Ergonomic keyboard project, here’s the core mainboard that connects to the previously shared keyboard PCB.
This board acts as the brain of the setup and includes:
■ The nRF52840 BLE 5 chipset from Nordic for wireless communication.
■ 8GB eMMC memory from Samsung for file storage.
■ A power management system with a Texas Instruments BQ25 series battery charger and path-management IC.
The board uses a 4-layer stackup with FR4 as the core material, an ENIG finish, and tented vias.
One challenge worth mentioning is that the nRF52840 BGA package requires a 4-layer design to properly access the inner rows of the BGA pads. This means using 0.18mm vias, which increases manufacturing complexity and costs. In a simpler setup, accessing those pins wouldn’t be necessary since most of the easily routable BGA pads can be managed with a 2-layer board instead of requiring a 4-layer one.
