dsp modubus ASCII协议rs485串口程序例程

以下是一个简单的DSP Modbus ASCII协议的RS485串口程序例程，供参考：

#include "DSP2833x_Device.h"
#include "DSP2833x_Examples.h"

#define UART_TX_PIN GPIO24
#define UART_RX_PIN GPIO25

#define MAX_DATA_LENGTH 64

Uint16 data[MAX_DATA_LENGTH];
Uint16 dataLength;

void init_RS485(void);
void init_UART(void);
void send_RS485(Uint16 *data, Uint16 length);
void receive_RS485(Uint16 *data, Uint16 *length);
void send_UART(Uint16 data);
void receive_UART(Uint16 *data);

void main(void)
{
    init_RS485();
    init_UART();

    while(1)
    {
        receive_RS485(data, &dataLength);

        // process received data

        send_RS485(data, dataLength);
    }
}

void init_RS485(void)
{
    EALLOW;

    GpioCtrlRegs.GPAMUX2.bit.GPIO20 = 0;
    GpioCtrlRegs.GPADIR.bit.GPIO20 = 1;
    GpioDataRegs.GPACLEAR.bit.GPIO20 = 1; // set to receive mode

    GpioCtrlRegs.GPAMUX2.bit.GPIO21 = 0;
    GpioCtrlRegs.GPADIR.bit.GPIO21 = 1;
    GpioDataRegs.GPACLEAR.bit.GPIO21 = 1; // set to receive mode

    EDIS;
}

void init_UART(void)
{
    EALLOW;

    GpioCtrlRegs.GPAMUX2.bit.GPIO24 = 1;
    GpioCtrlRegs.GPADIR.bit.GPIO24 = 1; // set as output

    GpioCtrlRegs.GPAMUX2.bit.GPIO25 = 1;
    GpioCtrlRegs.GPADIR.bit.GPIO25 = 0; // set as input

    SciaRegs.SCICCR.all = 0x0007;   // 1 stop bit,  No loopback 
                                    // No parity,8 char bits, 
                                    // async mode, idle-line protocol
    SciaRegs.SCICTL1.all = 0x0003;  // enable TX, RX, internal SCICLK, 
                                    // Disable RX ERR, SLEEP, TXWAKE
    SciaRegs.SCICTL2.bit.TXINTENA = 0;
    SciaRegs.SCICTL2.bit.RXBKINTENA = 0;
    SciaRegs.SCICTL2.bit.TXEMPTY = 1;

    SciaRegs.SCIHBAUD = 0x0000;
    SciaRegs.SCILBAUD = 0x002E;      // baud rate 9600 @ LSPCLK = 150MHz

    SciaRegs.SCICTL1.all = 0x0023;  // Relinquish SCI from Reset
    SciaRegs.SCIFFTX.all = 0xC000;
    SciaRegs.SCIFFRX.all = 0x0021;

    EDIS;
}

void send_RS485(Uint16 *data, Uint16 length)
{
    Uint16 i;

    EALLOW;

    GpioDataRegs.GPASET.bit.GPIO20 = 1; // set to transmit mode
    GpioDataRegs.GPASET.bit.GPIO21 = 1;

    DELAY_US(100);

    for(i=0; i<length; i++)
    {
        send_UART(data[i]);
    }

    SciaRegs.SCIFFTX.bit.TXFFINTCLR = 1;
    SciaRegs.SCIFFTX.bit.TXFFINT = 1;

    DELAY_US(100);

    GpioDataRegs.GPACLEAR.bit.GPIO20 = 1; // set to receive mode
    GpioDataRegs.GPACLEAR.bit.GPIO21 = 1;

    EDIS;
}

void receive_RS485(Uint16 *data, Uint16 *length)
{
    Uint16 i;

    EALLOW;

    GpioDataRegs.GPASET.bit.GPIO20 = 1; // set to transmit mode
    GpioDataRegs.GPACLEAR.bit.GPIO21 = 1;

    DELAY_US(100);

    GpioDataRegs.GPACLEAR.bit.GPIO20 = 1; // set to receive mode
    GpioDataRegs.GPACLEAR.bit.GPIO21 = 1;

    DELAY_US(100);

    *length = SciaRegs.SCIFFRX.bit.RXFFST;

    for(i=0; i<*length; i++)
    {
        receive_UART(data+i);
    }

    EDIS;
}

void send_UART(Uint16 data)
{
    while(SciaRegs.SCIFFTX.bit.TXFFST != 0) {}

    SciaRegs.SCITXBUF = data;
}

void receive_UART(Uint16 *data)
{
    while(SciaRegs.SCIRXST.bit.RXRDY == 0) {}

    *data = SciaRegs.SCIRXBUF.all;
}

需要注意的是，此程序仅供参考，具体实现需要根据实际情况进行调整和修改。同时，还需要根据Modbus ASCII协议的要求进行数据的读写和校验。