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. . This feather is powered by our new chip, the ATSAMD51J19 - with its 120MHz Cortex M4 with floating point support and 512KB Flash and 192KB RAM. The Feather M4 comes pre-loaded with the UF2 bootloader, 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)

Specifications:

Measures 2.0" x 0.9" x 0.28" (50.8mm x 22.8mm x 7mm) without headers soldered in
Light as a feather - 5 grams
ATSAMD51 32-bit Cortex M4 core running at 120 MHz, 32-bit, 3.3V logic and power
Floating point support with Cortex M4 DSP instructions
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