Configure a USART with the Devicetree Manager

This tutorial sets up a USART on an STM32 board with the Devicetree Manager for Zephyr. The example uses usart2 on a Nucleo H563ZI; the flow is the same on any STM32 board.

Before you start

Install and open the Devicetree Manager as shown in Installing the Devicetree Manager for Zephyr. If you are new to Zephyr on STM32, start with Getting started with Workbench for Zephyr.

1. Pick the USART and enable it

Build your application once, open the Devicetree Manager, and select the USART in the device tree, here usart2. It starts disabled.

usart2 selected, status disabled

Set status to okay. The header now reports two issues: pinctrl-0 and pinctrl-names are empty.

Enabled, pins missing

2. Assign the transmit pin (TX)

Switch to the Chip view; the pads that can carry the usart2 signals light up. Click one, here PD5, and pick the USART2 TX function.

Candidate pads highlighted

Assign TX on PD5

3. Assign the receive pin (RX)

Click another highlighted pad, here PD6, and pick USART2 RX. With both signals set the header reads 0 issues.

Assign RX on PD6

The Properties pane now shows the staged pinctrl-0 with both pins.

Staged pinctrl for usart2

4. Optional: set the baud rate

For a non default baud rate, set current-speed in the Properties pane. It defaults to 115200.

Set current-speed

5. Generate the overlay

Click Generate to write boards/<board>.overlay, then rebuild.

Generated overlay file