DMA 串口

串口DMA发送失败，接收没问题

发布于 2025-08-08 16:11:17 浏览：35 订阅该版

我想使用DMA发送，但是出现了发送不出去，但是发送完成回调函数它是能进去的，打印出里面的内容，接收数据是没问题，这是为什么呢？有大佬指点一下吗
```c
#include <rtthread.h>
#include <rtdbg.h>
#include <drivers/pin.h>
#include <drv_common.h>
#include <rtdevice.h>    // 包含 RT-Thread 设备驱动相关定义
#include <drv_usart.h>    // 包含 GPIO 驱动相关定义
/* 根据实际485串口来修改 */
#define SAMPLE_UART_NAME       "uart6"
#define BUFFER_SIZE            1024
#define COMMAND_RSP_TIMEOUT    4

#define RS485_WP_PIN
#ifdef  RS485_WP_PIN
#define RS485_WP    GET_PIN(C, 8)
#define RS485_TX    rt_pin_write(RS485_WP, PIN_HIGH)
#define RS485_RX    rt_pin_write(RS485_WP, PIN_LOW)
#endif
extern rt_ssize_t stm32_dma_transmit(struct rt_serial_device *serial, rt_uint8_t *buf, rt_size_t size, int direction);
extern void stm32_dma_config(struct rt_serial_device *serial, rt_ubase_t flag);
static struct rt_mutex data_mutex;

static rt_device_t modbus_device;
#define SAMPLE_UART_NAME       "uart6"      /* 串口设备名称 */

/* 串口设备句柄 */
static rt_device_t serial;
static uint16_t g_usUART6_RX_LEN = 0;                       // 缓冲区索引
static rt_uint8_t g_ucUART6_RX_BUF[BUFFER_SIZE];           // 接收缓冲区

/* 消息队列控制块 */
static struct rt_messagequeue rx_mq;

struct rx_msg
{
    rt_device_t dev;
    rt_size_t size;
};

void modbus_uart_send(uint8_t *buf,uint16_t len)
{
    RS485_TX;
    rt_device_write(serial, 0, buf, len);
    RS485_RX;
}

/* 接收数据回调函数 */
static rt_err_t uart_input(rt_device_t dev, rt_size_t size)
{
    struct rx_msg msg;
    rt_err_t result;
    msg.dev = dev;
    msg.size = size;

result = rt_mq_send(&rx_mq, &msg, sizeof(msg));
    if ( result == -RT_EFULL)
    {
        /* 消息队列满 */
        rt_kprintf("message queue full！\n");
    }
    return result;
}

/* 发送数据回调函数 */
static rt_err_t uart_tx_done(rt_device_t dev, void *buffer)
{
        /* 消息队列满 */
        rt_kprintf("send complete！\n");
}
static void serial_thread_entry(void *parameter)
{
    struct rx_msg msg;
    rt_err_t result;

while (1)
    {
        rt_memset(&msg, 0, sizeof(msg));
        /* 从消息队列中读取消息*/
        result = rt_mq_recv(&rx_mq, &msg, sizeof(msg), RT_WAITING_FOREVER);
        if (result > 0)
        {
            /* 从串口读取数据*/
            g_usUART6_RX_LEN = rt_device_read(msg.dev, 0, g_ucUART6_RX_BUF, msg.size);
			rt_kprintf("%d\r\n",g_usUART6_RX_LEN);
						RS485_TX;
            /* 通过串口设备 serial 输出读取到的消息 */
            rt_device_write(serial, 0, g_ucUART6_RX_BUF,g_usUART6_RX_LEN);
				RS485_RX;
        }
    }
}

// 初始化函数
int uart_sample() {

rt_err_t ret = RT_EOK;
	struct serial_configure config = RT_SERIAL_CONFIG_DEFAULT;  /* 初始化配置参数 */
#ifdef RS485_WP_PIN
    rt_pin_mode(RS485_WP, PIN_MODE_OUTPUT);
#endif
    char str[] = "hello RT-Thread!\r\n";
    static char msg_pool[256];
    /* 查找串口设备 */
    serial = rt_device_find(SAMPLE_UART_NAME);
    if (!serial)
    {
        rt_kprintf("find %s failed!\n", SAMPLE_UART_NAME);
        return RT_ERROR;
    }

/* 初始化消息队列 */
    rt_mq_init(&rx_mq, "rx_mq", msg_pool, /* 存放消息的缓冲区 */
    sizeof(struct rx_msg), /* 一条消息的最大长度 */
    sizeof(msg_pool), /* 存放消息的缓冲区大小 */
    RT_IPC_FLAG_FIFO); /* 如果有多个线程等待，按照先来先得到的方法分配消息 */
    /* step2：修改串口配置参数 */
    config.baud_rate = BAUD_RATE_115200;      //修改波特率为 9600
    config.data_bits = DATA_BITS_8;           //数据位 8
    config.stop_bits = STOP_BITS_1;           //停止位 1
    config.bufsz     = 512;                   //修改缓冲区 buff size 为 128
    config.parity    = PARITY_NONE;           //无奇偶校验位

/* step3：控制串口设备。通过控制接口传入命令控制字，与控制参数 */
    rt_device_control(serial, RT_DEVICE_CTRL_CONFIG, &config);
    /* 以 DMA 接收及轮询发送方式打开串口设备 */
    rt_device_open(serial, RT_DEVICE_FLAG_DMA_RX | RT_DEVICE_FLAG_DMA_TX | RT_DEVICE_FLAG_RDWR);
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(serial, uart_input);

/* 发送字符串 */
	RS485_TX;
    rt_device_write(serial, 0, str, (sizeof(str) - 1));
	RS485_RX;
	rt_device_set_tx_complete(serial,uart_tx_done);
    /* 创建 serial 线程 */
    rt_thread_t thread = rt_thread_create("serial", serial_thread_entry, RT_NULL, 1024, 25, 10);
    /* 创建成功则启动线程 */
    if (thread != RT_NULL)
    {
        rt_thread_startup(thread);
    }
    else
    {
        ret = RT_ERROR;
    }
}
INIT_APP_EXPORT(uart_sample);
```