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@3:19c8eaf905e9, 2015-05-21 (annotated)

Committer:
jebradshaw
Date:
Thu May 21 18:40:06 2015 +0000
Revision:
3:19c8eaf905e9
Parent:
1:b7cc6da72d09
Child:
4:379f9ab5cb4b
Tests for reading calibrated pulse within range or returns (float)0.0.

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 3:19c8eaf905e9 34 servoPulseMax = 2100;
jebradshaw 3:19c8eaf905e9 35 servoPulseMin = 900;
jebradshaw 3:19c8eaf905e9 36 _t_state=0;
jebradshaw 0:98a3b6fbd242 37 }
jebradshaw 0:98a3b6fbd242 38
jebradshaw 0:98a3b6fbd242 39 //function to read the servo pulse duration
jebradshaw 0:98a3b6fbd242 40 void ServoIn::PulseRead() {
jebradshaw 0:98a3b6fbd242 41 if(!_pulseFlag){ //if the flag is low, was waiting for high input interrupt
jebradshaw 0:98a3b6fbd242 42 this->pulseMeasure.reset(); //reset the timer
jebradshaw 0:98a3b6fbd242 43 _interrupt.fall(this, &ServoIn::PulseRead);
jebradshaw 0:98a3b6fbd242 44 _pulseFlag = 1; //set the pulse input flag
jebradshaw 0:98a3b6fbd242 45 }
jebradshaw 0:98a3b6fbd242 46 else{
jebradshaw 0:98a3b6fbd242 47 servoPulse = pulseMeasure.read_us();
jebradshaw 0:98a3b6fbd242 48 _interrupt.rise(this, &ServoIn::PulseRead);
jebradshaw 0:98a3b6fbd242 49 _pulseFlag = 0;
jebradshaw 1:b7cc6da72d09 50 }
jebradshaw 1:b7cc6da72d09 51 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015); //setup interrupt for 15ms
jebradshaw 1:b7cc6da72d09 52 _t_state=0; //re-zero t-state
jebradshaw 0:98a3b6fbd242 53 }
jebradshaw 0:98a3b6fbd242 54
jebradshaw 0:98a3b6fbd242 55
jebradshaw 0:98a3b6fbd242 56 int ServoIn::read(void){
jebradshaw 0:98a3b6fbd242 57 return servoPulse;
jebradshaw 1:b7cc6da72d09 58 }
jebradshaw 1:b7cc6da72d09 59
jebradshaw 3:19c8eaf905e9 60 float ServoIn::readCalPulse(void){
jebradshaw 3:19c8eaf905e9 61 servoPulseOffset = ((float)servoPulseMax + (float)servoPulseMin) / 2.0;
jebradshaw 3:19c8eaf905e9 62 servoPulseScale = 1.0 / (((float)servoPulseMax - (float)servoPulseMin) / 2.0);
jebradshaw 3:19c8eaf905e9 63
jebradshaw 3:19c8eaf905e9 64 float pulseCal = ((float)servoPulse-servoPulseOffset)*servoPulseScale;
jebradshaw 3:19c8eaf905e9 65 if((pulseCal > 1.5) || (pulseCal < -1.5))
jebradshaw 3:19c8eaf905e9 66 return 0.0;
jebradshaw 3:19c8eaf905e9 67
jebradshaw 3:19c8eaf905e9 68 return ((float)servoPulse-servoPulseOffset)*servoPulseScale;
jebradshaw 3:19c8eaf905e9 69 }
jebradshaw 3:19c8eaf905e9 70
jebradshaw 1:b7cc6da72d09 71 void ServoIn::timeoutTest(void){
jebradshaw 1:b7cc6da72d09 72 if(!_t_state){
jebradshaw 1:b7cc6da72d09 73 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
jebradshaw 1:b7cc6da72d09 74 _t_state=1; //toggle t_sate (15ms has elapsed without servo edge
jebradshaw 1:b7cc6da72d09 75 }
jebradshaw 1:b7cc6da72d09 76 else{ //30 ms has elapsed without a valid servo pulse
jebradshaw 1:b7cc6da72d09 77 _pulseFlag = 0;
jebradshaw 1:b7cc6da72d09 78 _t_state=0;
jebradshaw 1:b7cc6da72d09 79 servoPulse = 0;
jebradshaw 1:b7cc6da72d09 80 _validPulseTimeout.attach(this, &ServoIn::timeoutTest, 0.015);
jebradshaw 1:b7cc6da72d09 81 }
jebradshaw 1:b7cc6da72d09 82 }
jebradshaw 1:b7cc6da72d09 83