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Getting Started with the ADC Class

This guide explains how to use the ADC class to read analog signals from a Raspberry Pi Pico or Pico W and convert them to voltage or real-world values.

Initialization

1. Create an ADC instance

from core.io import ADC

# Example: pin 26, no extra vref, scaling or offset
adc = ADC(pin=26)

Parameters

  • pin: GPIO pin number connected to the analog signal.
  • vref: Reference voltage for conversion (default 3.3V).
  • scale: Multiplier for real-world conversion (default 1.0).
  • offset: Offset added after scaling (default 0.0).

Calibration

The scale and offset values can be used to calibrate the ADC to match your specific application. Better to use the calibration function adc.calibrate(real voltge) instead.This requires a known real-world value to be provided.

Reading Values

2. Raw ADC Reading

raw_value = adc.raw()
print(f"Raw ADC: {raw_value}")
  • Returns a value between 0 and 65535.

3. Voltage Measurement

v = adc.voltage()
print(f"Voltage: {v:.2f} V")
  • Converts the raw reading into volts.
Equation: Calculating Voltage

The equation for voltage conversion is: $$ Voltage = \frac{\text{raw}}{65535} \cdot V_{\text{ref}} $$

the raw value is the raw reading from the ADC as an integer between 0 and 65535 (read_u16), and Vref is the reference voltage in volts.

4. Real-World Value

real_value = adc.real()
print(f"Scaled value: {real_value}")
  • Applies scaling and offset to get real-world units (like temperature or light intensity).

Sampling

5. Collect Multiple Samples

samples = adc.samples(n=10, type='voltage', delay=0.01)
print(samples)
  • n: number of samples
  • type: raw, voltage, or real
  • delay: seconds between samples

6. Asynchronous Sampling

samples = await adc.async_samples(n=10, type='real')
print(samples)

7. Mean Value

avg = adc.mean(n=10, type='voltage')
print(f"Average voltage: {avg:.2f} V")
  • Use async_mean for asynchronous calculation.

Pin Connection Check

8. Check if Pin is Connected

connected, info = adc.is_pin_connected(n=20, delay=0.001)
print(connected, info)
  • Returns a boolean and a dictionary with details.
  • Detects floating, short-to-GND, or short-to-VCC conditions.

9. Asynchronous Check

connected, info = await adc.async_is_pin_connected(n=20)
print(connected, info)

Notes & Tips

  • Use voltage() for direct voltage readings.
  • Use real() for calibrated real-world measurements.
  • Sampling with delay improves stability.
  • Connection heuristics help avoid unreliable readings.

External Resources

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