This example shows you how you can use the DAC (Digital to Analog Converter).

In the example below, click theDownload Project Bundle button below to download the necessary libraries and thecode.py file in a zip file. Extract the contents of the zip file, open the directoryCircuitPython_Essentials/CircuitPython_AnalogOut/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to yourCIRCUITPY drive.

YourCIRCUITPY drive should now look similar to the following image:

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Analog Out example"""import boardfrom analogio import AnalogOutanalog_out = AnalogOut(board.A0)while True:    # Count up from 0 to 65535, with 64 increment    # which ends up corresponding to the DAC's 10-bit range    for i in range(0, 65535, 64):        analog_out.value = i

# SPDX-FileCopyrightText: 2018 Kattni Rembor for Adafruit Industries## SPDX-License-Identifier: MIT"""CircuitPython Analog Out example"""import boardfrom analogio import AnalogOutanalog_out = AnalogOut(board.A0)while True:    # Count up from 0 to 65535, with 64 increment    # which ends up corresponding to the DAC's 10-bit range    for i in range(0, 65535, 64):        analog_out.value = i

Creating an analog output

analog_out = AnalogOut(A0)

Creates an objectanalog_out and connects the object toA0, the only DAC pin available on both the M0 and the M4 boards. (The M4 has two, A0 and A1.)

Setting the analog output

The DAC on the SAMD21 is a 10-bit output, from 0-3.3V. So in theory you will have a resolution of 0.0032 Volts per bit. To allow CircuitPython to be general-purpose enough that it can be used with chips with anything from 8 to 16-bit DACs, the DAC takes a 16-bit value and divides it down internally.

For example, writing 0 will be the same as setting it to 0 - 0 Volts out.

Writing 5000 is the same as setting it to 5000 / 64 = 78, and 78 / 1024 * 3.3V = 0.25V output.

Writing 65535 is the same as 1023 which is the top range and you'll get 3.3V output

Main Loop

The main loop is fairly simple, it goes through the entire range of the DAC, from 0 to 65535, but increments 64 at a time so it ends up clicking up one bit for each of the 10-bits of range available.

CircuitPython is not terribly fast, so at the fastest update loop you'll get 4 Hz. The DAC isn't good for audio outputs as-is.

Express boards like the Circuit Playground Express, Metro M0 Express, ItsyBitsy M0 Express, ItsyBitsy M4 Express, Metro M4 Express, Feather M4 Express, or Feather M0 Express have more code space and can perform audio playback capabilities via the DAC. QT Py M0, Gemma M0 and Trinket M0 cannot!

Check outthe Audio Out section of this guide for examples!

Find the pin

Use the diagrams below to find the A0 pin marked with a magenta arrow!