analogRead8bit

// This code is modified from the original analogRead function provided in Arduino's source code (wiring_analog.c)
// This function can be appended directly to the stock file wiring_analog.c

uint8_t analogRead8bit(uint8_t pin)
{
    uint8_t result;
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
    if (pin >= 54) pin -= 54; // allow for channel or pin numbers
#elif defined(__AVR_ATmega32U4__)
    if (pin >= 18) pin -= 18; // allow for channel or pin numbers
#elif defined(__AVR_ATmega1284__) || defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega644__) || defined(__AVR_ATmega644A__) || defined(__AVR_ATmega644P__) || defined(__AVR_ATmega644PA__)
    if (pin >= 24) pin -= 24; // allow for channel or pin numbers
#elif defined(analogPinToChannel) && (defined(__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__))
    pin = analogPinToChannel(pin);
#else
    if (pin >= 14) pin -= 14; // allow for channel or pin numbers
#endif

#if defined(__AVR_ATmega32U4__)
    pin = analogPinToChannel(pin);
    ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#elif defined(ADCSRB) && defined(MUX5)
    // the MUX5 bit of ADCSRB selects whether we're reading from channels
    // 0 to 7 (MUX5 low) or 8 to 15 (MUX5 high).
    ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#endif

#if defined(ADMUX)
    ADMUX = (analog_reference << 6) | (pin & 0x07);
#endif

    // without a delay, we seem to read from the wrong channel
    // delay(1);

#if defined(ADCSRA)
    // start the conversion
    sbi(ADCSRA, ADSC);

    // ADSC is cleared when the conversion finishes
    while (bit_is_set(ADCSRA, ADSC));

    //read only ADCH, 8 bits
    result = ADCH;
#else
    // we don't have an ADC, return 0
    result = 0;
#endif

    // combine the two bytes
    return result;
}