[PATCH v5 2/6] serial: 8250: Support separate rs485 rx-enable GPIO

Farouk Bouabid farouk.bouabid at theobroma-systems.com
Thu Feb 8 07:46:18 PST 2024

Hi Christoph,

On 30.01.24 13:29, Christoph Niedermaier wrote:
> [Einige Personen, die diese Nachricht erhalten haben, erhalten häufig keine E-Mails von cniedermaier at dh-electronics.com. Weitere Informationen, warum dies wichtig ist, finden Sie unter https://aka.ms/LearnAboutSenderIdentification ]
> From: Farouk Bouabid
> Sent: Monday, January 29, 2024 9:57 AM
> Hi,
>> On 26.01.24 20:58, Lino Sanfilippo wrote:
>>> [Some people who received this message don't often get email from linosanfilippo at gmx.de. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>>> Hi,
>>> On 26.01.24 18:27, Farouk Bouabid wrote:
>>>> From: Heiko Stuebner <heiko.stuebner at cherry.de>
>>>> The RE signal is used to control the duplex mode of transmissions,
>>>> aka receiving data while sending in full duplex mode, while stopping
>>>> receiving data in half-duplex mode.
>>>> On a number of boards the !RE signal is tied to ground so reception
>>>> is always enabled except if the UART allows disabling the receiver.
>>>> This can be taken advantage of to implement half-duplex mode - like
>>>> done on 8250_bcm2835aux.
>>>> Another solution is to tie !RE to RTS always forcing half-duplex mode.
>>>> And finally there is the option to control the RE signal separately,
>>>> like done here by introducing a new rs485-specific gpio that can be
>>>> set depending on the RX_DURING_TX setting in the common em485 callbacks.
>>> we just added the rx_during_tx_gpio to the serial core.
>>> Why cant you use this GPIO for your purpose?
>>> Regards,
>>> Lino.
>> What we are trying to implement is a gpio that emulates the RTS signal
>> itself as we do not have a dedicated RTS signal that can be controlled
>> through MCR. The rx during tx state in our case is a fixed state of
> Why can't the property rts-gpios be used here for this purpose?

Yes that indeed serves our purpose. Thank you for the suggestion.



> Regards
> Christoph

More information about the Linux-rockchip mailing list