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--- products:sbc:edge2:applications:gpio:uart [2022/11/20 22:02]
ivan created
+++ products:sbc:edge2:applications:gpio:uart [2023/08/13 22:40] (current)
jacobe
@@ Line 1: / Line 1: @@
+~~tag>Edge2 UART~~
 ====== Edge2 UART ======
-{{page>products:sbc:common:applications:gpio:uart&noheader}}
+===== Introduction =====
+This page introduces the usage of hardware UART on [[products:sbc:edge2:applications:gpio:40pin-header|16-pin Header]].
+<WRAP important >
+For Edge2, in order to use the UART , you need to attach the IO extension board.
+</WRAP>
+===== UART Information =====
+|           ^  UART       ^ PIN      ^ GPIO Name  ^ GPIO Number  ^  DT Overlays Node  ^  Device Node  ^
+^  Edge2    |  UART7      |  12(TX)  |  GPIO3_C0  |  112         |  edge2-io-uart     |  /dev/ttyS7   |
+| :::       | :::         |  14(RX)  |  GPIO3_C1  |  113         | :::                | :::           |
+===== Enable UART =====
+In order to use the UART, you need to enable the UART function via [[products:sbc:common:configurations:device-tree-overlay|Device Tree Overlay]].
+Edit ''/boot/dtb/rockchip/rk3588s-khadas-edge2.dtb.overlay.env'' to add uart node to ''fdt_overlays'' node if it doesn't exist.
+e.g. Enable ''UART7'', you need to add ''edge2-io-uart'' to node ''fdt_overlays'' if it doesn't exist.
+```shell
+fdt_overlays=edge2-io-uart
+```
+After reboot, you will see the UART device node.
+```shell
+$ ls /dev/ttyS7
+/dev/ttyS7
+```
+===== 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 serial path
+#define SERIAL_PORT "/dev/ttyS7"
+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, B1500000); // set baud rate
+    cfsetispeed(&tty, B1500000);
+    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
+```
+Run ''uart''
+```
+$ ./uart
+```
+After connecting PIN12(STX), PIN14(CSO) and GND to PC, open ttyUSBX and input hello
+```
+hello
+Hello, UART!
+```
+Check output data:
+```
+$ ./uart
+Received: hello
+```
+===== Disable UART to Use GPIO =====
+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]].

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