UART
4 pages across tutorials, modules, pinouts and guides.
RS485 Transceiver Boards: MAX485 for 5 V and MAX3485 for 3.3 V
Two RS485 boards from one 12-pack: a MAX485 board for 5 V microcontrollers and a MAX3485 board for 3.3 V ones. The six pins, which board goes with your microcontroller, the 120 Ω fitted on every board that only the two end boards should keep, and RE joined to DE so one pin sets the direction.
58mm Thermal Printers: the receipt kit, the label kit and the USB-C base board
Two thermal printer kits that share one Type-C TTL base board. The 9 V a USB port will not give you, which header your microcontroller belongs on, the baud rate printed on each unit, and the commands that put text, barcodes and labels on paper.
Logic Level Converters: MOSFET 2/4/6-Channel, TXB0108 and TXS0108
Five boards that let a 3.3 V board and a 5 V part share a wire safely. Which one to use for I²C, SPI, serial or an LED strip, which side is which, and the three wires that come before any signal.
Logic Analyzer Kit, 8-Channel 24 MHz
Eight channels sampled at up to 24 MS/s, straight up a USB cable. It decodes I²C, UART and SPI at the speeds a microcontroller actually runs, and the sample rate is the number that decides the rest.