Components Used in the Project

• E73 nRF52840 *1
• 16-pin Mid-mount USB-C *1
• 100K 0603 Resistor *1
• 5.1K 0603 Resistor *2
• 1K 0603 Resistor *2
• 10K 0603 Resistor *1
• 820K 0603 Resistor *1
• 2M 0603 Resistor *2
• 1N5819 *1
• 0603 LED *2
• AO3407 *2
• AP2112K-3.3 *1
• TP4054 *1
• 32.768 kHz 1610 Crystal *1

Description

Pro Micro-compatible Bluetooth 5.2 board with Li-Po charger and USB-C (nRF52840-based) The board is based on the BLE-Micro-Pro board and nrf52 QMK firmware branch by sekigon-gonnoc. I've made my version using the cheapest nRF52840 bluetooth module available and the cheapest available components instead of rare japanese ones. I've also added Li-Po charger, USB Type-C and a physical ON/OFF switch on board. There's almost no room on a board this size so I had to remap GPIO pins to the closest physical positions. The rest is taken from the Adafruit Feather schematic almost verbatim, considering that modules I use have different layout and different set of pins. 1.4 is a very new board, made in collaboration with Ariamelon. It is compatible with 1.3 firmware, but also has Crystal, full USB/SWD pinout and other improvements: charger and power pins pulled down to avoid floating, added charging LED and removed software charging current control, so less code needed (for that you may build nRFMicro 1.3, it's a bit cheaper). nRFMicro Features: * Built in KiCad and fully autorouted with Freerouting (shouldn't be a problem to modify) * Same size as Pro Micro (18x33mm), has both MicroUSB and Type-C, Li-Po charger and BT 5.0 * Runs full-featured QMK software (nrf52 fork), uses USB Mass Storage for firmware updates * Runs fully wireless split keyboards over Bluetooth, does NOT need TRRS cables or receivers * Supports wired split keyboards via USB-C, MicroUSB and I2C/Serial extension cables FAQ * Do you sell them? No. It's a DIY project for kids. It's NOT suitable for mass production. See PCBA and Alternatives. * Do I still need TRRS cable for the wireless split keyboard? No, it uses wireless link between the halves. Cables are supported too (no charging over TRRS though). * What's the battery life? 2 weeks on a 100 mAh battery, a year on a 2500 mAh battery (2xAA). Charger is built in. * Is there a lag while typing? BLE devices can reach a latency of 1.3 ms, so no, there's virtually no lag. * Can it switch between bluetooth devices? Both QMK and ZMK support at least up to 5 bluetooth profiles. Advanced FAQ: * Why there are no capacitors on the board (in the latest revisions)? No room. It reuses capacitors from the bluetooth module (there are two large 4.7uF ones). * Why the board is single sided, is it for the automated assembly? It's NOT automated assembly compatible at all. It's just trying to be as thin as Pro Micro. * I'm designing my keyboard specifically for your controller, where to get footprints? Please stop. This board is nothing but a drop-in Pro Micro replacement, use Pro Micro footprints. * What are the EXT_VCC and EXT_GND? Are they the same pins as VCC and GND? Yes. Power output is sofware-controlled to save battery (RGB LEDs draw up to 1 mA each when off). * What are you using to render pictures for GitHub? I am using kicadScripts both for pictures and gerbers. Project wiki: https://github.com/joric/nrfmicro/wiki