Adafruit QT Py - SAMD21 Dev Board

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Lorenzo von Matterhorn
Jan 31, 2009
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Out of stock which is the usual for them with new products.

Adafruit QT Py - SAMD21 Dev Board

Same size, form-factor, and pin-out as Seeed Xiao [which I never knew about until Adafruit pretty much copied it with some improvements]
ATSAMD21E18 32-bit Cortex M0+ - 48 MHz 32 bit processor with 256KB Flash and 32 KB RAM
Native USB supported by every OS - can be used in Arduino or CircuitPython as USB serial console, MIDI, Keyboard/Mouse HID, even a little disk drive for storing Python scripts.
Can be used with Arduino IDE or CircuitPython
Built in RGB NeoPixel LED
11 GPIO pins:
True analog output on one I/O pin - can be used to play 10-bit quality audio clips in Arduino (CircuitPython does not have storage for audio clips)
9 x 12-bit analog inputs (SDA/SCL do not have analog inputs)
1 x Optional AREF on A1
9 x PWM outputs (A0 is analog out, A1 is not PWM capable)
Hardware I2C port with STEMMA QT plug-n-play connector
Hardware UART
Hardware SPI
Hardware I2S
6 x Capacitive Touch with no additional components required
3.3V regulator with 600mA peak output
Optional SOIC-8 SPI Flash chip on bottom
Reset switch for starting your project code over or entering bootloader mode
USB Type C connector
Really really small

The Seeed XIAO:



New Member
Jan 4, 2015
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The pads on the back also work with SPI bus FRAM chips since the pinouts are the same. I did a 2-channel layout of a baro-only altimeter with logging to a 2Mbit FRAM which gives enough for several flights. Decimating logs during descent makes it last much longer. No flights yet but the same code base and electronics are working well on other Arduino platforms.

Lovely little "Arduino" boards! I can post pix of some altimeters I made using QtPy and xiao.


Well-Known Member
TRF Supporter
Jul 10, 2007
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Melbourne Australia
Its good to see FRAM replacing flash memory. Much greater number if write cycles, by up to 8 orders of magnitude or so.

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