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());        
    }
}

ServoIn.cpp@1:b7cc6da72d09, 2015-04-15 (annotated)

Committer:
jebradshaw
Date:
Wed Apr 15 19:36:40 2015 +0000
Revision:
1:b7cc6da72d09
Parent:
0:98a3b6fbd242
Child:
3:19c8eaf905e9
ServoIn Class Library with invalid pulse detection

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jebradshaw 0:98a3b6fbd242 1 // Uses Timer to read servo pulse on single input pin
jebradshaw 0:98a3b6fbd242 2 // J. Bradshaw 20140925
jebradshaw 0:98a3b6fbd242 3 /* Copyright (c) 2015, jbradshaw (http://mbed.org)
jebradshaw 0:98a3b6fbd242 4 *
jebradshaw 0:98a3b6fbd242 5 * Permission is hereby granted, free of charge, to any person obtaining a copy
jebradshaw 0:98a3b6fbd242 6 * of this software and associated documentation files (the "Software"), to deal
jebradshaw 0:98a3b6fbd242 7 * in the Software without restriction, including without limitation the rights
jebradshaw 0:98a3b6fbd242 8 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
jebradshaw 0:98a3b6fbd242 9 * copies of the Software, and to permit persons to whom the Software is
jebradshaw 0:98a3b6fbd242 10 * furnished to do so, subject to the following conditions:
jebradshaw 0:98a3b6fbd242 11 *
jebradshaw 0:98a3b6fbd242 12 * The above copyright notice and this permission notice shall be included in
jebradshaw 0:98a3b6fbd242 13 * all copies or substantial portions of the Software.
jebradshaw 0:98a3b6fbd242 14 *
jebradshaw 0:98a3b6fbd242 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
jebradshaw 0:98a3b6fbd242 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
jebradshaw 0:98a3b6fbd242 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
jebradshaw 0:98a3b6fbd242 18 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
jebradshaw 0:98a3b6fbd242 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
jebradshaw 0:98a3b6fbd242 20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
jebradshaw 0:98a3b6fbd242 21 * THE SOFTWARE.
jebradshaw 0:98a3b6fbd242 22 *
jebradshaw 0:98a3b6fbd242 23 */
jebradshaw 0:98a3b6fbd242 24 #include "mbed.h"
jebradshaw 0:98a3b6fbd242 25 #include "ServoIn.h"
jebradshaw 0:98a3b6fbd242 26
jebradshaw 0:98a3b6fbd242 27 ServoIn::ServoIn(PinName pin): _interrupt(pin){ // create the InterruptIn on the pin specified to ServoIn
jebradshaw 0:98a3b6fbd242 28 _interrupt.rise(this, &ServoIn::PulseRead); // attach PulseRead function of this ServoIn instance
jebradshaw 0:98a3b6fbd242 29
jebradshaw 1:b7cc6da72d09 30 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015); // the member function, and interval (15ms)
jebradshaw 0:98a3b6fbd242 31 pulseMeasure.start();
jebradshaw 0:98a3b6fbd242 32 _pulseFlag = 0;
jebradshaw 0:98a3b6fbd242 33 servoPulse = 0;
jebradshaw 1:b7cc6da72d09 34 _t_state=0;
jebradshaw 0:98a3b6fbd242 35 }
jebradshaw 0:98a3b6fbd242 36
jebradshaw 0:98a3b6fbd242 37 //function to read the servo pulse duration
jebradshaw 0:98a3b6fbd242 38 void ServoIn::PulseRead() {
jebradshaw 0:98a3b6fbd242 39 if(!_pulseFlag){ //if the flag is low, was waiting for high input interrupt
jebradshaw 0:98a3b6fbd242 40 this->pulseMeasure.reset(); //reset the timer
jebradshaw 0:98a3b6fbd242 41 _interrupt.fall(this, &ServoIn::PulseRead);
jebradshaw 0:98a3b6fbd242 42 _pulseFlag = 1; //set the pulse input flag
jebradshaw 0:98a3b6fbd242 43 }
jebradshaw 0:98a3b6fbd242 44 else{
jebradshaw 0:98a3b6fbd242 45 servoPulse = pulseMeasure.read_us();
jebradshaw 0:98a3b6fbd242 46 _interrupt.rise(this, &ServoIn::PulseRead);
jebradshaw 0:98a3b6fbd242 47 _pulseFlag = 0;
jebradshaw 1:b7cc6da72d09 48 }
jebradshaw 1:b7cc6da72d09 49 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015); //setup interrupt for 15ms
jebradshaw 1:b7cc6da72d09 50 _t_state=0; //re-zero t-state
jebradshaw 0:98a3b6fbd242 51 }
jebradshaw 0:98a3b6fbd242 52
jebradshaw 0:98a3b6fbd242 53
jebradshaw 0:98a3b6fbd242 54 int ServoIn::read(void){
jebradshaw 0:98a3b6fbd242 55 return servoPulse;
jebradshaw 1:b7cc6da72d09 56 }
jebradshaw 1:b7cc6da72d09 57
jebradshaw 1:b7cc6da72d09 58 void ServoIn::timeoutTest(void){
jebradshaw 1:b7cc6da72d09 59 if(!_t_state){
jebradshaw 1:b7cc6da72d09 60 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
jebradshaw 1:b7cc6da72d09 61 _t_state=1; //toggle t_sate (15ms has elapsed without servo edge
jebradshaw 1:b7cc6da72d09 62 }
jebradshaw 1:b7cc6da72d09 63 else{ //30 ms has elapsed without a valid servo pulse
jebradshaw 1:b7cc6da72d09 64 _pulseFlag = 0;
jebradshaw 1:b7cc6da72d09 65 _t_state=0;
jebradshaw 1:b7cc6da72d09 66 servoPulse = 0;
jebradshaw 1:b7cc6da72d09 67 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
jebradshaw 1:b7cc6da72d09 68 }
jebradshaw 1:b7cc6da72d09 69 }
jebradshaw 1:b7cc6da72d09 70