Are there instructions for the Arduino PID code? - c++

Question

I have the Makeblock Ultimate 2.0 kit which uses the Arduino MegaPi board. There is an Arduino PID example. But, there is no explanation of what the commands are and what the numbers are. Is there a manual or tutorial of something? Thanks in advance.
The example program follows:
/**
* \par Copyright (C), 2012-2016, MakeBlock
* #file Me_Megapi_encoder_pid_speed_MAM.ino
* #author MakeBlock
* #version V1.0.0
* #date 11/27/2016
* #brief Description: this file is sample code for Megapi encoder motor device.
*
* Function Call List:
* 1. uint8_t MeEncoderOnBoard::getPortB(void);
* 2. uint8_t MeEncoderOnBoard::getIntNum(void);
* 3. void MeEncoderOnBoard::pulsePosPlus(void);
* 4. void MeEncoderOnBoard::pulsePosMinus(void);
* 5. void MeEncoderOnBoard::setMotorPwm(int pwm);
* 6. double MeEncoderOnBoard::getCurrentSpeed(void);
* 7. void MeEncoderOnBoard::setSpeedPid(float p,float i,float d);
* 8. void MeEncoderOnBoard::setPosPid(float p,float i,float d);
* 7. void MeEncoderOnBoard::setPosPid(float p,float i,float d);
* 8. void MeEncoderOnBoard::setPulse(int16_t pulseValue);
* 9. void MeEncoderOnBoard::setRatio(int16_t RatioValue);
* 10. void MeEncoderOnBoard::runSpeed(float speed);
* 11. void MeEncoderOnBoard::loop(void);
*
* \par History:
* <pre>
* <Author> <Time> <Version> <Descr>
* Mark Yan 2016/07/14 1.0.0 build the new
* MAM 10/27/2016 1.0.0 Renamed Me_Megapi_encoder_pid_speed_MAM.ino
* </pre>
*/
#include <MeMegaPi.h>
MeEncoderOnBoard Encoder_1(SLOT1);
MeEncoderOnBoard Encoder_2(SLOT2);
void isr_process_encoder1(void)
{
if(digitalRead(Encoder_1.getPortB()) == 0)
{
Encoder_1.pulsePosMinus();
}
else
{
Encoder_1.pulsePosPlus();;
}
}
void isr_process_encoder2(void)
{
if(digitalRead(Encoder_2.getPortB()) == 0)
{
Encoder_2.pulsePosMinus();
}
else
{
Encoder_2.pulsePosPlus();
}
}
void setup()
{
attachInterrupt(Encoder_1.getIntNum(), isr_process_encoder1, RISING);
attachInterrupt(Encoder_2.getIntNum(), isr_process_encoder2, RISING);
Serial.begin(115200);
//Set PWM 8KHz
TCCR1A = _BV(WGM10);
TCCR1B = _BV(CS11) | _BV(WGM12);
TCCR2A = _BV(WGM21) | _BV(WGM20);
TCCR2B = _BV(CS21);
Encoder_1.setPulse(7);
Encoder_2.setPulse(7);
Encoder_1.setRatio(26.9);
Encoder_2.setRatio(26.9);
Encoder_1.setPosPid(1.8,0,1.2);
Encoder_2.setPosPid(1.8,0,1.2);
Encoder_1.setSpeedPid(0.18,0,0);
Encoder_2.setSpeedPid(0.18,0,0);
}
void loop()
{
if(Serial.available())
{
char a = Serial.read();
switch(a)
{
case '0':
Encoder_1.runSpeed(0);
Encoder_2.runSpeed(0);
break;
case '1':
Encoder_1.runSpeed(100);
Encoder_2.runSpeed(-100);
break;
case '2':
Encoder_1.runSpeed(200);
Encoder_2.runSpeed(-200);
break;
case '3':
Encoder_1.runSpeed(255);
Encoder_2.runSpeed(-255);
break;
case '4':
Encoder_1.runSpeed(-100);
Encoder_2.runSpeed(100);
break;
case '5':
Encoder_1.runSpeed(-200);
Encoder_2.runSpeed(200);
break;
case '6':
Encoder_1.runSpeed(-255);
Encoder_2.runSpeed(255);
break;
default:
break;
}
}
Encoder_1.loop();
Encoder_2.loop();
Serial.print( "Speed 1:\t");
Serial.print(Encoder_1.getCurrentSpeed());
Serial.print(" \t Speed 2:\t");
Serial.println(Encoder_2.getCurrentSpeed());
}

Answer 1

I tried to quickly search if there was anything online that maybe you had missed and I couldn't find much other than the source code for the MeMegaPi library (https://github.com/Makeblock-official/Makeblock-Libraries/tree/master/makeblock/src)
They also refer you back to the MegaBlocks website for more info which I guess you already did. So I'll explain a bit of what's going on here, though for the future, using the API will require you to read the source and that can be a bit daunting if you aren't familiar with C/C++. Anyway here goes:
MeEncoderOnBoard Encoder_1(SLOT1);
MeEncoderOnBoard Encoder_2(SLOT2);
void isr_process_encoder1(void)
First we have the instantiation of the Encoders to SLOT1 and SLOT2 for MeEncoderOnBoard Encoder_1 and MeEncoderOnBoard Encoder_2 respectively. SLOT1 and SLOT2 are aliases for connection 1 and connection 2 (/src/MePort.h) on your device (some kind of multi-pin cable I'd guess). These encoders also encode actions as we will see soon.
void isr_process_encoder1(void)
{
if(digitalRead(Encoder_1.getPortB()) == 0)
{
Encoder_1.pulsePosMinus();
}
else
{
Encoder_1.pulsePosPlus();;
}
}
void isr_process_encoder2(void)
{
if(digitalRead(Encoder_2.getPortB()) == 0)
{
Encoder_2.pulsePosMinus();
}
else
{
Encoder_2.pulsePosPlus();
}
}
Then we make the interrupt routines isr_process_encoder#s 1 and 2 for these encoders. For both we are reading port B (a pin on the connection slot) and performing an increment/decrement (depending on the value on portB) on what they call the pulse position.
void setup()
{
attachInterrupt(Encoder_1.getIntNum(), isr_process_encoder1, RISING);
attachInterrupt(Encoder_2.getIntNum(), isr_process_encoder2, RISING);
Serial.begin(115200);
In setup(), we attach the interrupt routines to the encoders and tell them to trigger on a rising-signal interrupt. After both encoders are set with interrupt handlers, we initiate serial communication on the arduino device with a baud-rate of 115200.
//Set PWM 8KHz
TCCR1A = _BV(WGM10);
TCCR1B = _BV(CS11) | _BV(WGM12);
TCCR2A = _BV(WGM21) | _BV(WGM20);
TCCR2B = _BV(CS21);
The next 4 lines of code is a bit of magic. The reasoning (as the comment suggests) is to set the PWM rate at 8KHz for what I'm assuming is the motors. The _BV is apparently how arduino sets bit values at low-level (making a big guess here)? Not too sure about this actually but I trust the people making this did their homework.
Encoder_1.setPulse(7);
Encoder_2.setPulse(7);
Encoder_1.setRatio(26.9);
Encoder_2.setRatio(26.9);
Encoder_1.setPosPid(1.8,0,1.2);
Encoder_2.setPosPid(1.8,0,1.2);
Encoder_1.setSpeedPid(0.18,0,0);
Encoder_2.setSpeedPid(0.18,0,0);
}
Now... admittedly, I have no idea what the numbers in setPulse, setRatio, setPosPid, or setSpeedPid represent... I hope that some kind of documentation for your PID motor is available because this is magic to me too. However these function calls are just setting these attributes on the Encoder objects (wish I had more to say :[)...
void loop()
{
if(Serial.available())
{
char a = Serial.read();
switch(a)
{
Next we have the main program loop. Starting off, we check if there is a Serial connection we can listen to. If yes, then we read a byte from the serial connection. if the byte we read corresponds to any case, we set the speeds on the Encoders as appropriate.
Encoder_1.loop();
Encoder_2.loop();
After this switch block, we perform the loop() call on our Encoders. According to the source, this is actually an update step where our settings are actually relayed to the device we are communicating with (I've been assuming it's a pair of motors).
Serial.print( "Speed 1:\t");
Serial.print(Encoder_1.getCurrentSpeed());
Serial.print(" \t Speed 2:\t");
Serial.println(Encoder_2.getCurrentSpeed());
}
Finally, we print out the speeds of the motors and then loop routine continues to do this [Read->Update->Print] cycle
Sorry I can't be more help with this, but this is all I can give you. good luck and I hope you can find documentation! I'm back off to work in my boring non-embedded programming job ;)