QT Py (SAMD based)

Two Manufacturers (SAMD21)

• Adafruit QT Py SAMD21 Product Page
• Seeeduino XIAO

Features

• ATSAMD21E18 32-bit Cortex M0+ version
  • 48 MHz, 32-bit processor
  • 256KB Flash
  • 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.
• 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 AP2112, 600mA peak output
• Reset switch for starting your project code over or entering bootloader mode
• USB Type C connector

Optional External Flash (Adafruit QT Py Only)

• Optional 2 MB SOIC-8 SPI Flash chip on bottom
  • Can't use castellated pins if Flash on bottom is installed
  • GD25Q16
• Access the SPI flash in Arduino on SPI1 and chip select pin 17
• In CircuitPython, a 'haxpress' version of the runtime will need to be installed, so it knows to look for the larger filesystem
  • There is more hardware support in the haxpress CircuitPython build because Adafruit added more code to the internal flash instead of using it for a filesystem
  • Built-in modules available: adafruit_pixelbuf, analogio, audiobusio, audiocore, audioio, board, busio, digitalio, displayio, errno, fontio, math, microcontroller, neopixel_write, nvm, onewireio, os, paralleldisplay, pulseio, pwmio, rainbowio, random, rotaryio, rtc, storage, struct, supervisor, terminalio, time, touchio, traceback, usb_cdc, usb_hid, usb_midi

Links

• Adafruit QT Py CircuitPython page
• Adafruit Learning System for QT Py
• Getting Started with Seeeduino XIAO
• CircuitPython on Seeeduino XIAO
  • Seeeduino XIAO CircuitPython Download

Pins

Adafruit SAMD Pinout

(Click on image for larger file)

Seeed Studio SAMD Pinout

3V

• Regulated output from the onboard regulator. You can draw 500mA

5V

• 5v out from the USB port.
• Voltage input
  • Requires external diode
    • Schottky, signal, power
    • Between external power source and this pin
    • Cannot power the USB port by supplying 5V to this pin
      • There is a protection diode that prevents the 5V from reaching the USB connector.
      • This is to protect host computer USB ports, etc.

A0 / D0 - Digital/analog GPIO pin 0

• Digital I/O 0
• Analog In 0
• True analog output with 10 bit precision
• Does not have PWM
• Capacitive touch input.

A1 / D1 - Digital/analog GPIO pin 1

• Digital I/O 1
• Analog In 1
• Capacitive touch input
• AREF pin.

A2 / D2 - Digital/analog GPIO pin 2

• Digital I/O 2
• Analog In 2
• PWM
• Capacitive touch input.

A3 / D3 - Digital/analog GPIO pin 3

• Digital I/O 3
• Analog In 3
• PWM output
• Capacitive touch input.

SDA / D4

• Digital I/O 4
• I2C SDA pin
• PWM output
• No analog on this pin
• No pull up on this pin
• When using with I2C requires an external 2.2K-10K pullup to 3.3V.

SCL / D5

• Digital I/O 5
• I2C SCL
• No analog on this pin
• No pull up on this pin
• When using with I2C requires an external 2.2K-10K pullup to 3.3V.

TX / A6 / D6

• Digital I/O 6
• Transmit (output) for Serial1
• Analog 6
• PWM output
• Capacitive touch input

RX / A7 / D7

• Digital I/O 7
• Receive (input) for Serial1
• Analog 7
• PWM output
• Capacitive touch input

SCK / A8 / D8

• Digital I/O 8
• SPI SCK pin
• Analog 8
• PWM output

MISO / A9 / D9

• Digital I/O 8
• SPI MISO pin
• Analog 8
• PWM output

MOSI / A10 / D10

• Digital I/O 10
• SPI MOSI pin
• Analog 10
• PWM output

NeoPixel

• Connected to digital pin 11 for signal
• Set pin 12 low for low power usage
• By default pin 12 is set high by Arduino/CircuitPython
• Code example

import board
import neopixel

pixels = neopixel.NeoPixel(board.NEOPIXEL, 1)
# fill((rVal, gVal, bVal))
# rVal, gVal, bVal = red/green/blue values (0-255)
pixels.fill((255, 0, 0))  # Note double parens

Programming

• C/C++ or CircuitPython

C/C++

• Arduino IDE Setup
  • Requires Arduino IDE version 1.8 or higher
  • Add https://adafruit.github.io/arduino-board-index/package_adafruit_index.json to Preferences Additional Boards Manager URLs
  • Add Adafruit SAMD Boards in Boards Manager

CircuitPython/MicroPython

CircuitPython for SAMD

• Adafruit CircuitPython 7.3.0 on 2021-01-21
  • CircuitPython is a derivative of MicroPython
  • CircuitPython looks for a code file on the board to run
    • There are four options: code.txt, code.py, main.txt and main.py
    • CircuitPython looks for those files, in that order, and then runs the first one it finds
  • QT_Py_blink.py
  • QT Py Haxpress used with 2MB Flash EEPROM
• Mu code editor
• Free memory
  • Reports 17,776 bytes of free space

import gc
gc.mem_free()

Updating CircuitPython

• Save the contents of CIRCUITPY, just in case
• Double-click the reset button to show the BOOT drive
• Drag the update-bootloader .uf2 file to the BOOT drive
• Wait a few tens of seconds for the bootloader to update; the BOOT drive will reappear
• Check INFO_UF2.TXT to verify that the bootloader version has been updated. Then you will need to reload CircuitPython.
• Update mpy files

Land Boards CircuitPython Code

• I2C scanner

I2CIO-8 (MCP23008) Drivers

• GitHub Repo
  • I2CIO8.py Demo code - Bounce an LED across MCP23008 card output pins
  • I2CIO8_RW.py - Read jumpers, write back LEDs

SWLEDX8-I2C (MCP23017) Drivers

• SWLEDX8.py = Control the SWLEDX8-I2C card

PROTO16-I2C (MCP23017) Drivers

• PROTO16_Blink.py - Control the PROTO16-I2C card

Digital I/O Example

import board
import digitalio
import time

led = digitalio.DigitalInOut(board.D13)
led.direction = digitalio.Direction.OUTPUT

while True:
    led.value = True
    time.sleep(0.1)
    led.value = False
    time.sleep(0.5)

Flash EEPROM 2 MB

QT Py Breakout Board

• Built onto GRID49 card
• Socket for QT Py
• QT Py pins brought to header strips
• 3.3V power distribution on 2x8 header

Pins (CCW direction)

• S12 = A0
• R12 = A1
• Q12 = A2
• P12 = A3
• N12 = SDA
• M12 = SCL
• L12 = TX
• L1 = RX
• M1 = SCK
• N1 = MI
• P1 = MO
• Q1 = 3.3V
• R1 = GND
• S1 = 5V
• A6=B6=C6=D6=E6=F6=G6=H6 = GND
• A7=B7=C7=D7=E7=F7=G7=H7 = 3.3V

QTPy49 Board

• QTPy49