esp32开发与应用（串口测试）-开发者社区

esp32板子上面有两个串口，一个是串口0，一个是串口2。其中串口0是用做下载image使用的，所以不建议大家使用。所以剩下来的串口2，是大家非常推荐的串口。今天，就来看看esp32里面，串口是怎么使用的。

1、三个串口只能用1个

按照官方的资料说，本身esp32是有多个串口的，但是0和1串口要么被当下载口，要么经常被占用。实际使用的最多的，还是串口2。

2、测试方法

这里的测试方法比较简单，就是一个自环测试。即，所有tx发出来的内容，都会流到rx这边。所以我们需要做的，就是找一根杜邦线，把两者连在一起即可。

3、实际使用方法

实际使用就和常规的串口一样，tx/rx/gnd。比如说，假设需要esp32和stm32，或者是其他arm soc系统进行连接，那么直接tx/rx交叉对接即可。注意，连接的时候，最好gnd也加上。

4、用ai写代码

所有条件都准备好了，就可以让ai写代码。比如，告诉ai，用esp-idf编写一个esp32的串口自环程序。不出意外的话，就能看到这样的结果，

// uart2_loopback_external.c // External loopback test - Requires shorting GPIO16 and GPIO17 with a jumper wire #include <stdio.h> #include <string.h> #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "driver/uart.h" #include "driver/gpio.h" #include "esp_log.h" // Macro definitions #define UART_PORT_NUM UART_NUM_2 #define UART_TX_PIN GPIO_NUM_17 #define UART_RX_PIN GPIO_NUM_16 #define BUF_SIZE 1024 #define TEST_INTERVAL_MS 2000 static const char *TAG = "UART2_EXT_LOOPBACK"; // Send string and read echo back void uart2_echo_test(void) { char *test_str = "Hello UART2! This is a loopback test message.\n"; char rx_buffer[BUF_SIZE]; while (1) { // Clear buffer memset(rx_buffer, 0, sizeof(rx_buffer)); // Send test message int tx_len = uart_write_bytes(UART_PORT_NUM, test_str, strlen(test_str)); ESP_LOGI(TAG, "Sent %d bytes: %s", tx_len, test_str); // Wait for data to return vTaskDelay(pdMS_TO_TICKS(100)); // Read received data int rx_len = uart_read_bytes(UART_PORT_NUM, (uint8_t *)rx_buffer, BUF_SIZE - 1, pdMS_TO_TICKS(500)); if (rx_len > 0) { rx_buffer[rx_len] = '\0'; // Verify data consistency if (strcmp(test_str, rx_buffer) == 0) { ESP_LOGI(TAG, "✓ Echo test PASSED - received: %s", rx_buffer); } else { ESP_LOGW(TAG, "✗ Echo test FAILED - sent: %s", test_str); ESP_LOGW(TAG, " received: %s", rx_buffer); } } else { ESP_LOGW(TAG, "✗ Echo test FAILED - no data received"); ESP_LOGW(TAG, "Please check: Are GPIO%d and GPIO%d shorted?", UART_TX_PIN, UART_RX_PIN); } vTaskDelay(pdMS_TO_TICKS(TEST_INTERVAL_MS)); } } // Byte-level loopback test (more precise verification) void uart2_byte_loopback_test(void) { uint8_t tx_data[BUF_SIZE]; uint8_t rx_data[BUF_SIZE]; // Initialize test data (0-255 cycle) for (int i = 0; i < BUF_SIZE; i++) { tx_data[i] = i % 256; } int test_count = 0; int success_count = 0; while (1) { test_count++; // Send data uart_write_bytes(UART_PORT_NUM, (const char *)tx_data, BUF_SIZE); // Wait for data to return vTaskDelay(pdMS_TO_TICKS(100)); // Read data int rx_len = uart_read_bytes(UART_PORT_NUM, rx_data, BUF_SIZE, pdMS_TO_TICKS(500)); if (rx_len == BUF_SIZE) { bool match = memcmp(tx_data, rx_data, BUF_SIZE) == 0; if (match) { success_count++; ESP_LOGI(TAG, "Test #%d: ✓ PASSED (%d bytes matched)", test_count, rx_len); } else { // Find the first mismatched position for (int i = 0; i < BUF_SIZE; i++) { if (tx_data[i] != rx_data[i]) { ESP_LOGE(TAG, "Mismatch at offset %d: 0x%02X != 0x%02X", i, tx_data[i], rx_data[i]); break; } } } } else { ESP_LOGW(TAG, "Test #%d: ✗ FAILED (expected %d bytes, got %d)", test_count, BUF_SIZE, rx_len); } ESP_LOGI(TAG, "Success rate: %d/%d (%.1f%%)", success_count, test_count, (float)success_count * 100 / test_count); vTaskDelay(pdMS_TO_TICKS(TEST_INTERVAL_MS)); } } void app_main(void) { ESP_LOGI(TAG, "=== ESP32 UART2 External Loopback Test ==="); ESP_LOGI(TAG, "Hardware: Please short GPIO%d (TX) and GPIO%d (RX)", UART_TX_PIN, UART_RX_PIN); // 1. Configure UART parameters uart_config_t uart_config = { .baud_rate = 115200, .data_bits = UART_DATA_8_BITS, .parity = UART_PARITY_DISABLE, .stop_bits = UART_STOP_BITS_1, .flow_ctrl = UART_HW_FLOWCTRL_DISABLE, .source_clk = UART_SCLK_APB, }; ESP_ERROR_CHECK(uart_param_config(UART_PORT_NUM, &uart_config)); // 2. Set pins ESP_ERROR_CHECK(uart_set_pin(UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE)); // 3. Install driver (Note: hardware loopback is NOT enabled here) const int uart_buffer_size = BUF_SIZE * 2; ESP_ERROR_CHECK(uart_driver_install(UART_PORT_NUM, uart_buffer_size, uart_buffer_size, 10, NULL, 0)); ESP_LOGI(TAG, "UART2 initialized successfully"); ESP_LOGI(TAG, "Starting echo test..."); // Run test (choose one) //uart2_echo_test(); uart2_byte_loopback_test(); }

官方给了两个测试函数，一个是uart2_echo_test，还有一个是uart2_byte_loopback_test。实际测试的时候，只需要放开一个。