/* Enable receiver during sending, required for i.MX devices */
rs485conf.flags |= SER_RS485_RX_DURING_TX;
(or rs485-rx-during-tx; in the device tree)
Why would this property be mandatory for i.MX devices, regarding the comment above? I guess it actually depends on the PCB routing? (e.g. RX_EN and TX_EN both controlled or not) Is it because of the Toradex carrier boards ?
Thanks for your answer.
We are already using a proprietary custom carrier board integrating the RS485. We were previously using an Iris, thus not using the RS485.
The module is a Colibri i.MX7D 1GB V1.1 A.
We are wondering whether the “rs485conf.flags |= SER_RS485_RX_DURING_TX;” configuration is truely i.MX dependant as mentionned is the corresponding comment above (UART (Linux) | Toradex Developer Center), or is more logically carrier board dependant.
I have to tell you, that it is indeed iMX dependent. It is caused by a bug in the SoC. This is the reason behind the RX_DURING_TX configuration and you need to keep it in your configuration.
In the schematics of the Colibri Evaluation Board (found here) on the very last page, you can find our implementation of the RS485 interface. It is necessary to implement it in the same way to avoid future issues. This combined with the flag mentioned above the interface should work as intended.
If you have further questions, feel free to reach out again.
Thanks for your quick answer.
That’s very interesting, we will definitely consider it.
Might you please give us more information about this bug in the SoC? What behaviour have you observed?
There was a misunderstanding. The Link stated a bug in SoC which is not related to your question but important for the design of the carrier board.
The Flag ‘RS485_RX_DURING_TX’ is kernel dependant. On your custom carrier Board, you can try to remove the Flag. However all the other mentioned tags are necessary to make RS485 work correctly.
