AT91sam7x 256：仅中断运行一次

Question

我在 at91sam7x256 上使用带 DMA 的 USART 读取和写入数据。因为我没有成功，所以我开始创建一个简单的例子，但问题已经存在。主要问题是中断例程第一次触发，第一次后我无法从 USART 接收数据！

#include "at91sam7x256.h"

char            Buffer[10];             // holds received characters
unsigned long   nChars = 0;             // counts number of received chars
char            *pBuffer = &Buffer[0];  // pointer into Buffer

void Usart0IrqHandler (void);
void USART0Setup(void);

int main(void)
{
    unsigned long   j;
    unsigned int    IdleCount = 0;

    // set up USART0
    USART0Setup();

    // *****************************
    // *  endless blink loop       *
    // *****************************
    while (1) {
        for (j = 1000000; j != 0; j-- );                // wait 1 second 1000000

        IdleCount++;                                    // count # of times through the idle loop

        for (j = 1000000; j != 0; j-- );                // wait 1 second 1000000
    }

}
////////



 void Usart0IrqHandler (void) {
    volatile AT91PS_USART pUsart0 = AT91C_BASE_US0; // create a pointer to USART0 structure
    if ((pUsart0->US_CSR & AT91C_US_ENDRX) == AT91C_US_ENDRX) {
        // we have a end-of-receive interrupt (ENDRX)
        pUsart0->US_RCR = 10; // restore the receive count - clears ENDRX flag
    }
}


void USART0Setup(void) {
    volatile AT91PS_USART pUSART0 = AT91C_BASE_US0;     // create a pointer to USART0 structure
    volatile AT91PS_AIC pAIC = AT91C_BASE_AIC;          // pointer to AIC data structure
    volatile AT91PS_PIO pPIO = AT91C_BASE_PIOA;         // pointer to PIO data structure

    volatile AT91PS_PMC pPMC = AT91C_BASE_PMC;          // pointer to PMC data structure
    pPMC->PMC_PCER = (1<<AT91C_ID_US0);                 // enable usart0 peripheral clock
    pPIO->PIO_PDR = AT91C_PA0_RXD0 | AT91C_PA1_TXD0;    // enable peripheral control of PA0 and PA1 (RXD0 and TXD0)
    pPIO->PIO_ASR = AT91C_PIO_PA0 | AT91C_PIO_PA1;      // assigns the 2 I/O lines to peripheral A function
    pPIO->PIO_BSR = 0;                                  // peripheral B function set to "no effect"

    pUSART0->US_CR =    AT91C_US_RSTRX |        // reset receiver   
                        AT91C_US_RSTTX |        // reset transmitter
                        AT91C_US_RXDIS |        // disable receiver
                        AT91C_US_TXDIS;         // disable transmitter

    pUSART0->US_MR =    AT91C_US_PAR_NONE |     // no parity
                        0x3 << 6;               // 8-bit characters

    pUSART0->US_IER = 0x00;                     // no usart0 interrupts enabled  (no effect) 
    pUSART0->US_IDR = 0xFFFF;                   // disable all USART0 interrupts

    pUSART0->US_BRGR = 0x139;       // CD = 0x139  (313 from above calculation for 9600 baud)  
                                    // FP=0 (not used)

    pUSART0->US_RTOR = 0;                       // receiver time-out (disabled)

    pUSART0->US_TTGR = 0;                       // transmitter timeguard (disabled)

    pUSART0->US_RPR = (unsigned int)Buffer;     // address of DMA input buffer

    pUSART0->US_RCR = 10;                       // we'll read in 10 chars via DMA

    pUSART0->US_TPR = (unsigned int)0;          // address of DMA output buffer (use same one)

    pUSART0->US_TCR = 0;                        // we'll transmit 0 chars via DMA

    pUSART0->US_RNPR = (unsigned int)0;         // next DMA receive buffer address
                                                // if set to zero, it is not used

    pUSART0->US_RNCR = (unsigned int)0;         // next DMA receive counter
                                                // if set to zero, it is not used

    pUSART0->US_TNPR = (unsigned int)0;         // next DMA transmit buffer address
                                                // if set to zero, it is not used

    pUSART0->US_TNCR = (unsigned int)0;         // next DMA transmit counter
                                                // if set to zero, it is not used

    pUSART0->US_PTCR =  AT91C_PDC_RXTEN |   // enable receive transfer,
                        AT91C_PDC_TXTDIS;   // disable transmit transfer

    // Disable USART0 interrupt in AIC Interrupt Disable Command Register
    pAIC->AIC_IDCR = (1<<AT91C_ID_US0);                 
    // Set the USART0 IRQ handler address in AIC Source 
    pAIC->AIC_SVR[AT91C_ID_US0] =                       
        (unsigned int)Usart0IrqHandler;                 // Vector Register[6]
    // Set the interrupt source type and priority 
    pAIC->AIC_SMR[AT91C_ID_US0] =                       
        (AT91C_AIC_SRCTYPE_INT_HIGH_LEVEL | 0x4 );      // in AIC Source Mode Register[6]
    // Enable the USART0 interrupt in AIC Interrupt Enable Command Register
    pAIC->AIC_IECR = (1<<AT91C_ID_US0);                 

    // enable the USART0 receiver and transmitter
    pUSART0->US_CR = AT91C_US_RXEN | AT91C_US_TXEN;

    // enable the USART0 end-of-receive interrupt
    pUSART0->US_IER = AT91C_US_ENDRX;                   // enable ENDRX usart0 end-of-receive interrupt
    pUSART0->US_IDR = ~AT91C_US_ENDRX;                  // disable all interrupts except ENDRX

}

//------------------
// end of file
//------------------

Answer 1

在中断中设置计数(US_RCR)之前，需要重新初始化接收指针：

pUSART0->US_RPR = (unsigned int)Buffer;

您的设备可能出现故障，因为 PDC 正在缓冲区外写入。

Answer 2

有两个问题：
1- 当我使用 Keil uVision 时，我需要使用 __irq 来定义中断服务程序！
2-令人惊讶的是，中断的结束没有被触发！所以使用： *AT91C_AIC_EOICR = 0;

void __irq Usart0IrqHandler (void) {    
volatile AT91PS_USART pUsart0 = AT91C_BASE_US0; // create a pointer to USART0 structure
    if ((pUsart0->US_CSR & AT91C_US_ENDRX) == AT91C_US_ENDRX) {
        pUsart0->US_RPR = (unsigned int)Buffer; // we have a end-of-receive interrupt (ENDRX)
        pUsart0->US_RCR = 10;                   // restore the receive count - clears ENDRX flag
    }
       *AT91C_AIC_EOICR = 0;                    // end of interrupts
}

AT91sam7x 256：仅中断运行一次

AT91sam7x 256: Interrupt just run once

c

embedded

arm

interrupt

keil

AT91sam7x 256：仅中断 运行 一次

AT91sam7x 256: Interrupt just run once

c

embedded

arm

interrupt

keil

AT91sam7x 256：仅中断运行一次