How do I configure automatic sending and receiving for 485

gongyaxuan · ‎10-12-2023

Can the 485 driver support 485 automatic enable sending and receiving? If yes, how to configure it

Sanket_Parekh · ‎10-12-2023

I hope you are doing well.

Configuring the 485, depends on which device you are using. What are their configurations? Kindly mention all details of i.MX development board and their prerequisites.

Thanks & Regards,
Sanket Parekh

gongyaxuan · ‎10-15-2023

Thanks

I use imx93 board ,I tried to do this in the device tree, but it didn't seem to work,What is the right configuration

&lpuart3 {

pinctrl-names = "default";

pinctrl-0 = <&pinctrl_uart3>;

rts-gpios = <&at9555 12 GPIO_ACTIVE_HIGH>;

rs485-rx-during-tx;

rs485-rts-active-high;

linux,rs485-enabled-at-boot-time;

status = "okay";

};

Sanket_Parekh · ‎10-16-2023

Hi @gongyaxuan,

I hope you are doing well.

Normally, the UART interface on MCU could act as an RS485 controller with an external transceiver. It provides TTL logical signal and direction control signals; the RS485 transceiver provides voltage level translation, isolation, fault protection, etc. Usually, RS485 communication works in half-duplex mode.

One can find various patches over here to uart drivers: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/tty/serial/imx.c?...

https://groups.google.com/g/linux.kernel/c/61UXsQpy8lo?pli=1

The key to the design of UART to RS485 is how to control the direction of receiving and transmitting data. The above imx.c supports two control modes: GPIO or UART CTS. For the example, please refer below: https://community.nxp.com/t5/i-MX-Processors/Strange-RS485-latency-of-disabling-driver/m-p/984949?co...

UCM-iMX93 port: UART7

Linux device: /dev/ttyLP6

on SB-UCMIMX93 carrier-board: converted to RS485, terminal block

So you can refer to drivers/tty/serial/imx.c , which is a UART driver.

Thanks & Regards,
Sanket Parekh