OUTPUT pins turns HIGH by default. Is this normal for the DUE?

Official Hardware Mega Due
1

Hi, thanks for checking out my first post.

I have just started with the Arduino DUE and have encountered a hopefully minor problem.

When declaring an OUTPUT pin using the pinMod function this pin is automatically set to HIGH, unlike when using the UNO in which case the OUTPUT pins are set to LOW by default. Is this normal behavior for the DUE or is there something fishy going on?

This particular problem is in itself no big deal since it is easy to set the pin LOW in the setup function but I’m concerned with sneaky issues as a result of changing from IDE 1.0.5 to 1.5.5-r2. Maybe the new IDE did not installed properly? That’s why I’m asking this maybe at first trivial question.

I’m using Windows 7 and Arduino IDE 1.5.5-r2

Thanks for helping a Newbie :slight_smile:

2

Hello ErgoGeek,
From a global definition, in DUE, all the pins defined as output have a default level of 1.
If you look at wiring_digital.c...

Arduino-1.5.X\hardware\arduino\sam\cores\arduino\wiring_digital.c

...the case OUTPUT for the switch in the pinMode function is..

case OUTPUT:
            PIO_Configure(
            	g_APinDescription[ulPin].pPort,
            	PIO_OUTPUT_1,
            	g_APinDescription[ulPin].ulPin,
            	g_APinDescription[ulPin].ulPinConfiguration ) ;

            /* if all pins are output, disable PIO Controller clocking, reduce power consumption */
            if ( g_APinDescription[ulPin].pPort->PIO_OSR == 0xffffffff )
            {
                pmc_disable_periph_clk( g_APinDescription[ulPin].ulPeripheralId ) ;
            }
        break ;

Notice PIO_OUTPUT_1 (line 57) which is defined as 1 in pio.h (line 55).

Pio.h is at

Arduino-1.5.X\hardware\arduino\sam\system\libsam\include

Regards,
Palliser

3

Thanks :slight_smile: