Using #if - #endif

Projects Programming
1 
#if defined PCB_Version_2_0
const int LEDpin = A1;        //power indicator
const int analogPin = A2;     //joystick connected to A2
const int buttonPin = A5;     //program button on digital pin 2
const String splash = "Microphone Controller Version 2.0";
#elif defined PCB_Version_3_0
const int LEDpin = A1;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = A5;     //program button
const int potPin = A6;        //potentiometer
const String splash = "Microphone Controller Version 3.0";
#endif

I have this code before my Setup() block. Is it okay to use this again later within my loop, something like this:

#if defined PCB_Version_3_0
   ...check on the potentiometer
#endif

because I need to do this, only if I'm using the Version 3 (Ver 2 doesn't have a POT). I've tried adding this into my code and it compiles, but I just want to make sure I'm not doing something wrong. I'm not real familiar with #if.
Thanks.

1 Like
2

AFAIK you can use that as many times as you like.

Rob

3

While it is perfectly acceptable to do it that way, a more common approach is to set the state of a variable and then use that. For example:

#define VERSION2 2
#define VERSION3 3

int whichPCB;

#if defined PCB_Version_2_0
whichPCB = VERSION2 ;
const int LEDpin = A1;        //power indicator
const int analogPin = A2;     //joystick connected to A2
const int buttonPin = A5;     //program button on digital pin 2
const String splash = "Microphone Controller Version 2.0";
#elif defined PCB_Version_3_0
whichPCB = VERSION3 ;
const int LEDpin = A1;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = A5;     //program button
const int potPin = A6;        //potentiometer
const String splash = "Microphone Controller Version 3.0";
#endif

// ...a bunch of code...
if (whichPCB == VERSION3 ) {
   // do whatever...
}
4

While it is perfectly acceptable to do it that way, a more common approach is to set the state of a variable and then use that. For example:

The problem with that approach is that:

if (whichPCB == VERSION3 ) {
   // do whatever...
}

will be compiled and included in the hex file regardless of which version of the board is being used. Using #if/#endif, the code in between will only be compiled and included in the hex file if the relevant board is being used.

5

Yep...you're right.

6

This code is all located before my setup(). Is it OK to put a second #define inside the #ifdef section. See the second line of this code:

...
#elif defined PCB_Version_3_0
#define DownPotentiometer A6  //POT to regulate the max down speed (Ver 3 only)
const int LEDpin = A1;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = A5;     //program button
const int potPin = A6;        //potentiometer
const String splash = "Microphone Controller Version 3.0";
#elif defined PCB_Version_4_0
const int LEDpin = A5;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = 2;      //program button
const String splash = "Microphone Controller Version 4.0";
#endif
7

Is it OK to put a second #define inside the #ifdef section.

Yes. Be careful how you try to use that name later. It needs to be in an #if/#endif block using the same name as the block it is defined in.

8

Here's what I had in mind:

This part before my setup(), defines the PCB, and also some versions will have a POT on an analogPin, so you see DownPotentiometer is defined in version 3.

#if defined PCB_Version_2_0
const int LEDpin = A1;        //power indicator
const int analogPin = A2;     //joystick connected to A2
const int buttonPin = A5;     //program button on digital pin 2
const String splash = "Microphone Controller Version 2.0";
#elif defined PCB_Version_3_0
#define DownPotentiometer A6  //POT to regulate the max down speed (Ver 3 only)
const int LEDpin = A1;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = A5;     //program button
const int potPin = A6;        //potentiometer
const String splash = "Microphone Controller Version 3.0";
#elif defined PCB_Version_4_0
const int LEDpin = A5;        //Power indicator
const int analogPin = A3;     //joystick connection pin
const int buttonPin = 2;      //program button
const String splash = "Microphone Controller Version 4.0";
#elif defined  PCB_Version_4_2
const int LEDpin = A5;        //Power indicator
const int analogPin = A2;     //joystick connection pin
const int buttonPin = 2;      //program button
const String splash = "Microphone Controller Version 4.2";
#endif

And then in my motor function if DownPotentiometer is defined, if reads the value from that POT, otherwise, it assumes there is no POT.

void motorDown(unsigned long reading) {  //run the motor down (1 to 799 is 0% to 100%)
int maxSpeed = 799; //set max down speed to 100%
#ifdef DownPotentiometer //is there a POT for adjusting the max down speed?
  int analogVal = analogRead(DownPotentiometer); //read the val, will be  0 to 1023
  //map function:  map(value, fromLow, fromHigh, toLow, toHigh)
  maxSpeed = map (analogVal, 0,1023, 400, 799); //remap the val; 799 is 100% motor speed 
#endif

  //int mappedVal = fscale( joystick.down, joystick.center, 799, 1, reading, 4.5); //the curve is pos, not neg, b/c the map is inverted
  int mappedVal = fscale( joystick.down, joystick.center - CenterDebounce, maxSpeed, 50, reading, 4.5); //the curve is pos, not neg, b/c the map is inverted
  digitalWrite(motorUpPin, LOW);  //going up
  digitalWrite(motorDownPin, HIGH);  //pulled low for motor ground
  analogWriteSAH(mappedVal);  //Set the PWM for the motor speed
  Serial.print("Motor Down Speed: ");
  Serial.println(mappedVal);
}