2 hours
I researched the different parts that are going to be used in the PCB.
For the chip, I opted for the nRF52833, which is commonly used for wireless keyboard builds. I could have with a nice!nano, which also uses a similar nRF, but I wanted to go for a bare chip to have a single PCB. However, this also means that I have to consider how I’m setting up the USB port and integrated battery charger.
The charger is the TP4057, which I also used in a previous project. With the USB port, I’ll have it connected it to the battery to allow for charging when a cable is connected. The USB port itself is also pretty standard, just a 14-pin USB-C.
However, what took the most time was just finding the specific parts for each of these. The nRF layout I’m using is the QDAA-R, which has exposed pads on the edges of the chip. I’ve soldered gull-wing style packages before, which feel a lot more reasonable since you can see the connections, but the nRF (and a lot of other similar chips) don’t come in the QFP layout, so I had to opt for this.
However, this also means that I’m a bit more limited in the multiplexing layout, since there are less pins to work with. I’m thinking of a 40% design, which would work with 12 columns and 4 rows, meaning 48 keys (although some rearranging will have to take place since the max columns is 14 keys, rather than 12).