TI中文支持网参考倒程"msp430g2xx3_uscia0_spi_10.c"写了以下SPI通信程序，单片机作为从设备，主设备是以“字”的形式来读取信息。
设计应该是04 06 08 依次发出,但实际观察到单片机发送的是两个相同的字节。如：04 04 06 06或06 06 08 08。这是什么原因呢？
#include <msp430.h>
/**
* main.c
*/
int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
// while (!(P1IN & BIT4)); // If clock sig from mstr stays low,
// it is not yet in SPI mode
P1SEL = BIT1 + BIT2 + BIT4;
P1SEL2 = BIT1 + BIT2 + BIT4;
UCA0CTL1 = UCSWRST; // **Put state machine in reset**
UCA0CTL0 |= UCCKPL + UCMSB + UCSYNC; // 3-pin, 8-bit SPI master
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
IE2 |= UCA0RXIE; // Enable USCI0 RX interrupt
__bis_SR_register(LPM4_bits + GIE); // Enter LPM4, enable interrupts
}
// Echo character
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCIAB0RX_VECTOR
__interrupt void USCI0RX_ISR (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCIAB0RX_VECTOR))) USCI0RX_ISR (void)
#else
#error Compiler not supported!
#endif
{
while (!(IFG2 & UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = 0x04;
while (!(IFG2 & UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = 0x06;
while (!(IFG2 & UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = 0x08;
}
灰小子：
回复 Sheldon He:
我这里测试这个例程也没问题
Delta：
回复 灰小子:
那就是也要观察主机的输出波形,可能是地址段数据格式不同.
下面是波形图,
通道1：从机发送数据；
通道2：主机发送数据；
通道3：主机CS
通道4：主机时钟
第一第二的图就是上述程序的结果,也就是可能两个运行结果:
下面第三图是程序改成延时做间隔做对比,现在主机收到的数据是0B0B6204.
int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
P1DIR &= 0xC3;
P1REN |= 0x20; // P1.5 pullup
P1IE |= 0x20; // P1.5 interrupt enabled
P1IES |= 0x20; // P1.5 Hi/lo edge
P1IFG &= ~0x20; // P1.5 IFG cleared
// while (!(P1IN & BIT4)); // If clock sig from mstr stays low,
// it is not yet in SPI mode
P1SEL = BIT1 + BIT2 + BIT4;
P1SEL2 = BIT1 + BIT2 + BIT4;
UCA0CTL1 = UCSWRST; // **Put state machine in reset**
UCA0CTL0 |= UCCKPL + UCMSB + UCSYNC; // 3-pin, 8-bit SPI master
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
//IE2 |= UCA0RXIE; // Enable USCI0 RX interrupt
__bis_SR_register(LPM3_bits + GIE); // Enter LPM4, enable interrupts
}
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
UCA0TXBUF = 0x62;
__delay_cycles(10);
UCA0TXBUF = 0x04;
__delay_cycles(10);
UCA0TXBUF = 0x0B;
__bis_SR_register(LPM3_bits + GIE); // Enter LPM4, enable interrupts
}
