|Developer||Fredrik Atmer bpiphany|
|Features||A modular keyboard with symmetric stagger.|
DescriptionThe Blue Pill PCB was designed to test how well it would work using a serial protocol to read keys and light LEDs. The main idea is that it would be easy to build an input device consisting of several modules by simply daisy chaining them. Reflecting that there is no on-board controller, and no location to mount any specific controller board. There is a 6-pin (plus VCC and GND) serial interface to add any controller circuit of choice. The PCB fits into the Poker case.
One pin of the key switches is connected to one individual input pin on a 74hc165 shift register. Each input pin has an external pull-up resistor in a resistor network shared with three other inputs.
There are LED solder pads for all switch location. 21 of them are connected to a single TLC5947 LED driver. It is a serial communication chip with 24 LED outputs, and 12-bit PWM on each channel.
The layout options are symmetric. Because of this there is a "gap" in the home row. This gap can be placed in the absolute center or offset one key to the left for a more traditional layout. The space bar configurations also reflects the symmetric idea. There are a couple of options both for the symmetric and the offset layouts. Backspace splits into two separate keys. Left and right shift splits as well. For the offset layouts a 2.25 unit return can be chosen, with a 3 unit shift (or 2+1 unit).