Joseph Bradshaw / ServoIn

Class Library for reading hobby servos and detecting invalid or disconnected channels

Dependents:   MadPulseCntrl Emaxx_Navigation Emaxx_Navigation_Dynamic_HIL Madpulse_Speed_Control_temp ... more

ServoIn Class Library

This class library uses external interrupts with timer functions to read servos pulses on mbed input pins.

ServoIn Library usage example

#include "mbed.h"
#include "ServoIn.h"

DigitalOut led1(LED1);
ServoIn servoIn1(p15);
ServoIn servoIn2(p14);
Serial pc(USBTX, USBRX); // tx, rx

int main() {    
    pc.baud(921600);            //Fast baud rate
        
    while(1) {
        led1 = 1;
        wait(0.05);
        led1 = 0;
        wait(0.05);
        
        pc.printf("servo pulse: CH1=%5dus  CH2=%5dus\r\n", servoIn1.read(), servoIn2.read());        
    }
}

Diff: ServoIn.cpp

Revision:
1:b7cc6da72d09
Parent:
0:98a3b6fbd242
Child:
3:19c8eaf905e9
--- a/ServoIn.cpp	Tue Apr 14 20:05:13 2015 +0000
+++ b/ServoIn.cpp	Wed Apr 15 19:36:40 2015 +0000
@@ -27,9 +27,11 @@
 ServoIn::ServoIn(PinName pin): _interrupt(pin){        // create the InterruptIn on the pin specified to ServoIn
     _interrupt.rise(this, &ServoIn::PulseRead); // attach PulseRead function of this ServoIn instance
 
+    _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015); // the member function, and interval (15ms)
     pulseMeasure.start();
     _pulseFlag = 0;
     servoPulse = 0;
+    _t_state=0;
 }
 
 //function to read the servo pulse duration
@@ -43,10 +45,26 @@
         servoPulse = pulseMeasure.read_us();
         _interrupt.rise(this, &ServoIn::PulseRead);
         _pulseFlag = 0;
-    }    
+    }
+    _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015); //setup interrupt for 15ms
+    _t_state=0;  //re-zero t-state    
 }
 
 
 int ServoIn::read(void){
     return servoPulse;    
-}
\ No newline at end of file
+}
+
+void ServoIn::timeoutTest(void){
+    if(!_t_state){
+        _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
+        _t_state=1;  //toggle t_sate (15ms has elapsed without servo edge
+    }
+    else{   //30 ms has elapsed without a valid servo pulse
+        _pulseFlag = 0;
+        _t_state=0;
+        servoPulse = 0;
+        _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
+    }
+}
+