A custom PCB is a nice feature to move from the protoboard to reliable connections.

My goal is to make a nice small and space saving PCB. Thus, I will not just plug breakout boards to their headers on the PCB but will solder them directly to the PCB.

With one exeption: The RP2040. I don't want to face any trouble doing the connections on my PCB - Controller - Crystal - Flash. I would like to take an off the shelf part - like the Pi Pico. But as already meantioned it is to large for my application.

My research led me to the RP2050 Femto which is a pretty nice approach to shrink the size. With a form factor of only 11x11mm it is just bearly bigger than the Controller itself. But unfortunately I coundn't find it to buy.

I heard also of the RP2040 stamp which is also a very nice board because it contains some extra features the Pico doesn't have. But 25x25mm is an unlikely formfactor for my project.

Next, coincidental I came across the RP2040 Nano which has a formfactor that suits my needs! Yes, not all pins are easy accessible but I don't need all the pins. It contains also some extra features like an reset button, a Neopixel LED and is future proof with a USB-C connector.

That's the board I take!

Next the PCB design wich is quite easy. I added another user button and two user LEDs.
To make use of the (so far) unused pins I added two rows of female headers. Their distance is in multiple of 2.54mm to easy stack-up another PCB.

The INA219 chip is addressable with all 16 addresses. One just need to change the position of the pull-up resistor.
In default assembly only one 2512 sized 100mOhm shunt is populated, but with higher currents in mind I added a second unpopulated footprint in parallel.

The screw terminal is the biggest component but also very robust and can hold wires up to 2.5mm².

Everything important is labeled in the silkscreen.

The PCB has a size of 75x30mm.

All files will be available on my github when everything is confirmed.

Now I might need a 3D printable housing...