串口1234使用问题

发布于 2017-04-17 10:42:17 浏览：3652 订阅该版

使用的是RTT 2.1.0，开启了4个串口。串口1,2 3都是接设备，调试发现，串口在线程中初始化后，发送时，第一个字节掉了，用串口助手看第一个字节没有收到，后面都是正常 的，请问下为什么。
用的命令和MODBUS上面修改的。
```
/* ----------------------- Start implementation -----------------------------*/
BOOL xMBPortSerialInit(UCHAR ucPORT, ULONG ulBaudRate, UCHAR ucDataBits,
        eMBParity eParity)
{
    /**
     * set 485 mode receive and transmit control IO
     * @note MODBUS_SLAVE_RT_CONTROL_PIN_INDEX need be defined by user
     */
    rt_pin_mode(MODBUS_SLAVE_RT_CONTROL_PIN_INDEX, PIN_MODE_OUTPUT);

/* set serial name */
    if (ucPORT == 1) {
#if defined(RT_USING_UART1) || defined(RT_USING_REMAP_UART1)
        extern struct rt_serial_device serial1;
        serial = &serial1;
#endif
    } else if (ucPORT == 2) {
#if defined(RT_USING_UART2)
        extern struct rt_serial_device serial2;
        serial = &serial2;
#endif
    } else if (ucPORT == 3) {
#if defined(RT_USING_UART3)
        extern struct rt_serial_device serial3;
        serial = &serial3;
#endif
    }
    /* set serial configure parameter */
    serial->config.baud_rate = ulBaudRate;
    serial->config.stop_bits = STOP_BITS_1;
    switch(eParity){
    case MB_PAR_NONE: {
        serial->config.data_bits = DATA_BITS_8;
        serial->config.parity = PARITY_NONE;
        break;
    }
    case MB_PAR_ODD: {
        serial->config.data_bits = DATA_BITS_9;
        serial->config.parity = PARITY_ODD;
        break;
    }
    case MB_PAR_EVEN: {
        serial->config.data_bits = DATA_BITS_9;
        serial->config.parity = PARITY_EVEN;
        break;
    }
    }
    /* set serial configure */
    serial->ops->configure(serial, &(serial->config));

/* open serial device */
    if (!serial->parent.open(&serial->parent,
            RT_DEVICE_OFLAG_RDWR | RT_DEVICE_FLAG_INT_RX )) {
        serial->parent.rx_indicate = serial_rx_ind;
    } else {
        return FALSE;
    }

/* software initialize */
    rt_thread_init(&thread_serial_soft_trans_irq,
                   "slave trans",
                   serial_soft_trans_irq,
                   RT_NULL,
                   serial_soft_trans_irq_stack,
                   sizeof(serial_soft_trans_irq_stack),
                   10, 5);
    rt_thread_startup(&thread_serial_soft_trans_irq);
    rt_event_init(&event_serial, "slave event", RT_IPC_FLAG_PRIO);

return TRUE;
}
```
在这个基础上修改的。
发送和读是这么写的

serial->parent.write(&(serial->parent), 0, &ucByte, len);

serial->parent.read(&(serial->parent), 0, pucByte, len);

现在就是第一个字符收不到，搞的我读取配置有时不正常，要读多次。后面都正常，就开机第一个字符没了。