pulseIn函数工作，PC指针是不是一直在函数内部
本帖最后由 zhixiang 于 2014-7-26 11:41 编辑pulseIn函数工作时，PC指针是不是一直在函数内部，直到电平变化为止，然后跳出函数，运行一个指针命令。，比如高电平持续了3s,那这3s指针一直停留在这里计数，其他的事都坐不了？Arduino不好单步调试，请知道的朋友指点迷津，谢谢 最好的解释就是直接看代码。/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
* or LOW, the type of pulse to measure.Works on pulses from 2-3 microseconds
* to 3 minutes in length, but must be called at least a few dozen microseconds
* before the start of the pulse. */
unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout)
{
// cache the port and bit of the pin in order to speed up the
// pulse width measuring loop and achieve finer resolution.calling
// digitalRead() instead yields much coarser resolution.
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
uint8_t stateMask = (state ? bit : 0);
unsigned long width = 0; // keep initialization out of time critical area
// convert the timeout from microseconds to a number of times through
// the initial loop; it takes 16 clock cycles per iteration.
unsigned long numloops = 0;
unsigned long maxloops = microsecondsToClockCycles(timeout) / 16;
// wait for any previous pulse to end
while ((*portInputRegister(port) & bit) == stateMask)
if (numloops++ == maxloops)
return 0;
// wait for the pulse to start
while ((*portInputRegister(port) & bit) != stateMask)
if (numloops++ == maxloops)
return 0;
// wait for the pulse to stop
while ((*portInputRegister(port) & bit) == stateMask) {
if (numloops++ == maxloops)
return 0;
width++;
}
// convert the reading to microseconds. The loop has been determined
// to be 20 clock cycles long and have about 16 clocks between the edge
// and the start of the loop. There will be some error introduced by
// the interrupt handlers.
return clockCyclesToMicroseconds(width * 21 + 16);
} pathletboy 发表于 2014-7-26 10:07 static/image/common/back.gif
最好的解释就是直接看代码。/* Measures the length (in microseconds) of a pulse on the pin; state is H ...
谢谢你的回复。但是光看这段代码，看不出pulseIn函数的工作模式，在板子上测试，得出运行时，PC指针没有在pulseIn内部停留，包括Mode相符时，计算出的脉冲时间也有一段延时。总体来着，用起来不是很方便。不知道大家用起来怎么样，有什么心得
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