class ADCAll – access all ADC channels¶

ADCAll exposes every ADC channel on the MCU through a single object – both the external analog-input pins and the internal channels for die temperature, the 1.21 V reference and VBAT. It is useful for monitoring the MCU’s supply rail and on-chip sensors without instantiating an ADC per pin.

Example:

import pyb

# 12-bit resolution, internal channels only (temp + VBAT + VREF).
adcall = pyb.ADCAll(12, 0x70000)
temp = adcall.read_core_temp()
vbat = adcall.read_core_vbat()
vref = adcall.read_core_vref()
vdda = adcall.read_vref()

Constructors¶

class pyb.ADCAll(resolution: int, mask: int = 0xffffffff)¶

Provides simultaneous access to every ADC channel on the MCU, including the internal channels for die temperature, the internal 1.21 V reference, and VBAT. Constructing this object switches all masked external ADC pins to analog-input mode.

resolution is the ADC conversion resolution in bits (typically 8, 10 or 12).
mask is a 32-bit bitmask selecting which channels to enable; bit N enables channel N. Defaults to 0xffffffff (all channels). The internal channels live at bits 16 (temperature), 17 (VBAT) and 18 (VREF), so to enable only the internal channels pass 0x70000.

The on-chip temperature sensor is factory calibrated and accurate to roughly ±1 °C, but it measures the die temperature – which is typically tens of degrees above ambient when the MCU is active. Readings are only meaningful as a proxy for ambient on a freshly woken board.

Warning

Analog input voltages must never exceed the actual supply voltage.

Methods¶

read_channel(channel: int) → int¶: Read the given ADC channel. External channels (0 – 15) return unscaled raw values at the configured resolution; the internal channels (16–18) return raw values too, but the dedicated helpers below convert them to voltages.

read_core_temp() → float¶: Return the on-die temperature in degrees Celsius, computed from the internal temperature channel and the factory calibration values stored in the MCU.

read_core_vbat() → float¶: Return the backup-battery voltage in volts. The reading is taken through an on-chip voltage divider (so the headroom does not restrict the ADC’s input range) and scaled back to the actual battery voltage. The divider is only active during the ADC conversion, so the standby drain on the backup battery is negligible.

read_core_vref() → float¶: Return the internal 1.21 V (nominal) reference voltage in volts, measured with the MCU supply as the ADC reference. This is the raw conversion result.

read_vref() → float¶: Return the MCU supply voltage in volts. Computed by measuring the internal voltage reference and back-scaling using its factory calibration value. With a healthy 3.3 V rail the reading will be close to 3.3. The MCU continues to operate – and ADC conversions remain meaningful – with a supply as low as around 2 V, provided the appropriate MCU clock, flash access speed and programming-mode settings are observed.