Question

所以，我正在使用Atmega128rfa1板，我的结果很奇怪。

我的代码使用MAC符号计数器。它使用手动信标时间戳。在我的代码中，发生以下情况，PORT_RADIOTIMER_WIDTH是uint32_t的宏：

....
*((PORT_RADIOTIMER_WIDTH *)(&SCOCR2LL)) = 0;
SCOCR2LL = 0;   //set compare registers

*((PORT_RADIOTIMER_WIDTH *)(&SCBTSRLL)) = 0;
SCBTSRLL = 0;   //set compare registers

SCCNTHH = SCCNTHL = SCCNTLH = 0;
SCCNTLL = 0;    // reset timer value

radiotimer_setPeriod(period);   //set period


SCCR0 |= (1 << SCMBTS); // "reset" radiotimer

在此之后，我立即尝试使用以下代码获取自时间戳以来的相对时间：

    PORT_RADIOTIMER_WIDTH count_time = (uint8_t) SCCNTLL;
count_time |= (uint8_t)SCCNTLH << 8;
count_time |= (uint8_t)SCCNTHL << 16;
count_time |= (uint8_t)SCCNTHH << 24;

PORT_RADIOTIMER_WIDTH beacon_time2;
beacon_time2 = (uint8_t) SCBTSRLL;
beacon_time2 |= (uint8_t)SCBTSRLH << 8;
beacon_time2 |= (uint8_t)SCBTSRHL << 16;
beacon_time2 |= (uint8_t)SCBTSRHH << 24;
PORT_RADIOTIMER_WIDTH beacon_time = (uint16_t)beacon_time2;
PORT_RADIOTIMER_WIDTH captured_time = count_time - beacon_time;
print_debug("radiotimer_getCapturedTime count_time %lu or %u\n", count_time);
print_debug("radiotimer_getCapturedTime beacon_time %lu  or %u\n", beacon_time);
print_debug("radiotimer_getCapturedTime captured_time %lu  or %u\n",captured_time);

印刷的是：

radiotimer_getCapturedTime count_time 859 or 859
radiotimer_getCapturedTime beacon_time 7090  or 859
radiotimer_getCapturedTime captured_time 4294961065  or 859

与预期相反，信标时间与count_time大致不同，只是在作为unsigned int进行比较时，而不是作为unsigned long int。怎么了？我对这一点感到非常惊讶。

Answer 1

print_debug()语句看起来很可疑。格式需要两个变量，但您只提供一个变量。每次调用中打印的859可能来自您不期望的变量。

否则，ul版本中的算法是正确的。 859 - 7090在32位无符号算术中等于4294961065。

尝试类似：

print_debug("radiotimer_getCapturedTime count_time %lu or %u\n", count_time, count_time);
print_debug("radiotimer_getCapturedTime beacon_time %lu  or %u\n", beacon_time, beacon_time);
print_debug("radiotimer_getCapturedTime captured_time %lu  or %u\n",captured_time, captured_time);

并查看16位情况下结果是否仍然相同。

AVR / Atmega128rfa1：读取寄存器会产生不同的结果

1 个答案: