My PCB has a FT230XS-R USB to UART communicating with an AVR chip. My first prototype board worked perfectly except for the USB problem stated in post title. I triple checked everything. Can NOT find why I'm getting this error. This may be a design flaw on my side? I followed the "Self-Powered" configuration on page 23 in the datasheet exactly as displayed.
Things I have checked:
Solder bridging?: Everything is reflow soldered, I still checked under microscope, it's perfect.
Still used a MM to check for shorts: None.
Checked cable: Good
Power supply quality: < 2mV peak to peak
Correct USB connector pins go to correct inputs: Yes
I triple checked the pinout on the datasheet against my PCB: Everything's correct.
I checked ground, VCC, and VCCIO values. Everything's normal.
I remade a PCB, I left every component unpopulated except for the FTDI chip and peripheral components needed to run the chip. Still had the same problem.
I tried removing RX and TX LEDs: Nothing.
I then removed 47pF caps and 27 ohm resistors: Nothing.
I am at a loss. I contacted FTDI. They only said I have a short somewhere, and they asked for a schematic. I sent them the schematic, never heard back from them.
Could vias on my USB signal lines be corrupting the signal? Any info is greatly appreciated. I uploaded only relevant schematics and PCB design snapshot.
Please ignore U9 and pads directly above it, they are unpopulated. They were never populated for either test.
Thank you so much.