abhijith_raj]

Hi @Guenael Cadier ,
In this configuration, the PA12 pin is used for DE control. However, in our schematics, this pin is assigned for a different purpose, so we’ve selected another GPIO for DE. How can I control the DE line in this case? Can I use HAL_GPIO_WritePin to manually control the GPIO for each transaction?

[Guenael Cadier]

Hi @abhijith_raj 

If you can't assign a pin for USART1_DE as Alternate function, then it means it cannot be driven automatically by USART1 peripheral. then, I think it should be feasible to initilialize USART1 in classic Asynchronous mode (HAL_UART_Init()) and drive your DE pin manually in your application using HAL_GPIO_xxx APIs.
Regards