We need 20 analog outputs with adjustable voltage (0-20 volts), frequency (0-150 Hz), as well as adjustable maximum current, and also the ability to measure current, frequency and voltage.
How can this be implemented using PI?
I know there is an analog zero module for Pi, but it will take up all the GPIO pins and give only 8 analog outputs. In addition, it is unclear whether he can do it all.
From my knowledge there is no ready to buy solution.
I would recommend to use a I2C bus with the required converters connected to it.
And in addition to above a lot of analog design.
The Pi is a great way to process data especially if the desired output is digital (Binary) in the physical form, it is however less able to handle analogue inputs and outputs.
To assist the Pi, HATs/processors can be connected via the SPI or I2C interfaces. When you do this for 20 off outputs you will find that costs increase and you start to leave the world of software and enter the world of electronics, instrumentation and control.
It may be more cost effective to use purpose built I/O to handle the physical outputs RS485 interface and the Pi to supervise the control. I would reccomend something like the Fuji Electric module https://www.coulton.com/fuji_module_type_controller_pum.html
