Adafruit Feather m4 express User manual

Adafruit Feather M4 Express

Created by lady ada

Last updated on 2019-03-04 10:41:14 PM UTC

Overview

It's what you've been waiting for, the Feather M4 Express featuring ATSAMD51. This Feather is fast like a swift, smart

like an owl, strong like a ox-bird (it's half ox, half bird, OK?) This feather is powered by our new favorite chip, the

ATSAMD51J19 - with its 120MHz Cortex M4 with floating point support and 512KB Flash and 192KB RAM. Your code

will zig and zag and zoom, and with a bunch of extra peripherals for support, this will for sure be your favorite new

chipset.

And best of all, it's a Feather - so you know it will work with all our FeatherWings! What a great way to quickly get up

and running.

The most exciting part of the Feather M4 is that while you can use it with the Arduino IDE - and it's bonkers fast when

you do, we are shipping it with CircuitPython on board. When you plug it in, it will show up as a very small disk drive

with main.py on it. Edit main.py with your favorite text editor to build your project using Python, the most popular

programming language. No installs, IDE or compiler needed, so you can use it on any computer, even ChromeBooks or

computers you can't install software on. When you're done, unplug the Feather and your code will go with you.

Here are some of the updates you can look forward to when using Feather M4:

Measures 2.0" x 0.9" x 0.28" (51mm x 23mm x 8mm) without headers soldered in

Light as a (large?) feather - 5 grams

ATSAMD51 32-bit Cortex M4 core running at 120 MHz, 32-bit, 3.3V logic and power

Hardware DSP and floating point support

512 KB flash, 192 KB RAM

2 MB SPI FLASH chip for storing files and CircuitPython code storage.

No EEPROM

32.768 KHz crystal for clock generation & RTC

3.3V regulator with 500mA peak current output

USB native support, comes with USB bootloader and serial port debugging

Built in crypto engines with AES (256 bit), true RNG, Pubkey controller

Tons of GPIO! 21 x GPIO pins with following capabilities:

Dual 1 MSPS 12 bit true analog DAC (A0 and A1) - can be used to play 12-bit stereo audio clips

Dual 1 MSPS 12 bit ADC (6 analog pins some on ADC1 and some on ADC2)

6 x hardware SERCOM - Native hardware SPI, I2C and Serial all available

16 x PWM outputs - for servos, LEDs, etc

I2S input and output

8-bit Parallel capture controller (for camera/video in)

Built in 100mA lipoly charger with charging status indicator LED

Pin #13 red LED for general purpose blinking

Power/enable pin

4 mounting holes

Reset button

The Feather M4 Express uses the extra space left over to add a Mini NeoPixel, 2 MB SPI Flash storage and a little

prototyping space. You can use the SPI Flash storage like a very tiny hard drive. When used in CircuitPython, the 2 MB

flash acts as storage for all your scripts, libraries and files. When used in Arduino, you can read/write files to it, like a

little datalogger or SD card, and then with our helper program, access the files over USB.

Easy reprogramming: the Feather M4 comes pre-loaded with the UF2 bootloader (https://adafru.it/vQd), which looks

like a USB storage key. Simply drag firmware on to program, no special tools or drivers needed! It can be used to load

up CircuitPython or Arduino IDE (it is bossa-compatible)

Comes fully assembled and tested, with the UF2 USB bootloader. We also toss in some headers so you can solder it in

and plug into a solderless breadboard.

Pinouts

The Feather M4 is chock-full of microcontroller goodness. There's also a lot of pins and ports. We'll take you a tour of

them now!

Power Pins

GND - this is the common ground for all power and logic

BAT - this is the positive voltage to/from the JST jack for the optional Lipoly battery

USB - this is the positive voltage to/from the micro USB jack if connected

EN - this is the 3.3V regulator's enable pin. It's pulled up, so connect to ground to disable the 3.3V regulator

3V - this is the output from the 3.3V regulator, it can supply 500mA peak

Logic pins

This is the general purpose I/O pin set for the microcontroller.

All logic is 3.3V

Nearly all pins can do PWM output

All pins can be interrupt inputs

#0 / RX - GPIO #0, also receive (input) pin for Serial1 (hardware UART). Also PWM out

#1 / TX - GPIO #1, also transmit (output) pin for Serial1. Also PWM out

SDA - the I2C (Wire) data pin. There's no pull up on this pin by default so when using with I2C, you may need a

2.2K-10K pullup. Also PWM out

SCL - the I2C (Wire) clock pin. There's no pull up on this pin by default so when using with I2C, you may need a

2.2K-10K pullup. Also PWM out

#4 - GPIO #4, PWM out

#5 - GPIO #5, PWM out

#6 - GPIO #6, PWM out

#9 - GPIO #9, PWM out

#10 - GPIO #10, PWM out

#11 - GPIO #11, PWM out

#12 - GPIO #12, PWM out

#13 - GPIO #13, PWM out and is connected to the red LED next to the USB jack

SCK/MOSI/MISO - These are the hardware SPI pins, you can use them as everyday GPIO pins (but recommend

keeping them free as they are best used for hardware SPI connections for high speed.)

Analog Pins:

A0 - This pin is analog

input

A0 but is also an analog

output

due to having a DAC (digital-to-analog converter).

You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output

A1 - This pin is analog

input

A1 but is also an analog

output

due to having a DAC (digital-to-analog converter).

This is the second DAC, and is 'independent' of A0. You can set the raw voltage to anything from 0 to 3.3V,

unlike PWM outputs this is a true analog output. Also can do PWM.

A2 thru A5 - These are each analog input as well as digital I/O pins. These pins can also do PWM.

These pins are available in CircuitPython under the board module. Names that start with # are prefixed with D and

other names are as is. So #0 / RX above is available as board.D0 and board.RX for example.

Parallel Capture Peripheral

There's a 'camera' input peripheral you can use with some camera chips to capture video with 8-bit data width. We

thought this was neat so we made sure all those pins were available. Here are the PCC pins (left) and the Feather M4

pins it's mapped to. Unlike other peripherals, you cannot mux these signals to other pins!

DEN1: SDA

DEN2: SCL

CLK: D6

D0: D11

D1: D13

D2: D10

D3: D12

D4: MISO

D5: D5

D6: MOSI

D7: SCK

QSPI Flash and NeoPixel

As part of the 'Express' series of boards, the Feather M4 Express is designed for use with CircuitPython. To make that

easy, we have added two extra parts to this Feather M4: a mini NeoPixel (RGB LED) and a 2 MB QSPI (Quad SPI) Flash

chip

The NeoPixel is connected to pin #8 in Arduino, so just use our NeoPixel library (https://adafru.it/dhw) and set it up as a

single-LED strand on pin 8. In CircuitPython, the NeoPixel is board.NEOPIXEL and the library for it is

here (https://adafru.it/wby) and in the bundle (https://adafru.it/uap). The NeoPixel is powered by the 3.3V power supply

but that hasn't shown to make a big difference in brightness or color. The NeoPixel is also used by the bootloader to

let you know if the device has enumerated correctly (green) or USB failure (red). In CircuitPython, the LED is used to

indicate the runtime status.

The QSPI Flash is connected to 6 pins that are not brought out on the GPIO pads. This way you don't have to worry

about the SPI flash colliding with other devices on the main SPI connection.

QSPI is neat because it allows you to have 4 data in/out lines instead of just SPI's single line in and single line out. This

means that QSPI is

at least

4 times faster. But in reality is at least 10x faster because you can clock the QSPI peripheral

much faster than a plain SPI peripheral

However, the QSPI port is

not

also on an SERCOM. So, you have to either use the QSPI peripheral or bitbang SPI if you

want to talk to the chip. We have an Arduino library here which provides QSPI interfacing for

Arduino (https://adafru.it/BeX). In CircuitPython, the QSPI flash is used natively by the interpretter and is read-only to

user code, instead the Flash just shows up as the writeable disk drive!

Other Pins!

RST - this is the Reset pin, tie to ground to manually reset the ATSAMD51, as well as launch the bootloader

manually

ARef - the analog reference pin. Normally the reference voltage is the same as the chip logic voltage (3.3V) but if

you need an alternative analog reference, connect it to this pin and select the external AREF in your firmware.

Can't go higher than 3.3V!

Debugging Interface

If you'd like to do more advanced development, trace-debugging, or not use the bootloader, we have the SWD

interface exposed. You'll have to solder to the two SWD/SWCLK pads on the bottom:

On the Feather M4, at least for now, AREF is tied to 3.3V due to a silicon v0 bug that does not allow the DACs

to work unless AREF is connected to 3.3V. You cut the bottom jumper if you need a different AREF voltage

but note that this may change DAC range!



Assembly

We ship Feathers fully tested but without headers attached - this gives you the most flexibility on choosing how to use

and configure your Feather

Header Options!

Before you go gung-ho on soldering, there's a few options to consider!

The first option is soldering in plain male headers, this

lets you plug in the Feather into a solderless

breadboard

Another option is to go with socket female headers. This

won't let you plug the Feather into a breadboard but it

will let you attach featherwings very easily

We also have 'slim' versions of the female headers, that

are a little shorter and give a more compact shape

Finally, there's the "Stacking Header" option. This one is

sort of the best-of-both-worlds. You get the ability to

plug into a solderless breadboard

and

plug a

featherwing on top. But its a little bulky

Soldering in Plain Headers

Prepare the header strip:

Cut the strip to length if necessary. It will be easier to

solder if you insert it into a breadboard - long pins down

Add the breakout board:

Place the breakout board over the pins so that the short

pins poke through the breakout pads

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to

Excellent Soldering

(https://adafru.it/aTk)

Solder the other strip as well.

You're done! Check your solder joints visually and

continue onto the next steps

Soldering on Female Header

Tape In Place

For sockets you'll want to tape them in place so when

you flip over the board they don't fall out

Flip & Tack Solder

After flipping over, solder one or two points on each

strip, to 'tack' the header in place

And Solder!

Be sure to solder all pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to

Excellent Soldering

(https://adafru.it/aTk)

You're done! Check your solder joints visually and

continue onto the next steps

Power Management

Battery + USB Power

We wanted to make the Feather easy to power both when connected to a computer as well as via battery. There's two

ways to power a Feather. You can connect with a MicroUSB cable (just plug into the jack) and the Feather will regulate

the 5V USB down to 3.3V. You can also connect a 4.2/3.7V Lithium Polymer (Lipo/Lipoly) or Lithium Ion (LiIon) battery

to the JST jack. This will let the Feather run on a rechargable battery. When the USB power is powered, it will

automatically switch over to USB for power, as well as start charging the battery (if attached) at 100mA. This happens

'hotswap' style so you can always keep the Lipoly connected as a 'backup' power that will only get used when USB

power is lost.

The JST connector polarity is matched to Adafruit LiPoly batteries. Using wrong polarity batteries can destroy

your Feather



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