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Servo value read and write fixes

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Values that were written and then read would be different due to using
map.
If user defined a different min/max pulse width would cause the
read/write to incorrectly calculate the pulse width.
This commit is contained in:
Makuna 2016-01-25 16:01:43 -08:00
parent e75c3d8444
commit acb7dc0681
1 changed files with 23 additions and 4 deletions
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27
libraries/Servo/src/esp8266/Servo.cpp
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@ -53,6 +53,21 @@ static uint8_t s_servoCount = 0; // the total number of attached s_se
#define SERVO_INDEX_TO_TIMER(servoIndex) ((ServoTimerSequence)(servoIndex / SERVOS_PER_TIMER)) // returns the timer controlling this servo
#define SERVO_INDEX(timerId, channel) ((timerId * SERVOS_PER_TIMER) + channel) // macro to access servo index by timer and channel
// similiar to map but will have increased accuracy that provides a more
// symetric api (call it and use result to reverse will provide the original value)
//
int improved_map(int value, int minIn, int maxIn, int minOut, int maxOut)
{
const int rangeIn = maxIn - minIn;
const int rangeOut = maxOut - minOut;
const int deltaIn = value - minIn;
// fixed point math constants to improve accurancy of divide and rounding
const int fixedHalfDecimal = 1;
const int fixedDecimal = fixedHalfDecimal * 2;
return ((deltaIn * rangeOut * fixedDecimal) / (rangeIn) + fixedHalfDecimal) / fixedDecimal + minOut;
}
//------------------------------------------------------------------------------
// Interrupt handler template method that takes a class that implements
// a standard set of methods for the timer abstraction
@ -218,8 +233,10 @@ void Servo::write(int value)
// treat values less than 544 as angles in degrees (valid values in microseconds are handled as microseconds)
if (value < MIN_PULSE_WIDTH) {
// assumed to be 0-180 degrees servo
value = max(0, min(180, value));
value = map(value, 0, 180, _minUs, _maxUs);
value = constrain(value, 0, 180);
// writeMicroseconds will contrain the calculated value for us
// for any user defined min and max, but we must use default min max
value = improved_map(value, 0, 180, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);
}
writeMicroseconds(value);
}
@ -229,7 +246,7 @@ void Servo::writeMicroseconds(int value)
// ensure channel is valid
if ((_servoIndex < MAX_SERVOS)) {
// ensure pulse width is valid
value = max(_minUs, min(_maxUs, value));
value = constrain(value, _minUs, _maxUs);
s_servos[_servoIndex].usPulse = value;
}
@ -237,7 +254,9 @@ void Servo::writeMicroseconds(int value)
int Servo::read() // return the value as degrees
{
return map(readMicroseconds(), _minUs, _maxUs, 0, 180);
// read returns the angle for an assumed 0-180, so we calculate using
// the normal min/max constants and not user defined ones
return improved_map(readMicroseconds(), MIN_PULSE_WIDTH, MAX_PULSE_WIDTH, 0, 180);
}
int Servo::readMicroseconds()