mosfet - Open Drain Serial TX output on Arduino - Electrical Engineering Stack Exchange
Nano-sized LiPo Charger for Teensy from Hyperbolic_Labs on Tindie
Teensy 3.5 without pins, 6 Serial Ports (2 with FIFO and Fast Baud Rates) 3 SPI Ports (1 with FIFO) 3 I2C Ports Real-Time Clock By Brand PJRC - Walmart.com