Is it possible to use the system bootloader via UART as half duplex (RS485)?

[AGhez]

I have a STM32H7 connected to a STM32L1 via RS485. I would like to use the H7 to reprogram the L1 using the system bootloader.

Has the USART to be full duplex?

Thank you, regards

[Peter BENSCH]

The system bootloader uses both lines, RX and TX for the USART, thus works full-duplex.

Details can be found in AN3155: USART protocol used in the STM32 bootloader.

Hope that helps?

Regards

/Peter

[AGhez]

Hi Peter,

thank you for your quick reply!

We are using a MAX22025 (Half-Duplex RS-485/RS-422 Transceivers with AutoDirection Control), so we are able to use both USART pins, but we will not able to use them at the same time.

Is there any situation where there is the need of a simultaneously communication? Or where it is not know if the system bootloader is going to send something..?

Thank you,

regards

[Peter BENSCH · Accepted solution]

I was a bit too quick with the previous answer: it may well be that the bootloader also communicates half-duplex via USART. The easiest way to check this is to test the various functions of the bootloader (connecting, flashing, reading, deleting, etc) with your setup, i.e. via USART, but with STM32CubeProgrammer.

Regards

/Peter