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:
- 3:bf0a5effbed2
- Parent:
- 2:c4d4f0f9d77c
- Child:
- 4:64d9c0bed75b
--- a/main.cpp Sat Jun 01 07:49:57 2013 +0000
+++ b/main.cpp Mon Jun 03 12:36:37 2013 +0000
@@ -2,8 +2,8 @@
//see mbed.org/users/strysd/notebook/measure_humidity_with_hs15p_and_lmc555/
#define ohm_constant 7.2 //if use 0.1 micro F
+#define in_limit 20 //limit of interrupt times
-Serial pc(USBTX, USBRX);
InterruptIn in(p8);
DigitalOut vcc555(p9);
DigitalOut led(LED1);
@@ -12,15 +12,16 @@
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;
+int in_count = 0;//interrupt times
void flip(void)
{
if(in_count > 0){
- t_period = t1.read_us();// Get time since last interrupt
+ if(in_count > 15){
+ t_period = t1.read_us();// Get time since last interrupt
+ }
+ t1.reset();// Reset timer and wait for next interrupt
in_count--;
- t1.reset();// Reset timer and wait for next interrupt
} else {
//No use interrupt
vcc555 = led = 0;
@@ -34,24 +35,28 @@
in.mode(PullUp);
in.rise(&flip);// Set up the interrupt for rising edge
- pc.printf("\rStarting measure\n");
+ printf("\rStarting measure\n");
while (1) {
//Use interrupt
+ t_period = 0;
t1.start();
in_count = in_limit;
vcc555 = led = 1;
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);
+
+ if (t_period < 20 || t_period > 100000){
+ //< 20 micro sec (> 50 kHz)
+ //> 0.1 sec (< 10 Hz)
+ printf("\r not ready\n");
+ wait_ms(5000);
} else {
- pc.printf("\r not ready\n");
+ my_freq = 1000000/t_period;// Convert to Hz
+ my_ohm = t_period * ohm_constant / 1000;// Convert to kilo ohm
+ printf("\r %d Hz, %d micro sec, %4.1f kilo ohm \n",
+ (int)my_freq, (int)t_period, my_ohm);
}
- wait_ms(1800);
+
+ wait_ms(4800);
}
}
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