Hardware Namespace Reference

This module is the interface to the Hardware via GPIO, ADC and Counter. More...

Enumerations
enum	LedState : uint8_t { LED_Off = 0x00u, LED_Green = 0x01u, LED_Red = 0x02u }
	The state of the current display (LED). More...

Functions
void	setup ()
	Setup the MCU hardware to the initial values. More...
void	setLedState (LedState ledState)
	Enable or disable the status LEDs. More...
void	sendDoneSignal ()
	Send the done signal. More...
bool	isButtonPressed ()
	Get the status of the button. More...
uint16_t	getVoltageValue ()
	Read the current voltage value. More...
void	shutdownVoltageMeasurement ()
	Shutdown voltage measurement to save power. More...
uint8_t	getOscillatorFrequency ()
	Try to determine the frequency. More...
void	shutdownOscillatorCounter ()
	Shutdown the counter to save power. More...

Detailed Description

This module is the interface to the Hardware via GPIO, ADC and Counter.

Enumeration Type Documentation

LedState

enum Hardware::LedState : uint8_t

The state of the current display (LED).

Enumerator
LED_Off	The LED is off.
LED_Green	The green LED is on.
LED_Red	The red LED is on.

Definition at line 34 of file Hardware.h.

              : uint8_t {
    LED_Off   = 0x00u, 
    LED_Green = 0x01u, 
    LED_Red   = 0x02u, 
};

Function Documentation

getOscillatorFrequency()

uint8_t Hardware::getOscillatorFrequency

(

)

Try to determine the frequency.

I assume the frequency from the oscillator will be somewhere in a kHz range. The maximum frequency of the oscillator is somewhere around 140kHz the lowest (100% water) around 40kHz. Measuring the number of rising edges for ~1ms should generate a usable value.

If no signal is received, 0x00 is returned. If the counter overflows, 0xff is returned. (This should not happen).

Returns

The approximate oscillator frequency in kHz.

Definition at line 136 of file Hardware.cpp.

{
    // Select external clock source, T0/Pin 7 to enable the counter.
    TCCR0B = (_BV(CS00)|_BV(CS01)|_BV(CS02));
    // Reset the counter.
    TCNT0 = 0;
    // Clear the overflow flag.
    TIFR0 = _BV(TOV0);
    // Wait ~1ms for the result.
    Tool::delayMs(1);
    // Read the result.
    uint8_t result = TCNT0;
    // Check the overflow flag.
    if ((TIFR0 & _BV(TOV0)) != 0) {
        result = 0xff;
    }
    return result;
}

getVoltageValue()

uint16_t Hardware::getVoltageValue

(

)

Read the current voltage value.

Returns

The current voltage value. ~23 per 0.1V.

Definition at line 105 of file Hardware.cpp.

{
    // Collect a number of samples and get the average out of them.
    uint16_t values = 0u;
    const uint8_t sampleCount = 32u;
    for (uint8_t i = 0; i < sampleCount; ++i) {
        // Start the conversion.
        ADCSRA |= _BV(ADSC);
        // Wait for the conversion to finish.
        while ((ADCSRA & _BV(ADSC)) != 0) {
            _NOP();
        }
        // Read the value.
        uint16_t value = ADCL;
        value |= ((uint16_t)(ADCH) << 8);
        // Add it up to get the average.
        values += value;
    }
    // Return the average of all samples.
    return (values / sampleCount);
}

isButtonPressed()

bool Hardware::isButtonPressed

(

)

Get the status of the button.

Returns

true if the push button is pressed.

Definition at line 99 of file Hardware.cpp.

{
    return ((PINB & _BV(PINB3)) != 0);
}

sendDoneSignal()

void Hardware::sendDoneSignal

(

)

Send the done signal.

Definition at line 89 of file Hardware.cpp.

{
    // Just set the done line to high for 10ms.
    PORTB |= _BV(DDB0);
    Tool::delayMs(10);
    PORTB &= ~_BV(DDB0);
    Tool::delayMs(100);
}

setLedState()

void Hardware::setLedState

(

LedState

ledState

)

Enable or disable the status LEDs.

Parameters

ledState

The LED state.

Definition at line 69 of file Hardware.cpp.

{
    switch (ledState) {
    case LED_Off:
    default: // Set PB0 to Hi-Z;
        DDRB &= (~_BV(DDB1));
        PORTB &= (~_BV(PORTB1));
        break;
    case LED_Green: // Set PB0 to HIGH.
        DDRB |= _BV(DDB1);
        PORTB |= _BV(PORTB1);
        break;
    case LED_Red: // Set PB0 to LOW.
        DDRB |= _BV(DDB1);
        PORTB &= (~_BV(PORTB1));
        break;
    }
}

setup()

void Hardware::setup

(

)

Setup the MCU hardware to the initial values.

Definition at line 35 of file Hardware.cpp.

{
    // Set the pre-scaler frequency to 2.4MHz.
    CLKPR = _BV(CLKPCE); // First set the CE bit.
    CLKPR = _BV(CLKPS1); // ...then set the clock frequency.
    
    // Setup PORTB:
    // - PB0/Pin 5 as output (done signal).
    // - PB1/Pin 6 keep tristate Hi-Z for the display (LED).
    // - PB2/Pin 7 as input (oscillator) used for counter.
    // - PB3/Pin 2 as input (button).
    DDRB = _BV(DDB0);
    // Make sure all outputs are low.
    PORTB = 0;
    
    // Setup the ADC for PB4/Pin 3
    // - Use the internal 1.1V source.
    // - Left align the result.
    // - Use PB4/Pin 3 as input.
    ADMUX = (_BV(REFS0)|_BV(MUX1));
    // - Enable the ADC (to allow enough time to stabilize)
    // - Prescaler to 128, to get 75kHz which should be get an accurate result.
    ADCSRA = (_BV(ADEN)|_BV(ADPS2)|_BV(ADPS1)|_BV(ADPS0));
    // - Disable the digital in on for PB0, PB1, PB4 to reduce power usage.
    DIDR0 = (_BV(AIN0D)|_BV(AIN1D)|_BV(ADC2D));
    
    // Setup the counter.
    // - no compare match, no PWM, no compare output.
    TCCR0A = 0;
    // - No Interrupt
    TIMSK0 = 0;
}

shutdownOscillatorCounter()

void Hardware::shutdownOscillatorCounter

(

)

Shutdown the counter to save power.

After calling this method, the getOscillatorFrequency() call will not work anymore.

Definition at line 156 of file Hardware.cpp.

{
    // Stop the counter and shutdown the module to save power.
    TCCR0B = 0;
    PRR |= _BV(PRTIM0);
}

shutdownVoltageMeasurement()

void Hardware::shutdownVoltageMeasurement

(

)

Shutdown voltage measurement to save power.

Definition at line 128 of file Hardware.cpp.

{
    // Disable the ADC to save power.
    ADCSRA &= ~_BV(ADEN); // Disable the ADC
    PRR |= _BV(PRADC); // Shutdown the ADC to save power.
}