nRF52840 microcontroller, in a pro-micro footprint, inspired by the nRFMicro and nice!nano.
- VDDH power path (5V USB power, and/or 3.7V Li-ion battery)
- software controllable battery charge current (off, ~100mA, ~250mA, ~350mA)
- ESD protection on USB lines, and 500mA fuse protection for VBUS and EXT_5V
- "Bidirectional" power over EXT_5V
Note that the project files use kicad nightly (5.99).
The EXT_5V pin acts both as a power input and a power output; normally it is an input. When VBUS is high (ie. USB is connected), it will output VBUS (minus a schottky drop, ~0.3V).
EXT_5V is connected to the battery charger, so if you wire your TRRS (for split keyboards) to it (instead of a 3.3V VCC line), you can charge the battery on both halves by only plugging in one half to USB.
The PCB should be manufactured with an ENIG surface finish, but it can be done using HASL (in which case you should run a solder wick over all the pads first).
All components are 0402 (1005 metric) or larger, and can be placed by hand without magnification. A stencil is mandatory — get a 100µm (0.1mm) thick one.
There's no "component silkscreen" on the board except 4 lines to align the nRF chip, so using something like KiCad's Interactive BOM plugin is a good idea.
It's a good idea to get an electropolished stencil if you want to paste more than one board at a time, if not you will probably need to completely clean out the stencil before pasting another board.
I used Chipquik SMD291AX T4 paste for all the boards.
There are no known problems from revision 5.17 onwards. 5.19 and 5.20 are just minor tweaks to the inner ground plane and the paste layer, so the functionality remains identical.
Licensed under the Apache 2.0 license, see LICENSE.
If you encounter any problems, feel free to open an issue on this repo. However, I am not obligated to provide any support, and you undertake any assembly/manufacturing/purchasing at your own risk.
on an AS IS BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE.
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