ADC — `pymcu.hal.adc`#

from pymcu.hal.adc import AnalogPin

Analog-to-digital conversion. Wraps the AVR ADC peripheral.

class `AnalogPin`#

`AnalogPin(channel: str)`#

Initializes the ADC for the given channel. On ATmega328P, channel is an Arduino analog pin name ("A0" through "A5") which maps to ADC channels 0–5 on PORTC.

Methods#

Method	Return type	Description
`start()`	—	Begin a conversion (sets ADSC in ADCSRA)
`read() -> uint16`	`uint16`	10-bit result (0–1023)
`read_u16() -> uint16`	`uint16`	16-bit scaled result (0–65535)
`start_conversion()`	—	Start ADC with interrupt enabled
`read_result() -> uint16`	`uint16`	Read ADCL/ADCH result registers directly
`value() -> uint16`	`uint16`	Same as `read_result()`

Examples#

Polling conversion#

from pymcu.hal.adc import AnalogPin
from pymcu.types import ptr, uint8, uint16

ADCSRA: ptr[uint8] = ptr(0x7A)

def main():
    adc = AnalogPin("A0")
    while True:
        adc.start()
        while ADCSRA[6]:    # wait for ADSC to clear
            pass
        result: uint16 = adc.read()
        # result is 0-1023

Scaled reading (16-bit)#

from pymcu.hal.adc import AnalogPin
from pymcu.types import uint16

adc = AnalogPin("A0")
adc.start()
# ... wait for conversion ...
val: uint16 = adc.read_u16()    # 0-65535 (10-bit × 64)

Interrupt-driven#

from pymcu.hal.adc import AnalogPin
from pymcu.types import uint16

sensor = AnalogPin("A0")
result: uint16 = 0

@interrupt(0x002A)    # ADC Complete vector (ATmega328P)
def on_adc():
    global result
    result = sensor.read_result()

def main():
    sensor.start_conversion()
    while True:
        pass

Internal temperature sensor#

The ATmega328P has a built-in temperature sensor connected to ADC channel 8. No external components are required.

from pymcu.hal.adc import adc_read_temp_raw
from pymcu.types import uint16

def main():
    raw: uint16 = adc_read_temp_raw()
    # Factory calibration: ~314 counts at 25 °C, ~1 count per degree
    # No EEPROM calibration data — accuracy is ±10 °C typical

Item	Detail
Import	`from pymcu.hal.adc import adc_read_temp_raw`
Return type	`uint16` — raw ADC count (channel 8, internal 1.1 V reference)
Typical value	~314 at 25 °C
Scale	~1 count / °C (uncalibrated)
Accuracy	±10 °C typical (factory), ±2 °C with calibration

For a rough Celsius estimate (calibration-free):

temp_c: int = raw - 289    # offset for 25 °C baseline — adjust per chip

Note

For accurate temperature readings use a calibrated external sensor such as DS18B20 or DHT11.

ATmega328P ADC register map#

Register	Address	Description
`ADMUX`	`0x7C`	MUX select + reference voltage
`ADCSRA`	`0x7A`	Control: ADEN, ADSC, ADIE, prescaler
`ADCSRB`	`0x7B`	Free-running mode
`ADCL`	`0x78`	Result low byte
`ADCH`	`0x79`	Result high byte

ADC — pymcu.hal.adc#

class AnalogPin#

AnalogPin(channel: str)#