PROCESSOR-SDK-AM335X: UART configuration

Hi Sergej,

The question has been asked and answered many time on this e2e forum. You can find the details by searching on this forum.

In general to enable a UART you only need to modify the kernel device tree file: configure the pinmux and enable the uart node. But first you would also have to check the board schematics to ensure the UART1/2/4 have pins available for your access, and if any of the pins is used by default for a different function, you would have to disable the function or pinmux in device tree so that you can set the pinmux for UART.

Because the EVM has many functions, you might have difficulty to find all the UART 1/2/4 pins accessible, then you might want to take a look at Beaglebone Black board, which also uses AM335x processor but has most pins on two expansion connectors.

For your reference, below is the patch I use to enable UART1 on Beaglebone Black.

diff --git a/arch/arm/boot/dts/am335x-bone-common.dtsi b/arch/arm/boot/dts/am335x-bone-common.dtsi
index e13aed096328..57f6159d6cb6 100644
--- a/arch/arm/boot/dts/am335x-bone-common.dtsi
+++ b/arch/arm/boot/dts/am335x-bone-common.dtsi
@@ -99,6 +99,13 @@
                >;
        };
 
+       uart1_pins: pinmux_uart1_pins {
+               pinctrl-single,pins = <
+                       AM33XX_IOPAD(0x980, PIN_INPUT_PULLUP | MUX_MODE0)       /* uart1_rxd.uart1_rxd */
+                       AM33XX_IOPAD(0x984, PIN_OUTPUT_PULLDOWN | MUX_MODE0)    /* uart1_txd.uart1_txd */
+               >;
+       };
+
        clkout2_pin: pinmux_clkout2_pin {
                pinctrl-single,pins = <
                        AM33XX_IOPAD(0x9b4, PIN_OUTPUT_PULLDOWN | MUX_MODE3)    /* xdma_event_intr1.clkout2 */
@@ -195,6 +202,13 @@
        status = "okay";
 };
 
+&uart1 {
+       pinctrl-names = "default";
+       pinctrl-0 = <&uart1_pins>;
+
+       status = "okay";
+};
+
 &usb {
        status = "okay";
 };