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Table of Contents
UART
Introduction
This document mainly introduces the usage of UART on 40-Pin Header.
UART Information
| UART | PIN & GPIO(#Number) | DT Overlays Node | Device Node | |
|---|---|---|---|---|
| VIM1/2 | UART_AO_B | RX(15) - GPIOAO_5(#506) TX(16) - GPIOAO_4(#505) | uart4 | /dev/ttyS4 |
| VIM3/3L | UART_C | RX(15) - GPIOH_6(#433) TX(16) - GPIOH_7(#434) | uart3 | /dev/ttyS3 |
| VIM4 | UART_E | RX(15) - GPIOY_7(#491) TX(16) - GPIOY_6(#490) | uart_e | /dev/ttyS4 |
Enable UART
In order to use the UART, you need to enable the UART function via Device Tree Overlay.
VIM1/2/3/3L/Edge1
Edit /boot/env.txt to add the uart node to overlays node if it doesn't exist.
Take VIM3 as an example to enable UART_C, you need to add uart3 node to overlays node if it doesn't exist.
overlays=pwm_ao_a pwm_f uart3
After reboot, you will see the UART device node.
$ ls /dev/ttyS3
/dev/ttyS3
VIM4
Edit /boot/dtb/amlogic/kvim4.dtb.overlay.env to add uart node to fdt_overlays node if it doesn't exist.
e.g. Enable UART_E, you need to add uart_e to node fdt_overlays if it doesn't exist.
fdt_overlays=uart_e
After reboot, you will see the UART device node.
$ ls /dev/ttyS4
/dev/ttyS4
Disable UART to Use GPIO
If you want to use normal GPIO instead of UART, you can remove the UART node in device tree overlays configration file.