如何发送可变大小的字符串？

大家好！经过长时间的等待，我终于得到了新的MCU，并希望与之通信。我想用UART和DMA发送字符串。我尝试了很多次，但没有发送字符串；只能发送一个字符。如何发送可变大小的字符串？你有什么代码示例吗？P.S.：我不想使用和声。这是我的代码：UART init代码：我使用UART4为UTAR4MY TX函数设置TXDMA0：



      以下为原文

    Hello everybody!
After long waiting, I finally got my new MCU and want to communicate with it.
I want to send string to using UART and DMA. I tried so many times but didnt send strings; I can only send one char.
How can I send variable sized string? Do you have any code example for that?

P.S.: I dont want to use HARMony.

Here is my code:

UART Init Code: I'm Using UART4 for TX

void InitUART(void)
{
    // UART init
    TRISEbits.TRISE0 = 1; // RE0 for RX
    TRISEbits.TRISE1 = 0; // RE1 for TX
    TRISDbits.TRISD8 = 0; // RS485 DIR
   
    IO_UnLock();
   
    U3RXRbits.U3RXR = 0b01100; // RE0 for UART3 RX
    RPE1Rbits.RPE1R = 0b00010; // RE1 for UART4 TX
   
    IO_Lock();
   
    U3MODE = 0x0000;
    U3STAbits.URXEN = 1; // Enable RX
    U3STAbits.UTXEN = 0; // Disable TX
    U3BRG = (PBCLK/(16*BAUD_RATE)) - 1;
   
    U4MODE = 0x0000;
    U4STAbits.URXEN = 0; // Disable RX
    U4STAbits.UTXEN = 1; // Enable TX
    U4BRG = (PBCLK/(16*BAUD_RATE)) - 1;
   
    // Interrupt
    IPC15bits.U3RXIP = 3; // Priority 3
    IPC15bits.U3RXIS = 2; // Sub-Priority 2
            
    IFS2bits.U4TXIF = 0; // Clear the Transmit Interrupt Flag
    IEC2bits.U4TXIE = 0; // Disable Transmit Interrupts
    IFS1bits.U3RXIF = 0; // Clear the Recieve Interrupt Flag
    IEC1bits.U3RXIE = 1; // Enable Recieve Interrupts
   
    U3MODEbits.ON = 1; // Uart3 On
    U4MODEbits.ON = 1; // Uart4 On
   
    InitDMA0();
}

DMA0 Setup for UART4


void InitDMA0(void)
{
IEC2bits.DMA0IE = 0;
IFS2bits.DMA0IF = 0;
DCH0CON = 0x0000;
DCH0ECON = 0x0000;

DCH0CONbits.CHPRI = 3;
DCH0ECONbits.CHSIRQ = _UART4_TX_VECTOR; // IRQ UART4 TX
DCH0ECONbits.SIRQEN = 0; // DMA's interruption disable
DCH0SSA = 1;
DCH0DSA = VirtToPhys((void*)&U4TXREG);
DCH0SSIZ = 300;
DCH0DSIZ = 300; // Destination size 1 bytes
DCH0CSIZ = 300; // 1 bytes transferred per event
DCH0INT = 0; // Any Interruption

DCH0CONbits.CHEN = 0; // Disable DMA channel
}

My TX Function:

unsigned char UART_String(unsigned char *s, unsigned int Length)
{
if(U4STAbits.UTXBF==0)
{
DCH0CONbits.CHEN = 0;

DCH0SSA = KVA_TO_PA(&*s);
DCH0DSA = KVA_TO_PA(&U4TXREG);
DCH0DSIZ = 1;
DCH0CSIZ = 1;
DCH0SSIZ = Length;
DCH0ECONbits.CHSIRQ = _UART4_TX_VECTOR;

if(DCH0ECONbits.CFORCE == 0)
{
DCH0ECONbits.CFORCE = 1;
DCH0CONbits.CHEN = 1;
}
}
}