Gauging interest in a DM48 or DM50?

[JohnHind]

Seems to me this would be a lot easier if we did not need to have a fixed key layout with tooling costs per design, but different layouts could be swapped in and out of the same basic calculator frame as easily as firmware can be changed. It is now possible to get PCBs made from CAD files in very low volumes very cheaply (effectively zero tooling cost). Some makers have used this to produce 'PCB Art' and these techniques could be adapted to produce key label artwork. Until recently, this would be limited to one colour (the 'silk screen' layer on the PCB) plus gold (plated copper layer), but recently full colour screening has become available.

One problem is you cannot have markings on the key top only on the surround (like an overlay). One way round this is to use 'tactile buttons' with small round actuators that stand proud through holes in the PCB plane. Although the button is very small, it feels quite good because it clicks in flush with the PCB surface and does not feel harsh.

It is possible to use two parallel PCB planes with one forming the legend surface and the other the matrix wiring and mounting for the switches, but recently I discovered 'reverse mount tactile switch buttons' (for example, from Adafruit). These solder to one side of a PCB with the actuator on the bottom protruding through a hole in the same PCB, so the artwork would be on the other side.

With this approach, it would be possible to produce low volume customisations which changed both the legends and also the number and layout of the keys. The customer could easily experiment with different 'personalities' without having to buy a complete new calculator or compromise the layout to use a design intended for a different personality. Ambitious end users would even be able to design their own layouts using programability and layout customisation features in a particular firmware.