DAC — pymcu.hal.dac#
from pymcu.hal.dac import DACPin
Digital-to-analog output: a pin that drives a voltage, the mirror of pymcu.hal.adc, which reads one.
class DACPin#
DACPin(pin)#
Claims the pin and powers up the converter behind it.
No part PyMCU targets today has one. The constructor refuses where it is written and
names what does work on that part. That refusal is the point of the module: before it,
analogio.AnalogOut built with a warning and compiled the assignment to nothing, so a
program that asked for an analog output ran and drove no pin.
Family |
Answer |
|---|---|
AVR |
Refused. No AVR part has a converter. |
PIC12 / PIC14 |
Refused. |
PIC18 |
Refused. The PIC18F45K50’s 5-bit reference DAC feeds the comparators, not a pin. |
RP2040 / RP2350 |
Refused. |
Methods#
Method |
Return type |
Description |
|---|---|---|
|
— |
Drive the pin at |
|
— |
Release the pin |
What to use instead#
For an analog-like output on a part with no converter, filter a PWM wave:
from pymcu.hal.pwm import PWM
out = PWM("PD6", freq=62500, duty_u16=32768) # half the supply after the filter
out.set_duty_u16(49152) # three quarters
A first-order RC on the pin turns the square wave into a level. Pick the corner well below the PWM frequency: at 62.5 kHz, 10 kΩ and 100 nF (160 Hz corner) leaves a few millivolts of ripple. The trade is bandwidth — the output follows changes no faster than the filter.
Where a real converter is required (audio, precision references), drive an external one over SPI or I2C.
Adding a part that has one#
A new branch in DACPin.__init__ plus a chip module with dac_init and dac_write_u16.
Nothing above pymcu/hal/dac.py changes: the compatibility layers speak set_value_u16
and never learn the part’s resolution.