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Topic: Servo library handling speed (Read 2039 times) previous topic - next topic



I have made a modification on the servo library to handle speed of the servo.

I dont know if i can propose it somewere.
If someone is interested, feel free to contact me




i would surely be interested in something like that.
Could you share the code here or somewhere else for a glimpse.


Here it is!

I haven't take too much time to made a clear and good code, but it is working.
I didnt change the name of the class, so I can change back to the older library just by changing the include.

I wrote an example.

The new function available are:

  void writeMicrosecondsWithSpeed(int value);
  void writeSpeed(int value);
  bool moving();

The others are working without modifications.




A quick look at your library made me wonder if values can become negative?  It seems that pulseWidths and speeds are always 0 or positive.
If not, there is quite some improvement to be made by using unsigned ints.

something like this:
Code: [Select]

class Servo
 uint8_t attach(uint8_t pin);           // attach the given pin to the next free channel, sets pinMode, returns channel number or 0 if failure
 uint8_t attach(uint8_t pin, uint16_t min, uint16_t max); // as above but also sets min and max values for writes.
 void detach();
 void write(uint16_t value);                   // if value is < 200 its treated as an angle, otherwise as pulse width in microseconds
 void writeMicroseconds(uint16_t value);   // Write pulse width in microseconds
 void writeWithSpeed(uint16_t value);
 void writeMicrosecondsWithSpeed(uint16_t value);
 void writeSpeed(uint16_t value);
 bool moving();
 uint8_t read();                        // returns current pulse width as an angle between 0 and 180 degrees
 uint16_t readMicroseconds();            // returns current pulse width in microseconds for this servo (was read_us() in first release)
 bool attached();                   // return true if this servo is attached, otherwise false
  uint8_t servoIndex;               // index into the channel data for this servo
  int8_t min;                       // minimum is this value times 4 added to MIN_PULSE_WIDTH    
  int8_t max;                       // maximum is this value times 4 added to MAX_PULSE_WIDTH  

write microSeconds() has a potential bug??: // if value == SERVO MIN subtracting - TRIM_DURATION makes it even smaller? is that correct?

furthermore you could use the constrain and skip the channel >=0 test.
Code: [Select]
void Servo::writeMicroseconds(int value)
 // calculate and store the values for the given channel
 byte channel = this->servoIndex;
 if( channel < MAX_SERVOS )                      // channel is byte so always >= 0
   value = constrain( value, SERVO_MIN(), SERVO_MAX() );  // shorter code
   value = value - TRIM_DURATION;     // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< ?

further a smaller bug in readMicroseconds() the signature should be unsigend int Servo::readMicroseconds()  or  uint16_t Servo::readMicroseconds()

Not reviewed all code but some of the remarks are applicable in multiple places of the lib

my 2 cents
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


many thanks rob for the code. works as said.
robtillaart, thanks for pointing that out. i will post the updated file soon.


when updated I will review it again
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

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