How to use a library within a library (Arduino) - c++

Question

My C++ skills are rather amateurish, but I’m trying to write a library for a differential drive robotic platform. The library in question needs to utilise a PID library and a rotary encoder library.
I’d like to utilise “levels of abstraction” to do this, rather than just having a massive “sketch” as it makes things a lot easier to read, and to be honest, is the point of object orientated programming. I.e i can write a class to control the a dc motor and just use multiple instances for each side. (I apologise if I’ve got the terminology wrong).
Essentially I’m having trouble utilising the third party libraries within my library.
If i was to write a simple sketch that used the two third party libraries, it would look like this (paraphrasing) -
#include <Arduino.h>
#include <RotaryEncoder.h>
#include <PID_v1.h>
#include <L298N.h>
char A_IN1 = 8;
char A_IN2 = 9;
char A_EN = 17;
char PIN_IN1 = 4;
char PIN_IN2 = 5;
double Setpoint, Output;
double Input = 0;
double Kp=1.3, Ki=15, Kd=0.01;
RotaryEncoder encoder(PIN_IN1, PIN_IN2, RotaryEncoder::LatchMode::TWO03);
PID myPID(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
void checkPosition(){
//some code that increments the encoder value
}
void setup(){
attachInterrupt(digitalPinToInterrupt(PIN_IN1), checkPosition, CHANGE);
pinMode(PIN_IN1, INPUT);
attachInterrupt(digitalPinToInterrupt(PIN_IN2), checkPosition, CHANGE);
pinMode(PIN_IN2, INPUT);
Setpoint = 0;
myPID.SetSampleTime(20);
myPID.SetMode(AUTOMATIC);
myPID.SetOutputLimits(0,255);
}
void loop(){
//loop code that uses PID to drive motors at appropriate speed etc etc
}
How does one go about implementing the two libraries into a custom library?
E.g two files L298N.cpp and L298N.h? Below is what I’ve tried, but no luck.
L298N.cpp
#include "Arduino.h"
#include "L298N.h"
#include <RotaryEncoder.h>
#include <PID_v1.h>
L298N::L298N(char IN1, char IN2, char EN, char A_INT1, char A_INT2){
pinMode(IN1, OUTPUT);
pinMode(IN2, OUTPUT);
pinMode(EN, OUTPUT);
attachInterrupt(digitalPinToInterrupt(A_INT1), checkPosition, CHANGE);
attachInterrupt(digitalPinToInterrupt(A_INT2), checkPosition, CHANGE);
pinMode(A_INT1, INPUT);
pinMode(A_INT2, INPUT);
RotaryEncoder encoder(A_INT1, A_INT2, RotaryEncoder::LatchMode::TWO03);
PID pid(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
pid.SetSampleTime(20);
pid.SetMode(AUTOMATIC);
pid.SetOutputLimits(0,255);
_IN1 = IN1;
_IN2 = IN2;
_EN = EN;
}
void L298N::checkPosition(){
encoder.tick(); // just call tick() to check the state.
}
double L298N::calculate_rpm(){
long new_position = encoder.getPosition();
long position_change;
double RPM;
if (new_position != old_position) {
tick_time = (millis() - last_time);
position_change = old_position - new_position;
RPM = 1 / ((double(tick_time / position_change) * 125)/1000/60); //10041 18538 = ticks per rev, 1 rev = 42.73cm
old_position = new_position;
last_time = millis();
}
else{
RPM = 0.0;
}
delay(20); // required for dagu as encoders are shit and only pulse 125 times per rev
return RPM;
}
void L298N::set_rpm(int rpm){
Setpoint = rpm;//covert_vel_rpm(vel);
Input = calculate_rpm();
pid.Compute();
if (Setpoint > 0.0){
forwards(char(Output));
}
else{
backwards(char(Output));
}
}
void L298N::forwards(char pwm){
digitalWrite(_IN1, HIGH);
digitalWrite(_IN2, LOW);
analogWrite(_EN, pwm);
return;
}
void L298N::backwards(char pwm){
digitalWrite(_IN1, LOW);
digitalWrite(_IN2, HIGH);
analogWrite(_EN, pwm);
return;
}
L298N.h
#ifndef L298N_h
#define L298N_h
#include "Arduino.h"
#include <RotaryEncoder.h>
#include <PID_v1.h>
class L298N
{
public:
L298N(char IN1, char IN2, char EN, char A_INT1, char A_INT2);
void set_rpm(int rpm);
private:
char _IN1, _IN2, _EN, _INT1, _INT2;
double last_time = millis();
double tick_time = 0;
long old_position = 0;
double Setpoint, Output;
double Input = 0;
double Kp=1.3, Ki=15, Kd=0.01;
RotaryEncoder encoder;//(char A_INT1, char A_INT2, RotaryEncoder::LatchMode::TWO03);
PID pid;//(double &Input, double &Output, double &Setpoint, double Kp, double Ki, double Kd, char DIRECT);
void checkPosition();
double calculate_rpm();
void forwards(char pwm);
void backwards(char pwm);
};
#endif
test.ino
#include <L298N.h>
#include <RotaryEncoder.h>
#include <PID_v1.h>
char A_IN1 = 8;
char A_IN2 = 9;
char A_EN = 17;
char A_INT1 = 3;
char A_INT2 = 4;
L298N left(A_IN1, A_IN2, A_EN, A_INT1, A_INT2);
void setup(){
}
void loop(){
left.set_rpm(20);
}
errors:
Arduino: 1.8.15 (Linux), Board: "Arduino Uno"
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp: In constructor
'L298N::L298N(char, char, char, char, char)':
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:7:67: error: no
matching function for call to 'RotaryEncoder::RotaryEncoder()'
L298N::L298N(char IN1, char IN2, char EN, char A_INT1, char A_INT2)
^ In file included from
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.h:10:0,
from /home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:3:
/home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:39:3:
note: candidate: RotaryEncoder::RotaryEncoder(int, int,
RotaryEncoder::LatchMode) RotaryEncoder(int pin1, int pin2,
LatchMode mode = LatchMode::FOUR0); ^~~~~~~~~~~~~
/home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:39:3:
note: candidate expects 3 arguments, 0 provided
/home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:23:7:
note: candidate: constexpr RotaryEncoder::RotaryEncoder(const
RotaryEncoder&) class RotaryEncoder
^~~~~~~~~~~~~ /home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:23:7:
note: candidate expects 1 argument, 0 provided
/home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:23:7:
note: candidate: constexpr
RotaryEncoder::RotaryEncoder(RotaryEncoder&&)
/home/ubuntu/Arduino/libraries/RotaryEncoder/src/RotaryEncoder.h:23:7:
note: candidate expects 1 argument, 0 provided
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:7:67: error: no
matching function for call to 'PID::PID()' L298N::L298N(char IN1,
char IN2, char EN, char A_INT1, char A_INT2)
^ In file included from
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.h:11:0,
from /home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:3:
/home/ubuntu/Arduino/libraries/PID/PID_v1.h:24:5: note: candidate:
PID::PID(double*, double*, double*, double, double, double, int)
PID(double*, double*, double*, // * constructor. links the PID to the Input, Output, and
^~~ /home/ubuntu/Arduino/libraries/PID/PID_v1.h:24:5: note: candidate expects 7 arguments, 0 provided
/home/ubuntu/Arduino/libraries/PID/PID_v1.h:20:5: note: candidate:
PID::PID(double*, double*, double*, double, double, double, int, int)
PID(double*, double*, double*, // * constructor. links the PID to the Input, Output, and
^~~ /home/ubuntu/Arduino/libraries/PID/PID_v1.h:20:5: note: candidate expects 8 arguments, 0 provided
/home/ubuntu/Arduino/libraries/PID/PID_v1.h:5:7: note: candidate:
constexpr PID::PID(const PID&) class PID
^~~ /home/ubuntu/Arduino/libraries/PID/PID_v1.h:5:7: note: candidate expects 1 argument, 0 provided
/home/ubuntu/Arduino/libraries/PID/PID_v1.h:5:7: note: candidate:
constexpr PID::PID(PID&&)
/home/ubuntu/Arduino/libraries/PID/PID_v1.h:5:7: note: candidate
expects 1 argument, 0 provided
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:13:70: error:
invalid use of non-static member function 'void
L298N::checkPosition()'
attachInterrupt(digitalPinToInterrupt(A_INT1), checkPosition, CHANGE);
^ In file included from
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:3:0:
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.h:33:7: note:
declared here void checkPosition();
^~~~~~~~~~~~~ /home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:14:70: error:
invalid use of non-static member function 'void
L298N::checkPosition()'
attachInterrupt(digitalPinToInterrupt(A_INT2), checkPosition, CHANGE);
^ In file included from
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.cpp:3:0:
/home/ubuntu/Arduino/libraries/L298N_driver/L298N.h:33:7: note:
declared here void checkPosition();
^~~~~~~~~~~~~ exit status 1 Error compiling for board Arduino Uno.
This report would have more information with "Show verbose output
during compilation" option enabled in File -> Preferences.
Any help of how to do this properly would be greatly appreciated. It’s just using a class within a class (terminology might be wrong) but this is quite trivial to do in Python.
Cheers!

Answer 1

You have several problems.
You said
PID and RotaryEncoder libraries are standard arduino libraries
That's wrong, those libraries are not standard, you have to install them using the Library Manager (otherwise it would have compiled).
Those are:
- RotaryEncoder, by Mathias Hertel
http://www.mathertel.de/Arduino/RotaryEncoderLibrary.aspx
- Arduino PID Library, by Brett Beauregard
https://github.com/br3ttb/Arduino-PID-Library
Local includes should use quotes, system/external includes must use brackets:
#include "L298N.h"
#include <RotaryEncoder.h>
RotaryEncoder does not have a default constructor, so you either initialize it using the initializer list or just remove the member variable.
PID doesn't have a default constructor either.
You cannot use a class member function as an interrupt handler. This:
attachInterrupt(digitalPinToInterrupt(A_INT1), checkPosition, CHANGE);
will never work. You may have to use a singleton or similar:
L298N left(A_IN1, A_IN2, A_EN, A_INT1, A_INT2);
// code
void int_checkPosition() {
left.checkPosition()
}
// more code
// this may go in setup()
attachInterrupt(digitalPinToInterrupt(A_INT2), checkPosition, CHANGE);
I changed the code in the constructor to make it look like this and compiles.
// encoder and pid initialized properly
L298N::L298N(byte IN1, byte IN2, byte mEN, byte A_INT1, byte A_INT2)
: encoder((int)A_INT1, (int)A_INT2, RotaryEncoder::LatchMode::TWO03)
, pid(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT)
{
piL298N::L298N(byte IN1, byte IN2, byte EN, byte A_INT1, byte A_INT2)
: encoder((int)A_INT1, (int)A_INT2, RotaryEncoder::LatchMode::TWO03)
, pid(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT)
{
pinMode(IN1, OUTPUT);
pinMode(IN2, OUTPUT);
pinMode(EN, OUTPUT);
// this doesn't work (use the recommendation above)
//attachInterrupt(digitalPinToInterrupt(A_INT1), checkPosition, CHANGE);
//attachInterrupt(digitalPinToInterrupt(A_INT2), checkPosition, CHANGE);
pinMode(A_INT1, INPUT);
pinMode(A_INT2, INPUT);
// you don't need this. in fact, it wasn't going to work
// because you needed it to be a class member.
//RotaryEncoder encoder((int)A_INT1, (int)A_INT2, RotaryEncoder::LatchMode::TWO03);
//PID pid(&Input, &Output, &Setpoint, Kp, Ki, Kd, DIRECT);
pid.SetSampleTime(20);
pid.SetMode(AUTOMATIC);
pid.SetOutputLimits(0,255);
_IN1 = IN1;
_IN2 = IN2;
_EN = EN;
}
It is up to you to fix the issue with the interrupt handler.

Answer 2

i think I understand what are you asking. Arduino (and many other IDE) has two different types o library
1) Local libraries
2) External Libraries
Local Libraries are those that you include by the syntaxis:
#include "Your_library.h"
External Libraries are those with the syntaxis:
#include <Your_library.h>
The difference between them is that the Local Libraries are supposed to be in the same folder of the proyect, it means that if you have a folder
Arduino/My_proyect/My_Proyect.ino
the library should be in
Arduino/My_proyect/Your_library.h
Instead, external Libraries are in the Arduino "libraries" folder
Arduino/libraries/Your_library/Your_library.h
Maybe the problem with your code is that you are using the bad type of syntaxis for the library, try to put all the libraries you want to use (.h and .cpp) in the same file and create a folder in the arduino "libraries" folder, then, include your librarys using the external syntaxis
#include <Folder_name.h>
This should work!