Admin at 02:54, 1 February 2016

2016-02-01T02:54:35Z

New page

Here's a snippet of code to use the ADC from an ATtiny84 microcontroller. In this example, the code was written for a t84 (Atmel AVR ATtiny84), but with minimal adjustments this code should work on microcontrollers from the same family (such as the ATtiny25, ATtiny45, ATtiny24, ATtiny44 and ATiny85) as well.

<pre>

void initADC()
{
/* this function initialises the ADC

ADC Notes

Prescaler

ADC Prescaler needs to be set so that the ADC input frequency is between 50 - 200kHz.

Example prescaler values for various frequencies

Clock Available prescaler values
---------------------------------------
1 MHz 8 (125kHz), 16 (62.5kHz)
4 MHz 32 (125kHz), 64 (62.5kHz)
8 MHz 64 (125kHz), 128 (62.5kHz)
16 MHz 128 (125kHz)

below example set prescaler to 16 for mcu running at 1MHz

*/

ADMUX =
(0 << REFS1) | // Sets ref. voltage to Vcc, bit 1
(0 << REFS0) | // Sets ref. voltage to Vcc, bit 0
(0 << MUX5) | // use ADC1 for input (PA1), MUX bit 5
(0 << MUX4) | // use ADC1 for input (PA1), MUX bit 4
(0 << MUX3) | // use ADC1 for input (PA1), MUX bit 3
(0 << MUX2) | // use ADC1 for input (PA1), MUX bit 2
(0 << MUX1) | // use ADC1 for input (PA1), MUX bit 1
(1 << MUX0); // use ADC1 for input (PA1), MUX bit 0

ADCSRA =
(1 << ADEN) | // Enable ADC
(1 << ADPS2) | // set prescaler to 16, bit 2
(0 << ADPS1) | // set prescaler to 16, bit 1
(0 << ADPS0); // set prescaler to 16, bit 0

ADCSRB =
(1 << ADLAR); // left shift result (for 8-bit values)
// (0 << ADLAR); // right shift result (for 10-bit values)
}

int main( void )
{

initADC();

while(1)
{

ADCSRA |= (1 << ADSC); // start ADC measurement
while (ADCSRA & (1 << ADSC) ); // wait till conversion complete

if (ADCH > 128)
{
// ADC input voltage is more than half of VCC

} else {

// ADC input voltage is less than half of VCC

}

}

return 0;
}
</pre>

See also:

* [[ATtiny84_PWM]]
* [[ATtiny85_ADC]]
* [[C and C++]]

ATtiny84 ADC - Revision history

Admin at 02:54, 1 February 2016