RS485 iMX93

[LorenzoSpadaro]

Hi,

I am currently trying to set up an RS485 line using the lpuart2 and lpuart7. In my device tree i added the lines:

&iomuxc {

	pinctrl_uart2: uart2grp {	// RS485_1
		fsl,pins = <
			MX93_PAD_UART2_RXD__LPUART2_RX		0x31e
			MX93_PAD_UART2_TXD__LPUART2_TX		0x31e
			MX93_PAD_SAI1_TXC__LPUART2_CTS_B   0x31e
	
		>;
	};


	pinctrl_uart7: uart7grp { // RS485_2
		fsl,pins = <
			MX93_PAD_GPIO_IO08__LPUART7_TX		0x31e	// TX
			MX93_PAD_GPIO_IO09__LPUART7_RX		0x31e	// RX
			MX93_PAD_GPIO_IO10__LPUART7_CTS_B       0x31e	// DE
		>;
	};

};

for the pin control and these:

&lpuart2 { // RS485_1 pin: p1-72[TX] p1-19[RX] p1-53[DE]
	fsl,uart-has-rtscts;
	rts-gpios = <&gpio1 12 GPIO_ACTIVE_HIGH>;
    linux,rs485-enabled-at-boot-time;  // rs485 abilitata fin da subito al boot
	rs485-rts-active-high;
	rs485-rts-delay = <1 1>;
};

&lpuart7 { // RS485_2 pin: p1-39[TX] p1-41[RX] p1-37[DE]
	uart-has-rtscts;
	rts-gpios = <&gpio2 7 GPIO_ACTIVE_HIGH>;
	linux,rs485-enabled-at-boot-time;  // rs485 abilitata fin da subito al boot
	rs485-rts-active-high;
	rs485-rts-delay = <1 1>;
};

For the peripherals.

I am trying to test the RS485 with a python script. I am currently able to write, but I am not able to read; that is because RTS pin always high. I haven't find a way to make the machine use in the correct way the RTS/CTS pin from the som.

I checked the compatible is the imx93.dtsi file and it seems that the corresponding driver [fsl_lpuart.c] never access the device tree. Instead i have seen that the driver [imx.c] load from device tree some settings about RS485. Is it possible that there are some correlations? Do you know how can i configure the device tree (or the python script in order to make things work?

I attach all the device tree used in the board and the python script used for test.

Thank you in advance

Best regards

Lorenzo

[Chavira]

Hi @LorenzoSpadaro!

Thank you for contacting NXP Support!

You should configure the pins in devcie tree like the UART5 of your dts.

Best Regards!

Chavira

[LorenzoSpadaro]

Which one?
This in the ucm-imx93.dts file:

	pinctrl_uart5: uart5grp { // RS232 pin: p1-67[TX] p2-71[RX]
		fsl,pins = <
			MX93_PAD_DAP_TDI__LPUART5_RX				0x31e
			MX93_PAD_DAP_TDO_TRACESWO__LPUART5_TX		0x31e
		>;
	};

Or this in the ucm-imx93-pinctrl.dtsi file:

pinctrl_uart5: uart5grp {
	fsl,pins = <
		MX93_PAD_GPIO_IO01__LPUART5_RX		0x31e
		MX93_PAD_GPIO_IO00__LPUART5_TX		0x31e
		MX93_PAD_GPIO_IO02__LPUART5_CTS_B	0x31e
		MX93_PAD_GPIO_IO03__LPUART5_RTS_B	0x31e
		MX93_PAD_GPIO_IO18__GPIO2_IO18		0x31e
	>;
};

In case it is the first one, how the peripheral knows which is the pin to use for the DataEnable function of the RS485 tranceiver [THVD1420DR]?