PJRC boards
1 PJRC development board — pinouts, specs, and datasheets.
Teensy 4.0
board
PJRC · i.MX RT1062 (Cortex-M7 600MHz)
PJRC's Teensy 4.0 is a tiny, very fast Arduino-compatible board (600 MHz Cortex-M7). 24 digital pins around the edge (14 with analog inputs), multiple hardware serial/SPI/I2C, and USB. 3.3V logic (NOT 5V tolerant).