RP2040 Pro Mini

# Introduction:

It is pin-compatible with sparkfun's pro micro/mini and can be used with my USB2USB baseboard instead of the Pro mini core board.

* Simplify the circuit and simplify the power supply. The independent ADC reference voltage has been canceled (because it is basically not needed). It can only be powered from USB, and the external power supply can only input 3.3v (or 5v from vbus).
* Use mini usb interface, personally don't like type-c interface.
* There are USB interfaces on both front and back sides, which can be welded on the front or back.
* The 2.4g wireless serial port module pad is reserved on the back. But since there is no uart interface available, PIO simulation can only be used (if it is used). Because pio simulation is used, I2C SPI devices can also be accessed.
* SPI flash originally wanted to use SMD, but I was not sure whether it was in stock. I was worried that there would be no stock when making the board. Just use big, stupid traditional flash.

## For other instructions,

refer to the Raspberry Pi Pico official manual, and refer to the RP2040 chip manual.

Refer to the project for USB2USB backplane: USB2USB Pro Mini-3.3v.

Updates and corrections may be made after the board is made.

### Log

* 2022-02-05: After the board came back, the flash chip was soldered and tested, and it was available normally. (There is still a piece of soldering waste)

## Physical picture

### The first version of the physical picture

! [rp2040-mini-pic-01.jpg] Above picture: Comparing the pro mini core board
! [rp2040-mini-pic-04. jpg] Above: The effect of installing it on the bottom plate instead of pro mini. (The USB socket is installed on the back, and the flash uses a pinless package)