Hello, i have designed a custom board which uses the Atmega328p procesor to connect to a nrf24l01 module, it is meant to be purely a proof of concept and is mostly useless on its own.
The objective of this board was to see if i could make a custom Arduino board and have it connect trough USB to the Arduino IDE + verify nrf24l01 design but that's beside the point.
The board uses the CH340G/C(i'll get to why both later) as the USB to Serial chip connected to a USB-C connector, i have chosen to use a 12MHZ resonator for the CH340G and a standard 16MHZ resonator for the Atmega328p.
Something to note is i noticed that on some of my Chinese Nanos they pulled the CC pins of the USB-C
Here is the Schematic
and here is the PCB
this is the current state (only the parts for the Nrf24l01 and the 5v regulator used for Non-USB power are missing)
After plugging it in there are a few things to note, first the Atmega328p chip is functional as evidenced by blinking on the D13 LED (i pre-burned code on it to show that on an Arduino Nano and then de-soldered it off the Nano to solder it on here).
Second, i measured the 3.3V pin on the CH340G and found out that it only had 1.77V however when i soldered on a CH340C from the Nano which i canibalised for the Atmega328p the voltage was now the proper 3.3V.
Third the voltages on the D+ and D- pins after the soldering of the CH340C were 2.5V on D+ (Occasionally dropping to ~1.7V for a split second every 1ish second, this was measured with a multimeter so it could be getting pulled down low and the multimeter didn't have time to react) and on the D- pin there was always 0V.
The final thing i have to mention is that both the TX and RX pins on the CH340C were pulled to 5V, from testing with de-soldered resistors i know that both the CH340C and the Atmega328p are pulling the pins to 5V.
From this i think we can gather that the problem is likely on the CH340C side however i am completely stumped as to where exactly it is.