標(biāo)題: STM32學(xué)習(xí)之一 - 計(jì)頻器設(shè)計(jì)原理 [打印本頁(yè)]
作者: lizi 時(shí)間: 2014-8-29 17:22
標(biāo)題: STM32學(xué)習(xí)之一 - 計(jì)頻器設(shè)計(jì)原理
檢測(cè)外部脈沖信號(hào)頻率方法有三種：
(1) TIM3 is configured in Input Capture Mode: the external signal is connected to
TIM3 Channel2 used as input pin.
To measure the frequency we use the TIM3 CC2 interrupt request,
so In the TIM3_IRQHandler routine, the frequency of the external signal is computed.
The "TIM3Freq" variable contains the external signal frequency:
TIM3Freq = TIM3 counter clock / Capture in Hz,
where the Capture is the difference between two consecutive TIM3 captures.
For Low-density, Medium-density, High-density and Connectivity line devices,
the minimum frequency value to measure is 1100 Hz.
For Low-Density Value line, Medium-Density and High-Density Value line devices,
the minimum frequency value to measure is 366 Hz.
(2) TIM3 is configured in PWM Input Mode: the external signal is connected to
TIM3 Channel2 used as input pin.
To measure the frequency and the duty cycle we use the TIM3 CC2 interrupt request,
so In the TIM3_IRQHandler routine, the frequency and the duty cycle of the external
signal are computed.
The "Frequency" variable contains the external signal frequency:
Frequency = TIM3 counter clock / TIM3_CCR2 in Hz,
The "DutyCycle" variable contains the external signal duty cycle:
DutyCycle = (TIM3_CCR1*100)/(TIM3_CCR2) in %.
For Low-density, Medium-density, High-density and Connectivity line devices,
the minimum frequency value to measure is 1100 Hz.
For Low-Density Value line and Medium-Density Value line devices, the minimum
frequency value to measure is 366 Hz.
（3）對(duì)于High-density devices（大容量型）如果檢測(cè)脈沖的頻率小于1100Hz，我們可以采用外部中斷邊沿的觸發(fā)方式來(lái)計(jì)算脈沖的個(gè)數(shù)，通過(guò)定時(shí)器準(zhǔn)確定時(shí)1s所測(cè)得的脈沖個(gè)數(shù)即為脈沖信號(hào)周期。
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