Khadas Docs

Amazing Khadas, always amazes you!

User Tools

Site Tools

Home / products / sbc / common / applications / gpio / uart
products:sbc:common:applications:gpio:uart

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision 		Previous revision
Last revision Both sides next revision
products:sbc:common:applications:gpio:uart [2022/07/04 07:36]
frank add uart 		products:sbc:common:applications:gpio:uart [2023/11/07 05:09]
nick [Enable UART]
Line 3: Line 3:
 ===== Introduction ===== ===== Introduction =====
  
-This document mainly introduces UART. You will learn how to enable UART on 40-Pin Header on Khadas SBC.+This page introduces the usage of UART on [[products:sbc:common:applications:gpio:40pin-header|40pin-Header]].
  
 +===== UART Information =====
 +
 +|           ^  UART       ^ PIN      ^ GPIO Name  ^  DT Overlays Node  ^  Device Node  ^
 +^  VIM1/2   |  UART_AO_B  |  15(RX)  |  GPIOAO_5  |  uart4             |  /dev/ttyS4   |
 +| :::       | :::         |  16(TX)  |  GPIOAO_4  | :::                | :::           |
 +^  VIM3/3L  |  UART_C     |  15(RX)  |  GPIOH_6   |  uart3             |  /dev/ttyS3   |
 +| :::       | :::         |  16(TX)  |  GPIOH_7   | :::                | :::           |
 +^  VIM4     |  UART_E     |  15(RX)  |  GPIOY_7   |  uart_e            |  /dev/ttyS4   |
 +| :::       | :::         |  16(TX)  |  GPIOY_6   | :::                | :::           |
 +^  VIM1S    |  UART_C     |  15(RX)  |  GPIOD_3   |  uart_c            |  /dev/ttyS2   |
 +| :::       | :::         |  16(TX)  |  GPIOD_2   | :::                | :::           |
 ===== Enable UART ===== ===== Enable UART =====
  
-Uart PIN in 40-Pin Header is PIN15 and PIN16. Refer to [[/products/sbc/vim4/configuration/device-tree-overlay|Device Tree Overlay]].+In order to use the UART, you need to enable the UART function via [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].
  
-Enable uart node via device tree overlays. Edit ''/boot/env.txt'' to add ''uartX'' to overlays. E.g.+<tabbox VIM1/2/3/3L/Edge1>
  
-```sh +Edit ''/boot/env.txt'' to add the uart node to ''overlays'' node if it doesn't exist. 
-overlays=uart4 pwm_ao_a pwm_f i2c0+ 
 +Take VIM3 as an example to enable ''UART_C'', you need to add ''uart3'' node to ''overlays'' node if it doesn't exist. 
 + 
 +```shell 
 +overlays=pwm_ao_a pwm_f uart3
 ``` ```
  
-Reboot to effect.+After reboot, you will see the UART device node.
  
-<WRAP info > +```shell 
-  * VIM1/VIM2/VIM4 - uar4 +$ ls /dev/ttyS3 
-  * VIM3/VIM3L - uart3 +/dev/ttyS3 
-</WRAP>+```
  
 +<tabbox VIM3 with 5.15 kernel>
 +
 +Edit ''/boot/dtb/amlogic/kvim3.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.
 +
 +```shell
 +fdt_overlays=uart_e
 +
 +```
 +
 +After reboot, you will see the UART device node.
 +
 +```shell
 +$ ls /dev/ttyS4
 +/dev/ttyS4
 +```
 +
 +<tabbox VIM3L with 5.15 kernel>
 +
 +Edit ''/boot/dtb/amlogic/kvim3l.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.
 +
 +```shell
 +fdt_overlays=uart_e
 +
 +```
 +
 +After reboot, you will see the UART device node.
 +
 +```shell
 +$ ls /dev/ttyS4
 +/dev/ttyS4
 +```
 +
 +<tabbox 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.
 +
 +```shell
 +fdt_overlays=uart_e
 +
 +```
 +
 +After reboot, you will see the UART device node.
 +
 +```shell
 +$ ls /dev/ttyS4
 +/dev/ttyS4
 +```
 +
 +<tabbox VIM1S>
 +
 +Edit ''/boot/dtb/amlogic/kvim1s.dtb.overlay.env'' to add uart node to ''fdt_overlays'' node if it doesn't exist.
 +
 +
 +e.g. Enable ''UART_C'', you need to add ''uart_c'' to node ''fdt_overlays'' if it doesn't exist.
 +
 +```shell
 +fdt_overlays=uart_c
 +
 +```
 +
 +After reboot, you will see the UART device node.
 +
 +```shell
 +$ ls /dev/ttyS2
 +/dev/ttyS2
 +```
 +
 +</tabbox>
 +
 +===== Demo Source Code =====
 +```c uart.c
 +#include <stdio.h>
 +#include <stdlib.h>
 +#include <string.h>
 +#include <fcntl.h>
 +#include <unistd.h>
 +#include <termios.h>
 +
 +// set correct serial path
 +#define SERIAL_PORT "/dev/ttyS2"
 +
 +int main() {
 +    int serial_port;
 +    struct termios tty;
 +    
 +    // open
 +    serial_port = open(SERIAL_PORT, O_RDWR | O_NOCTTY);
 +    if (serial_port < 0) {
 +        perror("Error opening serial port");
 +        return 1;
 +    }
 +    
 +    // Configuration of serial
 +    memset(&tty, 0, sizeof(tty));
 +    if (tcgetattr(serial_port, &tty) != 0) {
 +        perror("Error getting serial port attributes");
 +        close(serial_port);
 +        return 1;
 +    }
 +    
 +    cfsetospeed(&tty, B921600); // set correct baud rate
 +    cfsetispeed(&tty, B921600);
 +    
 +    tty.c_cflag |= (CLOCAL | CREAD);
 +    tty.c_cflag &= ~PARENB;     
 +    tty.c_cflag &= ~CSTOPB;     
 +    tty.c_cflag &= ~CSIZE;
 +    tty.c_cflag |= CS8;         
 +    
 +    // write configration to serial
 +    if (tcsetattr(serial_port, TCSANOW, &tty) != 0) {
 +        perror("Error setting serial port attributes");
 +        close(serial_port);
 +        return 1;
 +    }
 +    
 +    // loop test
 +    while (1) {
 +        // receive data
 +        char received_data[64];
 +        if (read(serial_port, &received_data, sizeof(char)*64)) {
 +            // get data
 +            printf("Received: %s", received_data);
 +        }
 +
 +        // Only send "Hello, UART!"
 +        char data_to_send[] = "Hello, UART!\n";
 +        write(serial_port, data_to_send, strlen(data_to_send));
 +        
 +        // sleep 100ms
 +        usleep(100000); 
 +    }
 +    
 +    // close
 +    close(serial_port);
 +    
 +    return 0;
 +}
 +```
 +
 +Compile test code:
 +
 +```
 +$ gcc uart.c -o uart
 +```
 +
 +===== Test demonstration =====
 +
 +Run ''uart''
 +
 +```
 +$ ./uart
 +```
 +
 +After connecting PIN15, PIN16 and GND to PC, open ttyUSBX and input hello
 +
 +```
 +1 hello
 +2 Hello, UART!
 +```
 +
 +Check output data:
 +
 +```
 +$ ./uart
 +Received: hello
 +```
  
-===== Check UART Node =====+===== Disable UART to Use GPIO =====
  
-After reboot, you will see the uart device node.+If you want to use normal GPIO instead of UART, you can remove the UART node in [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].
  
-  * VIM1/VIM2/VIM4 - /dev/ttyS4 
-  * VIM3/VIM3L - /dev/ttyS3 
Last modified: 2023/11/07 05:09 by nick

Page Tools

Khadas Site

Khadas Community

Khadas GitHub

Khadas Downloads