Hi,
Here is sample of UART4 RS485:
dts-v1/;
/plugin/;
#include <dt-bindings/board/am335x-bbw-bbb-base.h>
#include <dt-bindings/pinctrl/am33xx.h>
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black", "ti,beaglebone-green";
// identification
part-number = "BB-UART4-COM0";
version = "00A0";
// resources this cape uses
exclusive-use =
"P9.13", // uart4_txd
"P9.11", // uart4_rxd
"P8.35", // uart4_de/re
"gpio0_8",
"uart4"; // hardware ip used
/*
* Free up the pins used by the cape from the pinmux helpers.
*/
fragment@0 {
target = <&ocp>;
__overlay__ {
P9_13_pinmux { status = "disabled"; }; /* P9_13: gpmc_wpn.uart4_txd_mux2 */
P9_11_pinmux { status = "disabled"; }; /* P9_11: gpmc_wait0.uart4_rxd_mux2
*/
P8_35_pinmux { status = "disabled"; }; /* P8_35: PIN_OUTPUT_PULLDOWN |
MUX_MODE7 (GPIO0_8) */
};
};
fragment@1 {
target = <&am33xx_pinmux>;
__overlay__ {
bb_uart4_rs485_pins: pinmux_bb_uart4_rs485_pins {
pinctrl-single,pins = <
BONE_P9_13 (PIN_OUTPUT | MUX_MODE6) /* P9_13: gpmc_wpn.uart4_txd_mux2 */
BONE_P9_11 (PIN_INPUT | MUX_MODE6) /* P9_11: gpmc_wait0.uart4_rxd_mux2 */
BONE_P8_35 0x07 /* P8_35: PIN_OUTPUT_PULLDOWN | MUX_MODE7 (GPIO0_8) */
>;
};
};
};
fragment@2 {
target = <&uart4>;
__overlay__ {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&bb_uart4_rs485_pins>;
rs485-rts-delay = <0 0>;
rts-gpio = <&gpio0 8 1>; /* GPIO_ACTIVE_HIGH>; */
rs485-rts-active-high;
linux,rs485-enabled-at-boot-time;
};
};
};
Regards,
Atique
On Tue, Jan 19, 2021 at 7:19 PM Jørgen Sirum <[email protected]> wrote:
> Struggling to get RS485 to work with overlays
> I have been using kernel 3.8.13 (enabling RS485 with python script) with
> no issues but wanted to upgrade into the modern world.
> Used default image and did the steps suggested in this post:
> https://groups.google.com/g/beagleboard/c/nMtRpdWSJu0/m/USjb8sF-AgAJ
>
> - Swapped from CONFIG_SERIAL_8250_OMAP to CONFIG_SERIAL_OMAP and rebuild
> - Used BB-UART4-RS485-00A0.dts but modified it to be for UART1 and the
> direction pin I am using
> Everything else is untouched
>
> BB-UART1-RS485-00A0.dts:
> /dts-v1/;
> /plugin/;
>
> #include <dt-bindings/board/am335x-bbw-bbb-base.h>
> #include <dt-bindings/pinctrl/am33xx.h>
>
> / {
> compatible = "ti,beaglebone", "ti,beaglebone-black",
> "ti,beaglebone-green";
>
> // identification
> part-number = "BB-UART1-RS485";
> version = "00A0";
>
> // resources this cape uses
> exclusive-use =
> "P9.24", // uart1_txd
> "P9.26", // uart1_rxd
> "P8.14", // uart1_de/re
> "gpio0_26",
>
> "uart1"; // hardware ip used
>
> /*
> * Helper to show loaded overlays under:
> /proc/device-tree/chosen/overlays/
> */
> fragment@0 {
> target-path="/";
> __overlay__ {
>
> chosen {
> overlays {
> BB-UART1-RS485-00A0 = __TIMESTAMP__;
> };
> };
> };
> };
>
> /*
> * Free up the pins used by the cape from the pinmux helpers.
> */
> fragment@1 {
> target = <&ocp>;
> __overlay__ {
> P9_24_pinmux { status = "disabled"; };
> P9_26_pinmux { status = "disabled"; };
> P8_14_pinmux { status = "disabled"; };
> };
> };
>
> fragment@2 {
> target = <&am33xx_pinmux>;
> __overlay__ {
> bb_uart1_rs485_pins: pinmux_bb_uart1_rs485_pins {
> pinctrl-single,pins = <
> BONE_P9_24 (PIN_OUTPUT | MUX_MODE6)
> BONE_P9_26 (PIN_INPUT | MUX_MODE6)
> BONE_P8_14 0x07
> >;
> };
> };
> };
>
> fragment@3 {
> target = <&uart1>;
> __overlay__ {
> status = "okay";
> pinctrl-names = "default";
> pinctrl-0 = <&bb_uart1_rs485_pins>;
> rs485-rts-delay = <0 0>;
>
> rts-gpio = <&gpio0 26 1>; /* GPIO_ACTIVE_HIGH>; */
> rs485-rts-active-high;
> linux,rs485-enabled-at-boot-time;
> };
> };
> };
>
> /boot/uEnv.txt:
>
> enable_uboot_overlays=1
> uboot_overlay_addr0=/lib/firmware/BB-UART1-RS485-00A0.dtbo
> disable_uboot_overlay_video=1
> disable_uboot_overlay_audio=1
> disable_uboot_overlay_wireless=1
> disable_uboot_overlay_adc=1
>
>
> When I boot:
>
> [ 0.460625] 44e09000.serial: ttyO0 at MMIO 0x44e09000 (irq = 30,
> base_baud = 3000000) is a OMAP UART0
> [ 0.472149] 48022000.serial: ttyO1 at MMIO 0x48022000 (irq = 31,
> base_baud = 3000000) is a OMAP UART1
>
> But it doesnt work.
> If I use the normal overlay BB-UART1-00A0.dtbo and swap the direction pin
> manually it works.
>
> Any help would be very appreciatied!
>
> Jørgen
>
>
> --
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> .
>
--
Regards,
Atique u Rehman
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