Esp32 Serial Commands

ESP32 Serial Command Emulation

Overview

Send commands directly to the serial port to emulate button presses and user actions. Works over USB serial.

ESP32 Setup (Device Side)

ESP-IDF Framework

#include "esp_log.h"
#include <string.h>

static const char* TAG = "SerialCmd";

void serial_command_task(void* arg) {
    char buf[64];
    int idx = 0;

    while (1) {
        int c = getchar();
        if (c == EOF) {
            vTaskDelay(pdMS_TO_TICKS(10));
            continue;
        }

        if (c == '\n' || c == '\r') {
            buf[idx] = '\0';
            if (idx > 0) {
                ESP_LOGI(TAG, "Command: %s", buf);

                if (strcmp(buf, "PRESS") == 0) {
                    button_callback();
                } else if (strncmp(buf, "SCREEN:", 7) == 0) {
                    int screen = atoi(buf + 7);
                    go_to_screen(screen);
                }
            }
            idx = 0;
        } else if (idx < sizeof(buf) - 1) {
            buf[idx++] = c;
        }
    }
}

// In app_main():
// xTaskCreate(serial_command_task, "serial_cmd", 2048, NULL, 5, NULL);

Arduino Framework

void setup() {
    Serial.begin(115200);
}

void loop() {
    if (Serial.available()) {
        String cmd = Serial.readStringUntil('\n');
        cmd.trim();

        Serial.printf("Command: %s\n", cmd.c_str());

        if (cmd == "PRESS") {
            button_callback();
        } else if (cmd.startsWith("SCREEN:")) {
            int screen = cmd.substring(7).toInt();
            go_to_screen(screen);
        } else if (cmd == "STATUS") {
            Serial.println("OK");
        }
    }
}

Host Side - Send Commands

# Find serial port
PORT=$(ls /dev/cu.usbmodem* /dev/ttyUSB* /dev/ttyACM* 2>/dev/null | head -1)

# Send a command
echo "PRESS" > "$PORT"

Common Command Patterns

# Simple command
echo "PRESS" > "$PORT"

# Command with parameter
echo "PRESS:3" > "$PORT"      # Press 3 times
echo "SCREEN:2" > "$PORT"     # Go to screen 2
echo "MODE:debug" > "$PORT"   # Set debug mode

Automated Testing

Stress Test

PORT=$(ls /dev/cu.usbmodem* /dev/ttyUSB* 2>/dev/null | head -1)
for i in {1..100}; do
  echo "PRESS" > "$PORT"
  echo "Sent press $i"
  sleep 2
done

Long-Duration Stability Test

PORT=$(ls /dev/cu.usbmodem* /dev/ttyUSB* 2>/dev/null | head -1)
END=$(($(date +%s) + 3600))  # 1 hour
count=0

while [ $(date +%s) -lt $END ]; do
  count=$((count + 1))
  echo "PRESS" > "$PORT"
  echo "[$(date +%H:%M:%S)] Press $count"
  sleep 30
done

echo "Total: $count presses"

Test with Log Monitoring

Terminal 1 - Monitor logs:

tail -f /tmp/device.log

Terminal 2 - Send commands:

PORT=$(ls /dev/cu.usbmodem* /dev/ttyUSB* 2>/dev/null | head -1)
echo "PRESS" > "$PORT"

Tips

• Timing: Add delays between commands to let device process
• Feedback: Check serial logs to confirm command was received
• Error handling: Device should echo back status (OK/ERROR)
• Combine with logging: Always monitor logs while testing