Nucleo H7S3L8 and RS485 (hardware flow control)

[PhilMaz]

Good morning, 

I'm writing to ask about the missing "Hardware flow control" option on our new H7S3L8 board..
We are trying to migrate a project from an F756ZG which did almost everything well (aside from the debugger). 

However, we're having an issue with our RS485 connections, which require a "DE" (driver enabled) signal :

Here's the F7 UART7 configuration (with the Hardware Flow Control option)

We tried to implement it ourselves, thinking it would just require an extra GPIO output and the following logic :

HAL_GPIO_WritePin(TX_EN_GPIO_Port, TX_EN_Pin, GPIO_PIN_SET);
HAL_UART_Transmit(&huart7, data, strlen (data) , 1000);
HAL_GPIO_WritePin(TX_EN_GPIO_Port, TX_EN_Pin, GPIO_PIN_RESET);

But right now we're having issues communicating with our sensors (we're going through a MOD-RS485 board)

Does anyone know if the H7S3L8 will eventually get the feature, is it something that can easily be done manually... or should we give up and move to a different H7 variant? (like the H723ZG)

Thank you very much!
Philippe Mazouer

[STTwo-32 · Accepted solution]

Hello @PhilMaz 

I confirm that issue on CubeMX. The Feature to enable directly the Hardware flow control (RS485) (as on the F7 or other MCUs that support this feature) is not implemented. I've escalated this internally for Correction on the Coming releases of CubeMX (under internal ticket number 189949). For Now, you have to do it manually as mentioned on the paragraphs 53.5.21 and 54.4.14 of the RM0477. Don't forget, the Driver enable (DE) share the same AF number and the same pin as the Request to send pin (RTS). 

Best Regards.

STTwo-32

[PhilMaz]

Thank you so much for the update!

We'll eagerly await an update of CubeMX then.
Philippe