According to the schematic document of picocalc, the two DIP switches on the motherboard are used to control two WAS7227s to achieve the “switching function” of the signal pins.
Moreover, we are well aware that the USB-C interface on the motherboard actually connects to a USB-to-UART chip (CH340C) by default, thereby enabling the purpose of serial communication with the Pico by connecting to the USB interface on the motherboard.
DIP 1 is used to switch between communicating with the Pico or the STM32. (This is quite understandable. When the firmware of the STM32 needs to be flashed, it is achieved by switching the UART to STM32, right?)
Here comes the confusing part:
DIP 2 is used to determine whether the data pins D+ and D- of the motherboard’s USB interface are connected to the CH340C or direct to STM32.
And this pin is also led out from the expansion interface on the side of the body.
Question
- So, in fact, I can directly connect to the STM32 via USB-C（With DIP 2）?
- Then why is there still a design of a USB-C → UART → STM32 link?
- Since we got DIP 2 ，What is the side expansion pins D+ D- use for?
