Reading a pin as an input on AVR XMEGAs

Question

I have been messing with AVR's XMEGA line. They are pretty amazing microcontrollers. However, Atmel changed much with this new line. I am trying to detect a pin going low.

I have tried to set the PINnCTRL register to every combination with no luck. I can detect the pin going HIGH but not the other way around. Below is the working code for turning on the LED on pin 5 when pin 6 goes high. However, I wanted to do the same thing, just instead of when pin 6 goes high, I would like to have pin 6 go low and turn on the LED on pin 5.

Anyhow, I have not seen a lot of XMEGA stuff on here, so I thought I would try.

I am using AVR Studio and the ATXmega256A3 microcontroller.

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AVR PINnCTRL Configuration Register Table (at least for the pull sections 0b00xxx000) FULL DATASHEET HERE: http://www.atmel.com/dyn/resources/prod_documents/doc8077.pdf.

On page 131 (section 13.4) this lists the definition of all of table below. NOTE: the PINxCTRL register contains more than just the pullups for settings. The bits I am working with are these: 00xxx000 The x's correspond with the listing below.

Table 13-4. Output/Pull Configuration
                                                          Description
  OPC[2:0]  Group Configuration       Output configuration        Pull configuration
     000    TOTEM                     Totempole                   (N/A)
     001    BUSKEEPER                 Totempole                   Bus keeper
     010    PULLDOWN                  Totempole                   Pull-down (on input)
     011    PULLUP                    Totempole                   Pull-up (on input)
     100    WIREDOR                   Wired OR                    (N/A)
     101    WIREDAND                  Wired AND                   (N/A)
     110    WIREDORPULL               Wired OR                    Pull-down
     111    WIREDANDPULL              Wired AND                   Pull-up

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#include <stdio.h>
#include <avr\io.h>
#define F_CPU 32000000UL
#include <util\delay.h>

void Config32MHzClock(void);

int main(void)
{
    //Init stuff..
    Config32MHzClock();
    CLK.PSCTRL = 0x00; // No division on peripheral clock.
    PORTCFG.CLKEVOUT = PORTCFG_CLKOUT_PE7_gc;

    PORTA.DIR = (1 << 5);  //Sets pin5 as an output (led)

    //011 PULLUP Totempole Pull-up (on input) is what is set
    PORTA.PIN6CTRL = (0x30);  //Sets pullup on input on pin 6.
    PORTA.OUT = (1<<5);       //Turn on the LED

    while(1){                   //Never ending main loop.
        if (PORTA.IN & (1<<6))  //If pin 6 goes HIGH.
            PORTA.OUT = (0x00); //Turn off LED.

        PORTA.OUT = (1 << 5); //Turn LED back on.
    }
}

//Function to setup clock..
void Config32MHzClock(void)
{
    CCP = CCP_IOREG_gc; //Security signature to modify clock
    // Initialize clock source to be 32 MHz internal oscillator (no PLL).
    OSC.CTRL = OSC_RC32MEN_bm; // Enable internal 32 MHz oscillator.
    while(!(OSC.STATUS & OSC_RC32MRDY_bm)); // Wait for oscillator ready
    CCP = CCP_IOREG_gc; //Security signature to modify clock
    CLK.CTRL = 0x01; //Select sysclock 32 MHz oscillator
};

Answer 1

There are a few concerns I have.

1) Unless you start counting pins from 0, (1 << 5) is actually pin 6.

2) According to the code, pin 6 going high causes the LED to turn off.

3) Immediately after turning the LED off, you turn it back on. Turning it back on should probably be in an else block.

4) This part of your question is confusing.

I wanted to do the same thing just instead of when pin6 goes high I would like to have pin 6 go low and turn on the led on pin5.

The reason it is confusing is because you say that pin 6 is an input, and then you say you want to drive pin 6 low (which implies an output).