Buttons and Layout

Published on 2019-04-18 in PewPew M4.

With the display tentatively chosen (we will see how well that one works, and if it doesn’t, there are many other possibilities) I have started to look into adding all the rest of components and arranging them. The second biggest part, and one with which the user will have intimate contact, are buttons.

Of course for the price, going for simple capacitive touch pads, or cheap rubber dome buttons would be the best. But we do want to have at least a modicum of tactile feedback and comfort. So tact switches it is. I looked through what is available from the usual Chinese sellers, and mocked up a couple of layouts:

../../../_images/591831555539625614.png

You never before noticed how huge those buttons are, did you? Well, turns out the smallest you can get are about the size of a 1206 SMD resistor. I used similar buttons in the nGame before ( https://hackaday.io/project/27629-game/log/87435-ngame-revisited ) but they were horrible — designed as reset buttons for development boards, they require a lot of force to be pushed. This time I decided to try something more similar to the C&K PTS815 switches — they have a bigger cap and hopefully require less force. We will see. They do have 4 pins, though, which is a bit of an annoyance.

But this would be too easy. I also want compatibility with PewPew Standalone boards in terms of the connector for the extra pins. That is 12 pins with 2.54mm pitch, so a bit difficult to fit, especially since the top edge is going to be taken up by the flex ribbon of the display. So I came up with something like this:

../../../_images/1376611555541121625.png

It’s a bit bigger than initially anticipated, with some margins around the display — that should make it a little bit easier to fit everything. And it has the connector, and some free PCB real estate on the opposing margin, which can be useful for actually getting that thing mounted in a case, if it comes to that.

I’m sure the design will still change — I might decide to not put components under the display, for example — but this is at least some starting point.