You might think that there is absolutely nothing challenging in simply connecting a screen and a bunch of buttons to a microcontroller development board, and you would be right. I have done it so many times by now, that it should be simple even for me. However, as the saying goes, the devil is in the details.

First of all, this is the first time I'm using the Raspberry Pi Pico development board, and it's not like other development boards out there. On one hand, it has a build-in buck-boost converter, which makes it nice to use with the batteries, on the other hand it doesn't have the power switching circuitry that disables battery when USB is connected — so there is an extra bit of electronics with a MOSFET needed to be added. I'm worried about this, because I have always had bad experiences with power circuits like that.

Next is the audio output. On my previous consoles, there simply was a DAC pin, where you connected the speaker or the amplifier and speaker, and you were done. Here the audio output is PWM-based, and I will need a low-pass filter to smooth it a bit before feeding to an amplifier. Plus, I want to have a volume control, but the only small sliding potentiometer I found is around 9kΩ, which is a bit low to just make it a simple voltage divider. Some experimenting will be needed, and again, analog circuits are scary.

Then there is the display backlight. It uses four internal LEDs, and I could do what I did previously, just connect them straight to the battery with a current-limiting resistor. But it would be nice to have backlight control, and even a light sensor, to adjust the backlight brightness to the environment. More scary transistors and analog circuits to worry about.

Finally, and that is going to actually take the most work, there is the question of design. Selecting the best (both in terms of functionality and price) components, and finding an arrangement of them that is both functional and aesthetically pleasing. Designing the shape of the device, its case and its controls. I have already done some work on this, much much more remains.