Wrong description

[hetii]

Hello :)
I want to ask about pin PA1, what is the purpose to set it low?
Also in main() we can read that "Setup PB9 to pull up the D+ high." and then this bit is clear, so by what this pull-up is made?

[dword1511]

PB9 is connected to an inverter consisting of 2 transistors on Maple Mini. This is an odd design which is unnecessary in most cases. Pulling PA1 down is not mandatory. In fact, it may not have much effect at all. Just hoping grounding the pin adjacent to the input would reduce noise a little bit.