ESP32学习笔记之UART

第一部分UART 核心概念1. 什么是 UARTUART 中文常叫“通用异步收发器”“异步”意思是通信双方不共享时钟所以要提前约定好通信参数。 UART 本质上就是按约定好的速度把 0 和 1 一位一位串行发出去关键特点串行通信一位一位传节省引脚异步通信无时钟线靠约定波特率全双工可同时收发点对点通常两个设备直连更详细的UART知识https://blog.csdn.net/2301_81636338/article/details/157764671?spm1011.2124.3001.62092. 一帧数据的组成起始位1 位标志传输开始数据位5~9 位常用 8 位校验位可选奇校验 / 偶校验 / 无校验停止位1 或 2 位标志帧结束常见配置8N18 数据位无校验1 停止位1 起始 8 数据 1 停止 10 位 / 字节3. 波特率定义每秒传输的 bit 数例9600 波特 9600 bit/s ≈960 字节/秒因为 1 字节占 10 位4. 为什么需要起始位和停止位因为没有时钟线接收方需要通过起始位同步知道“数据开始了”按约定时间采样每位通过停止位知道“这一帧结束了”5. UART vs I2C vs SPI特性UARTI2CSPI同步/异步异步同步同步双工方式全双工半双工全双工线数2 (TX, RX) 地2 (SDA, SCL)4 (SCK, MOSI, MISO, CS)设备数点对点多设备地址一主多从片选第二部分UART 常见问题与排查参数不一致检查波特率、数据位、停止位、校验位是否匹配接线问题TX ↔ RX 交叉连接共地GND 必须相连软件问题缓冲区溢出接收处理不及时中断优先级、任务调度第三部分ESP32 UART 实践UART 初始化步骤配置参数结构体uart_config_t波特率、数据位、停止位、校验位等设置引脚uart_set_pin()安装驱动uart_driver_install()收发数据循环发送 Helloc #include stdio.h #include string.h #include freertos/FreeRTOS.h #include freertos/task.h #include driver/uart.h #include esp_err.h #define UART_PORT_NUM UART_NUM_1 #define UART_BAUD_RATE 115200 #define UART_TX_PIN 17 #define UART_RX_PIN 18 #define UART_BUF_SIZE 1024 void app_main(void) { uart_config_t uart_config { .baud_rate UART_BAUD_RATE, .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_DEFAULT, }; ESP_ERROR_CHECK(uart_param_config(UART_PORT_NUM, uart_config)); ESP_ERROR_CHECK(uart_set_pin( UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE)); ESP_ERROR_CHECK(uart_driver_install( UART_PORT_NUM, UART_BUF_SIZE, UART_BUF_SIZE, 0, NULL, 0)); const char *msg Hello from ESP32-S3 UART1\r\n; while (1) { uart_write_bytes(UART_PORT_NUM, msg, strlen(msg)); printf(UART1 sent: %s, msg); vTaskDelay(pdMS_TO_TICKS(1000)); } }回显Echoc #include stdio.h #include string.h #include freertos/FreeRTOS.h #include freertos/task.h #include driver/uart.h #include esp_err.h #define UART_PORT_NUM UART_NUM_1 #define UART_BAUD_RATE 115200 #define UART_TX_PIN 17 #define UART_RX_PIN 16 #define UART_BUF_SIZE 1024 void app_main(void) { uart_config_t uart_config { .baud_rate UART_BAUD_RATE, .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_DEFAULT, }; ESP_ERROR_CHECK(uart_param_config(UART_PORT_NUM, uart_config)); ESP_ERROR_CHECK(uart_set_pin( UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE)); ESP_ERROR_CHECK(uart_driver_install( UART_PORT_NUM, UART_BUF_SIZE, UART_BUF_SIZE, 0, NULL, 0)); uint8_t data[UART_BUF_SIZE]; while (1) { int len uart_read_bytes( UART_PORT_NUM, data, UART_BUF_SIZE - 1, pdMS_TO_TICKS(100)); if (len 0) { data[len] \0; printf(UART1 received: %s\n, (char *)data); uart_write_bytes(UART_PORT_NUM, (const char *)data, len); } } }中断方式事件队列使用队列接收 UART 事件数据到达、溢出、错误等适合需要高效处理、不丢数据的场景#include stdio.h #include string.h #include freertos/FreeRTOS.h #include freertos/task.h #include freertos/queue.h #include driver/uart.h #include esp_err.h #include esp_log.h #define UART_PORT_NUM UART_NUM_1 #define UART_BAUD_RATE 115200 #define UART_TX_PIN 17 #define UART_RX_PIN 16 #define UART_BUF_SIZE 1024 #define UART_QUEUE_SIZE 20 static const char *TAG uart1_intr; static QueueHandle_t uart_queue; static void uart_event_task(void *pvParameters) { uart_event_t event; uint8_t data[UART_BUF_SIZE]; while (1) { if (xQueueReceive(uart_queue, event, portMAX_DELAY)) { switch (event.type) { case UART_DATA: int len uart_read_bytes( UART_PORT_NUM, data, event.size UART_BUF_SIZE - 1 ? event.size : UART_BUF_SIZE - 1, 0); if (len 0) { data[len] \0; ESP_LOGI(TAG, recv: %s, (char *)data); uart_write_bytes(UART_PORT_NUM, (const char *)data, len); } break; case UART_FIFO_OVF: case UART_BUFFER_FULL: ESP_LOGW(TAG, overflow or buffer full); uart_flush_input(UART_PORT_NUM); xQueueReset(uart_queue); break; case UART_BREAK: case UART_PARITY_ERR: case UART_FRAME_ERR: ESP_LOGW(TAG, error event: %d, event.type); break; default: break; } } } } void app_main(void) { uart_config_t uart_config { .baud_rate UART_BAUD_RATE, .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_DEFAULT, }; ESP_ERROR_CHECK(uart_param_config(UART_PORT_NUM, uart_config)); ESP_ERROR_CHECK(uart_set_pin( UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE)); ESP_ERROR_CHECK(uart_driver_install( UART_PORT_NUM, UART_BUF_SIZE, UART_BUF_SIZE, UART_QUEUE_SIZE, uart_queue, 0)); xTaskCreate(uart_event_task, uart_event_task, 4096, NULL, 12, NULL); ESP_LOGI(TAG, UART1 interrupt event echo started); }DMA 方式高性能#include stdio.h #include string.h #include freertos/FreeRTOS.h #include freertos/task.h #include driver/uart.h #include esp_attr.h #include esp_log.h #include esp_private/gdma.h #include esp_private/periph_ctrl.h #include hal/uhci_ll.h #include soc/lldesc.h #define UART_PORT_NUM UART_NUM_1 #define UART_BAUD_RATE 115200 #define UART_TX_PIN 17 #define UART_RX_PIN 16 #define DMA_RX_BUF_SIZE 1024 #define DMA_TX_BUF_SIZE 1024 #define DMA_DESC_NUM 1 #define UART_RX_TOUT_THRESH 10 #define TASK_STACK_SIZE 4096 #define RX_DONE_BIT (1U 0) #define TX_DONE_BIT (1U 1) static const char *TAG uart_dma_echo; static volatile uhci_dev_t *s_uhci_hw UHCI0; static gdma_channel_handle_t s_rx_channel; static gdma_channel_handle_t s_tx_channel; static TaskHandle_t s_dma_task_hdl; DMA_ATTR static uint8_t s_rx_buf[DMA_RX_BUF_SIZE]; DMA_ATTR static uint8_t s_tx_buf[DMA_TX_BUF_SIZE]; DMA_ATTR static lldesc_t s_rx_desc[DMA_DESC_NUM]; DMA_ATTR static lldesc_t s_tx_desc[DMA_DESC_NUM]; static bool IRAM_ATTR rx_eof_callback(gdma_channel_handle_t dma_chan, gdma_event_data_t *event_data, void *user_data) { BaseType_t high_task_wakeup pdFALSE; (void)dma_chan; (void)event_data; (void)user_data; xTaskNotifyFromISR(s_dma_task_hdl, RX_DONE_BIT, eSetBits, high_task_wakeup); return high_task_wakeup pdTRUE; } static bool IRAM_ATTR tx_eof_callback(gdma_channel_handle_t dma_chan, gdma_event_data_t *event_data, void *user_data) { BaseType_t high_task_wakeup pdFALSE; (void)dma_chan; (void)event_data; (void)user_data; xTaskNotifyFromISR(s_dma_task_hdl, TX_DONE_BIT, eSetBits, high_task_wakeup); return high_task_wakeup pdTRUE; } static void start_rx_dma(void) { memset(s_rx_buf, 0, sizeof(s_rx_buf)); memset(s_rx_desc, 0, sizeof(s_rx_desc)); lldesc_setup_link(s_rx_desc, s_rx_buf, DMA_RX_BUF_SIZE, true); ESP_ERROR_CHECK(gdma_reset(s_rx_channel)); ESP_ERROR_CHECK(gdma_start(s_rx_channel, (intptr_t)s_rx_desc[0])); } static void start_tx_dma(const uint8_t *data, size_t len) { if (len 0 || len DMA_TX_BUF_SIZE) { return; } memcpy(s_tx_buf, data, len); memset(s_tx_desc, 0, sizeof(s_tx_desc)); lldesc_setup_link(s_tx_desc, s_tx_buf, len, false); ESP_ERROR_CHECK(gdma_reset(s_tx_channel)); ESP_ERROR_CHECK(gdma_start(s_tx_channel, (intptr_t)s_tx_desc[0])); } static void uart_dma_init(void) { periph_module_enable(PERIPH_UHCI0_MODULE); periph_module_reset(PERIPH_UHCI0_MODULE); periph_module_enable(PERIPH_UART1_MODULE); periph_module_reset(PERIPH_UART1_MODULE); uart_config_t uart_config { .baud_rate UART_BAUD_RATE, .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_DEFAULT, }; ESP_ERROR_CHECK(uart_param_config(UART_PORT_NUM, uart_config)); ESP_ERROR_CHECK(uart_set_pin(UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE)); // 设置 UART 空闲超时空闲一小段时间就认为一帧结束 ESP_ERROR_CHECK(uart_set_rx_timeout(UART_PORT_NUM, UART_RX_TOUT_THRESH)); gdma_channel_alloc_config_t tx_config { .direction GDMA_CHANNEL_DIRECTION_TX, .flags.reserve_sibling 1, }; ESP_ERROR_CHECK(gdma_new_channel(tx_config, s_tx_channel)); gdma_channel_alloc_config_t rx_config { .direction GDMA_CHANNEL_DIRECTION_RX, .sibling_chan s_tx_channel, }; ESP_ERROR_CHECK(gdma_new_channel(rx_config, s_rx_channel)); ESP_ERROR_CHECK(gdma_connect(s_tx_channel, GDMA_MAKE_TRIGGER(GDMA_TRIG_PERIPH_UHCI, 0))); ESP_ERROR_CHECK(gdma_connect(s_rx_channel, GDMA_MAKE_TRIGGER(GDMA_TRIG_PERIPH_UHCI, 0))); gdma_strategy_config_t strategy { .auto_update_desc false, .owner_check false, }; ESP_ERROR_CHECK(gdma_apply_strategy(s_tx_channel, strategy)); ESP_ERROR_CHECK(gdma_apply_strategy(s_rx_channel, strategy)); gdma_rx_event_callbacks_t rx_cbs { .on_recv_eof rx_eof_callback, }; ESP_ERROR_CHECK(gdma_register_rx_event_callbacks(s_rx_channel, rx_cbs, NULL)); gdma_tx_event_callbacks_t tx_cbs { .on_trans_eof tx_eof_callback, }; ESP_ERROR_CHECK(gdma_register_tx_event_callbacks(s_tx_channel, tx_cbs, NULL)); uhci_ll_init((uhci_dev_t *)s_uhci_hw); uhci_ll_set_eof_mode((uhci_dev_t *)s_uhci_hw, UHCI_RX_IDLE_EOF); s_uhci_hw-escape_conf.val 0; uhci_ll_attach_uart_port((uhci_dev_t *)s_uhci_hw, 1); } static void dma_echo_task(void *arg) { uint32_t notify_value 0; (void)arg; start_rx_dma(); while (1) { xTaskNotifyWait(0, UINT32_MAX, notify_value, portMAX_DELAY); if (notify_value RX_DONE_BIT) { int rx_len lldesc_get_received_len(s_rx_desc, NULL); if (rx_len 0 rx_len DMA_RX_BUF_SIZE) { ESP_LOGI(TAG, rx_len%d, rx_len); start_tx_dma(s_rx_buf, rx_len); } start_rx_dma(); } if (notify_value TX_DONE_BIT) { ESP_LOGI(TAG, tx done); } } } void app_main(void) { uart_dma_init(); xTaskCreate(dma_echo_task, dma_echo_task, TASK_STACK_SIZE, NULL, 12, s_dma_task_hdl); ESP_LOGI(TAG, UART1 DMA echo started); ESP_LOGI(TAG, TX%d RX%d baud%d, UART_TX_PIN, UART_RX_PIN, UART_BAUD_RATE); }代码较长核心要点初始化 GDMA 通道并连接到 UHCI使用lldesc_t链表管理内存通过中断回调通知任务处理数据