Hi Folks. I'm having some trouble getting an FT312 design working on a custom board, and I'm looking for some help debugging my problem. I connected my board to a phone with the FTDI app and tried to send a character, resulting in an error message that tells me that I need to connect a cable. The app worked on the same phone with FTDI's FT311 dev board. I've attached a snippet of the relevant parts of my schematic.

Power

The 3.3V power to the FT312 chip looks good, and it is producing a 1.8V AVCC voltage from the internal regulator.

The Oscillator

I can confirm that the 12 MHz oscillator is oscillating (checked with a scope). I know that parasitic capacitance from the scope probe can cause the oscillator to either start oscillating if it wasn't already or stop oscillating if it was working in the first place. In any case, the phone doesn't recognize my board with or without the scope probe connected to the oscillator.

Log Files on the Phone

I have inspected the phone's log file using adb. I'm seeing the following lines that appear to be in response to plugging my board in to the phone:

12-16 06:38:55.450  1438  8651 I UsbPortManager: ClientCallback V1_1: port0
12-16 06:38:55.451  1438  1498 I UsbPortManager: USB port changed: port=UsbPort{id=port0, supportedModes=dualsupportedContaminantProtectionModes=0supportsEnableContaminantPresenceProtection=falsesupportsEnableContaminantPresenceDetection=false, status=UsbPortStatus{connected=false, currentMode=none, currentPowerRole=no-power, currentDataRole=no-data, supportedRoleCombinations=[no-power:no-data], contaminantDetectionStatus=0, contaminantProtectionStatus=0}, canChangeMode=true, canChangePowerRole=false, canChangeDataRole=false, connectedAtMillis=0, lastConnectDurationMillis=2024939


I'm not really sure what to make of this. I also tried using lsusb to inspect what usb devices are connected (on a different phone that is rooted), and it reports nothing connected. I'm not sure if I should expect lsusb to report my board or not since the phone should be acting as a USB host (not a device).

Some input on this would be greatly appreciated because I'm totally stuck. Thanks.