Satoru Yoshida
test interruptIn feature with 555 timer
Dependencies: ClockControl PowerControl mbed
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Frequency_counter
by 
Satoru Yoshida
Test interruptIn function with using LMC555 timer IC
LPC 1768 自身が持つタイマー割り込み機能を使わずに、 あえて外部のタイマー IC 555 からの信号で周期的に割り込みするテスト。
下記の回路例では、555 の output 端子が 約 10 秒周期のうち、0.3 秒間 Low になるはず。 ただし、コンデンサーおよび抵抗の誤差の影響があり、実測値は約７秒周期
C を 47μ から 330 μ に変えると約１分前後で周期的に割り込みがかかります。
なるべく配線が交差しないように部品配置してみた例
Diff: main.cpp
- Revision:
- 1:e2034bcdb101
- Parent:
- 0:c5bcf643a8b1
- Child:
- 2:c4d4f0f9d77c
--- a/main.cpp Sun Feb 03 21:06:02 2013 +0000
+++ b/main.cpp Sat Jun 01 05:44:10 2013 +0000
@@ -1,32 +1,59 @@
#include "mbed.h"
+//see mbed.org/users/strysd/notebook/measure_humidity_with_hs15p_and_lmc555/
+#define ohm_constant 7.2 //if use 0.1 micro F
+
Serial pc(USBTX, USBRX);
InterruptIn in(p8);
+DigitalOut vcc555(p9);
DigitalOut led(LED1);
-DigitalOut led2(LED2);
Timer t1;
-float t_period = 0; // This is the period between interrupts in microseconds
-float t_freq = 0;
+float t_period = 0;//between interrupts in microseconds
+float my_freq = 0;//Hz
+float my_ohm = 0;//ohm for HS15P
+int in_limit = 10;
+int in_count = 0;
void flip(void)
{
- led=!led;
- t_period = t1.read_us(); // Get time since last interrupt
- t_freq = (1/t_period)*1000000; // Convert period (in us) to frequency (Hz)
- t1.reset(); // Reset timer and wait for next interrupt
+ if(in_count > 0){
+ t_period = t1.read_us();// Get time since last interrupt
+ in_count--;
+ t1.reset();// Reset timer and wait for next interrupt
+ } else {
+ //No use interrupt
+ in.mode(PullDown);
+ vcc555 = led = 0;
+ t1.stop();
+ }
}
+
int main() {
- pc.printf("\rStarting frequency counter\n");
- in.mode(PullDown); // Set the pin to Pull Down mode.
- in.rise(&flip); // Set up the interrupt for rising edge
- t1.start(); // start the timer
+ vcc555 = led = 0;
+ in.rise(&flip);// Set up the interrupt for rising edge
+ in.mode(PullDown);
+
+ pc.printf("\rStarting measure\n");
while (1) {
- wait_ms(100);
- led2=!led2;
- pc.printf("\rfrq is %d Hz\n", (int)t_freq);
+ //Use interrupt
+ t1.start();
+ in_count = in_limit;
+ vcc555 = led = 1;
+ in.mode(PullUp);
+ wait_ms(200);
+
+ if (t_period > 0){
+ my_freq = (1000/t_period)*1000; // Convert to Hz
+ my_ohm = t_period * ohm_constant;// Convert to ohm
+
+ pc.printf("\r %d Hz, %d micro sec, %d ohm \n",
+ (int)my_freq, (int)t_period, (int)my_ohm);
+ } else {
+ pc.printf("\r not ready\n");
+ }
+ wait_ms(1800);
}
-
}
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