Determine current pinmode

Projects Programming
1

Is there an easy way to determine the current pin mode of a digital pin? Something like pinMode(pin) ?

3

The pin mode is what you set it to. Not that difficult to remember, if it's important.

4

But if you want to you can:

uint8_t getPinMode(uint8_t pin){
	uint8_t bit = digitalPinToBitMask(pin);
	uint8_t port = digitalPinToPort(pin);
	volatile uint8_t *reg, *out;

	if (port == NOT_A_PIN) return 0xFF;

	reg = portModeRegister(port);
	out = portOutputRegister(port);
  
  //Check for tris (DDxn)
  if( (*reg) & bit ){ //is output
    return OUTPUT;
  }
  else{ //is input
    //Check state (PORTxn)
    if( (*out) & bit ){  //is set
      return INPUT_PULLUP;
    }
    else{ //is clear
      return INPUT;
    }
  }
}
5

septillion, that's what I was looking for. Looks like a modified version of the standard pinMode function.

I'm a little confused on what exactly, is being returned by digitalPinToBitMask. Is it an 8 bit mask, that always has a 1 in the position of the pin in the corresponding port?

6

It indeed is. And yes, a byte with a one in the position of the pin in question. You can use is to mask the rest of the port register.

7

Although you can determine the current pinMode of a pin why make things complicated ? As suggested earlier, just set a variable to the state that you set it to or a more general variable holding the current state of the program. After all, what else is going to change the mode apart from your program ?

8

Sometimes it can be usefull if a library does stuff as well. And why save something that's already saved? If you save it again you have to change that state as well..

1 Like
9

UKHeliBob, this Arduino is next to the electrical breaker panel in the garage. It's a Mega with an ethernet shield attached. All it does is report the state of inputs to a separate HTTP server, and do with outputs what the HTTP server requests.

It's a hassle to transfer *.ino files from my workstation in the office to the laptop, then take the laptop to the garage to upload to the Arduino. I would rather set it up so I can change the pinMode via HTTP, but before I do so I want to add a sanity check to the mode of the pin.

Why use a variable, for something that's already stored in a variable, then I would have to add a sanity check to make sure my variable corresponds to the existing variable.

10

I am intrigued. Can you share with us what the devices are that sometimes respond to outputs from the Arduino and sometimes provide inputs to the Arduino ?

11

Sounds like you might benefit from a standalone programmer - put your file on an SD card and walk out with the programmer, or just the SD card even and leave the programmer out there:
http://www.crossroadsfencing.com/BobuinoRev17/Programmer.html

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