Hello, I'm new to electronics and programming. I have a lifetime of experience with computers but in completely different directions. Because I am retired due to illness and I have a lot of free time, I decided not to sit around for nothing. So, having a Rasperry Py 4 model B and a Pi Pico at hand, I thought of making a microcurrent generator, where the squares are as small as possible (in terms of dimensions).
**First challenge:** Raspberry Pi 4 or Pico? I would lean towards the Pico first of all because it is small but extremely versatile. What do you think?
**Challenge two:** What pin should I use? 3.3 V or 5 Volts?
**Challenge three:** I use a DACmcp4725 to convert the digital current into analog. I hope I'm not wrong. The problem is that I want to obtain a maximum current of 30V that I can adjust to whatever value I want using a GUI. So I have to control this module from the code on a user interface. I forgot to say that I would like this generator to have a touch screen.
**Challenge four:** If we have already arrived here, it means that we managed to have a maximum current of 30V. Good, now this current must be adjustable between 1-600 microamps. How do I do this? Respecting rule number three: monitor-code-GUI. Is there anyone who knows? Thanks in advance for the answers.

 

You might get some ideas from this project:
https://forum.allaboutcircuits.com/threads/micro-current-electrical-stimulation-device.126578/
It uses a timer and counter instead of a micro to produce the waveform, but downstream of that is a circuit for controlling current in your range of interest, less than 1mA. It uses a 9V as a power supply but could be adapted, I think, to use 30V for driving the current.

What is the purpose of the device you want to build?