uart - 我正在寻找示例代码以通过 DMA 而不是中断为 MSP430 上的 USCI (UART) 提供服务

Question

我有通过中断读取 USCI (UART) 的代码“正常”，但 TI SimpliciTI 堆栈是一个 CPU pig ，它在为 radio 提供服务时会丢弃 UART 字节。

我认为 DMA 是可行的方法，但我找不到使用 USCI 作为输入的 DMA 的完整示例。

Answer 1

这就是我最终做的。有用!

struct {
#ifndef USE_DMA
    volatile uint8_t rx_head  ;
#endif
    volatile uint8_t rx_tail  ;
    uint8_t rx_buffer[128];
} uart = { 0,0};


void UART_Init(void) 
{
#ifndef USE_DMA
   uart.rx_head = 0;
#endif
   uart.rx_tail = 0;


  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  PMAPPWD = 0x02D52;                        // Get write-access to port mapping regs
  P1MAP5 = PM_UCA0RXD;                      // Map UCA0RXD output to P1.5
  P1MAP6 = PM_UCA0TXD;                      // Map UCA0TXD output to P1.6
  PMAPPWD = 0;                              // Lock port mapping registers

  P1DIR |= BIT6;                            // Set P1.6 as TX output
  P1SEL |= BIT5 + BIT6;                     // Select P1.5 & P1.6 to UART function

  UCA0CTL1 = UCSWRST;                      // **Put state machine in reset**
 #ifdef UART_9600
  UCA0CTL1 |= UCSSEL_1;                     // CLK = ACLK
  UCA0BR0 = 0x03;                           // 32kHz/9600=3.41 (see User's Guide)
  UCA0BR1 = 0x00;                           //
  UCA0MCTL = UCBRS_3+UCBRF_0;               // Modulation UCBRSx=3, UCBRFx=0
 #elif defined(UART_9600_SMCLK)
  UCA0CTL1 |= UCSSEL_2;                     // SMCLK
  UCA0BR0 = 0xE2;                           // 12MHz/12500
  UCA0BR1 = 0x04;                           //
  UCA0MCTL = UCBRS_2+UCBRF_0;               // Modulation UCBRSx=3, UCBRFx=0
 #elif defined(UART_115200)
  UCA0CTL1 |= UCSSEL_2;                     // SMCLK
  UCA0BR0 = 104;                            // 12MHz/115200
  UCA0BR1 = 0;                              //
  UCA0MCTL = UCBRS_1 + UCBRF_0;            // Modulation UCBRSx=1, UCBRFx=0
 #else
 #error Please select one of the supported baudrates.
#endif
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**

#ifdef USE_DMA
  memset(uart.rx_buffer,0,sizeof(uart.rx_buffer));
  DMACTL0 = DMA0TSEL_16;               // USCIA0 RX trigger
  DMA0SAL = (uint16_t)  &UCA0RXBUF;    // Source address
  DMA0DAL = (uint16_t) uart.rx_buffer; // Destination address
  DMA0SZ = sizeof(uart.rx_buffer);     // Block size. this counts down to 0, then reloads.
  DMA0CTL = DMADSTINCR_3 + DMASBDB + DMADT_4 + DMALEVEL;
  DMA0CTL |= DMAEN;
#else
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt
#endif
}


int UART_GetChar(void)
{
#ifdef USE_DMA
  if (DMA0SZ + uart.rx_tail != sizeof(uart.rx_buffer))
#else
  if  (  uart.rx_head != uart.rx_tail )
#endif
    {
      int c;
      c = uart.rx_buffer[uart.rx_tail];
      uint8_t next = uart.rx_tail + 1;
      if (next >= sizeof(uart.rx_buffer)) next = 0;
      uart.rx_tail = next;
      return c;
    }

return -1;
}