输入捕获“慢”频率

使用32位捕获模式来正确处理较低的输入频率。



      以下为原文

    Use a 32-bit capture mode to correctly handle the lower input frequencies.

嗨，是的，你的理解主要是正确的。为了测量长周期信号，你可以安排处理来自定时器（TMR3）和捕获模块的中断。如果在中断CP之前发生定时器中断，在32位整数变量UIT32 32中添加65536，清除中断标志和LE。当中断捕获发生时，将捕获寄存器的值添加到上述变量中，也可以将捕获寄存器值存储在单独的16位无符号变量UUT1616中，用作下一个间隔的开始时间。这样，你可以精确地捕捉每一个脉冲，而不必重置计时器。周期时间计算可能是这样的：间隔＝（CopTraceEndo-CopTrimeRead）+（TimeRyLoop**xx10000）；然后用无符号整数类型变量进行计时器和捕获值的计算，然后Calc。即使在一段时间内定时器翻转到零时，被调整的间隔也可以是正确的。或者，这些设备具有定时器和输入捕获，可以安排在32位模式下一起工作，参见寄存器ICXCON2 IC32位的数据表，以及寄存器TXCON-T32位。迈西尔



      以下为原文

    Hi,
Yes, you understanding is mostly correct.
 
To measure long period signals,
you may arrange to handle interrupts from both the timer (TMR3)  and the capture module.
If interrupt from Timer happen before interrupt from CP, add 65536 in a 32 bit integer variable, uint32_t,
clear the interrupt flag and leave the interrupt handler.
When Capture interrupt happen, add value of capture register to the variable mentioned above.
 
You may also store the capture register value in a separate 16 bit unsigned variable, uint16_t
to use as start time for the next interval. This way, you may capture every pulse precisely, without having to reset the Timer.
Period time calculation may be something like this:
Interval =  (Capture_End - Capture_Previous) + (timer_cycles * 0x10000);
 
Do all calculations of timer and capture values with unsigned integer type variables,
then calculated intervals may be correct even when timer roll around to zero during a period.
 
Alternatively,
These devices have Timers and Input Capture, that may be arranged to work together in 32 bit mode,
See Datasheet about Register ICxCON2   IC32 bit,
and   Register TxCON  T32 bit.
 
   Mysil

一个32位定时器（例如级联T2+T3）在捕获模式下使用16 MHz时钟（FCY）在大约268秒（4min 28秒）后翻滚。作为上升沿上的一个输入捕获，它将给你一个分辨率为62.5纳秒的周期时间。我在输入捕获中使用一个GPS PPS脉冲来确定我的CPU时钟偏离16兆赫，这样我就可以计算出输出脉冲的周期时间。我在输出比较模式中使用这个来产生非常精确的输出脉冲。



      以下为原文

    A 32 bit timer (for example concatenate T2+T3) in capture mode using a 16 MHz clock (FCY) rolls over after approximately 268 seconds (4min 28s). Used as an input capture on the rising edge it will give you the period time with a resolution of 62.5 ns.
I use a GPS PPS pulse in Input Capture to determine my CPU clock's deviation from 16 MHz so I can calculate the period time of an output pulse with the accuracy of the crystal taken out of the picture.
I use this in Output Compare mode to generate extremely accurate output pulses.

你不需要重置计时器。让它自由运行，然后减去连续捕获。如果测得的间隔小于定时器周期，则得到正确的结果。只需确保使用无符号变量.& lt；Edg＆Gt；此外，如果您知道间隔不能小于某个阈值，那么通过这样做，您可以扩展您的捕获范围，甚至超过定时器周期。



      以下为原文

   


You do not need to reset the timer. Let it free run. Then subtract the consecutive captures. If the interval being measured is less than the timer period, you'll get the correct result. Just make sure you use unsigned variables.
 
Moreover, if you know that the interval cannot be less than a certain threshold then you can extend your capture range even past the timer period, by doing this:
 
if (captured_value < threshold) captured_value += timer_period;