This is a library for AVR-Microcontrollers. It is used to teach the basics of microcontrollers (GPIO-pins, Interrupts, Timer/Counter and RS232-Interface) to students on a technical high-school.

The LitecAVRTools-library is highly inspired by the AVRTools-library from Igor Mikolic-Torreira.

For now the ATmega2560 and the Atmega328p are supported.

The LitecAVRTools share some design goals with the original AVRTools-Library:

• avrgcc is used as compiler, replacing the Arduino-IDE and its core-library. Another IDE can be used, such as Atmel-Studio. Alltough the Arduino-IDE could still be used, if one doesn't provide a setup() and a loop() function, but simply a main() function. Therfore every IDE is suitable, that allows programming Arduino-scetches, for example Microsoft-Visual-Studio with the Visual-Micro-plugin.
• Programming should be nearly as comfortable as using the Arduino-IDE and its core library.
• Bits in special-function-registers of the Microcontroller don't need to be manipulated directly. Instead functions (macros) with meaningful names are used. For example, to make pin PB3 (pin number 3 of Port B) an output, it is not necessary to write DDRB |= (0x01<<3);, but one can write setGpioPinModeOutput( GpioPin( B, 3) );

However, the LitecAVRTools-library has some different design-goals compared to the AVRTools-Library:

• Pins are not named according to the names used on Arduino-Mega- and Arduino-Uno-Boards. The pin-names used by LitecAVRTools follow the datasheet of the ATmega-Microcontrollers. For example pin number 0 of port A in the datasheet is referred to as PA0.
• It is possible to program a whole port (8 pins at once). For example this is useful for driving a seven-segment-display.
• PWM-outputs and analog-inputs are (will be) supported by the library. But this is not done by programming pins. Instead one has to program a Timer/Counter to use PWM-outputs, or the Analog-to-Digital-Converter to use analog inputs.
• It is necessary to know/find information contained in the datasheet of the microcontroller. For example if a PWM-output is used, it is necessary to know, that the output-compare-pin A of Timer/Counter1 (OC1A) on the Atmega2560 is an alternative function of Pin PB5, and that this pin must first be programmed as ordinary output.

Add the file GpioPinMacros.h to your project. This is the only file needed for the GPIO-module of LitecAVRTools.

To use the following example, connect a push-button between GPIO-pin PD2 (the pin number 2 of Port D) and GND. Connect (up to) four LEDs between the pins PA0...PA3 and VCC. Don't forget the series resistors!

Each time the push-button is pressed, the next LED lights up.

#include <util/delay.h>

#include "GpioPinMacros.h"

#define buttonPin     GpioPin( D, 2 )

int main()
{
    int ledNo;
    int actualLed = 0;

    //
    //initialize button and LEDs
    //
    setGpioPinModeInputPullup( buttonPin );

    for (ledNo = 0; ledNo<4; ledNo++)
    {
        setGpioPinModeOutput( GpioPin ( A, ledNo ) );
        //High-level turns LED off:
        writeGpioPinDigital( GpioPin ( A, ledNo), c_High );
    }

    //turn on LED number <actualLed>
    writeGpioPinDigital( GpioPin( A, actualLed ), c_Low );

    while(1)
    {
        //is button pushed (produces a Low-voltage-level)?
        //if yes: switch to next LED
        if (readGpioPinDigital( buttonPin ) == c_Low )
        {
            //instead of
            //writeGpioPinDigital( GpioPin( A, actualLed ), c_High) :
            setGpioPinHigh( GpioPin ( A, actualLed) ); //turn off Led
            actualLed++; //switch to next LED
            if ( actualLed > 3 )
                actualLed = 0;
            setGpioPinLow( GpioPin ( A, actualLed ) ); //turn on Led
        }

        _delay_ms(150);
    }

    return 0;
}

Beginners watch out: The functions used in this program are not functions but macros.If you have Syntax-Errors, normally avrgcc does not report them in your program, but in GpioPinMacros.h

Further documentation can be found in the folder named doc. There is a .md-File for each module.

To use the more sophisticated features of the AVR-microcontrollers (for example PWM with Timer/Counter), see the relevant section of the datasheet of the ATmega328p / Atmega2560.