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
- Committer:
- jebradshaw
- Date:
- 2015-05-21
- Revision:
- 3:19c8eaf905e9
- Parent:
- 1:b7cc6da72d09
- Child:
- 4:379f9ab5cb4b
File content as of revision 3:19c8eaf905e9:
// Uses Timer to read servo pulse on single input pin // J. Bradshaw 20140925 /* Copyright (c) 2015, jbradshaw (http://mbed.org) * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. * */ #include "mbed.h" #include "ServoIn.h" 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; servoPulseMax = 2100; servoPulseMin = 900; _t_state=0; } //function to read the servo pulse duration void ServoIn::PulseRead() { if(!_pulseFlag){ //if the flag is low, was waiting for high input interrupt this->pulseMeasure.reset(); //reset the timer _interrupt.fall(this, &ServoIn::PulseRead); _pulseFlag = 1; //set the pulse input flag } else{ 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; } float ServoIn::readCalPulse(void){ servoPulseOffset = ((float)servoPulseMax + (float)servoPulseMin) / 2.0; servoPulseScale = 1.0 / (((float)servoPulseMax - (float)servoPulseMin) / 2.0); float pulseCal = ((float)servoPulse-servoPulseOffset)*servoPulseScale; if((pulseCal > 1.5) || (pulseCal < -1.5)) return 0.0; return ((float)servoPulse-servoPulseOffset)*servoPulseScale; } 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); } }