A Little Bigger Please?

Published on 2019-07-18 in PewPew M4.

I have just spent a week at the Europython conference, with all participants being given PewPews to play with. We also ran two days of workshops for programming them, and I got to help a lot of people trying to program them in between the talks. So I have some thoughts.

First of all, the serial console is a weak point. People don’t know about it, don’t know how to access it, and as a result don’t get to see the exception messages. So then they just try to change things randomly or stare at their code looking for errors. We can’t count on serial support being built-in into the editor, as not everyone can install Mu or a plugin for their editor, and sometimes they simply are not in the dialup group and don’t have the admin rights to add themselves. The modemmanager thing on Ubuntu is also extremely annoying, as are the extra drivers needed for Windows 7 and 8. I really need a better way of displaying errors, so the screen is an important addition.

Second, colors. People love colors, and are very disappointed that they can’t change the color of the LED matrix from the code (one can’t help but wonder about their mental model of the underlying hardware, but let’s not get into that too much for now). Also, while kids don’t mind tiny screens, adults often do, even when there is nothing wrong with their eyesight. Not to mention the buttons, which were too small for some hands even in the large version of PewPew.

So I’m thinking that I really should use that 160x128 1.88” color TFT screen. It has colors, it can display the console or menu, and it’s still relatively cheap. It will never be as bright or visible from distance as the large 8x8 LED matrix, but that’s not the main use case. Of course, the problem is that pushing so many bits to the display each frame is not fast enough for smooth animation. So let’s also upgrade the microcontroller, and use the SAMD51 — sure, it’s more expensive, but it’s only \(2. I think we can still fit in the magic barrier of \)10 with that. And PCBs are getting cheap too recently, so let’s use a bigger PCB that is easier to hold.

So all in all, a more capable hardware with fewer hacks, for a little higher price, but much improved convenience. Of course I started mocking it as soon as I came back from the conference:

And since I couldn’t sleep a few nights afterwards, I designed a PCB as well:

As you can see, I’m using:

• PCB the size of a credit card,

• TFT screen,

• wider-spaced buttons,

• same connector, but now with better descriptions,

• same two AAA batteries,

• only the minimum necessary parts.

Once it arrives, I will need to experiment with bootloaders, linker scripts and so on to get CircuitPython to run on it, and then I will write a version of the Pew library that simply displays 8x8 huge color blocks on that screen. If it proves fast enough, maybe I will be even able to replace those blocks with custom GIF images later on? Who knows?