- Please let us know the PMODE[2:0] pin connections.
- When using USB boot, are there any unknown devices appearing on the device manager?
Have you solved this problem?
You could follow the below instructions to find the root casue.
1. USB boot should be a simple and quick way to boot since FX3 doesn't need load firwmare from external device. When it fail, you should check if the PMODE pins are correct value. If not, FX3 will not enumerate as expected.
2. When you solder an external EEPROM and switch to I2C boot, the PMODE pins may get correct value and it could boot as expected.
The questions is why the PMODE pins are incorrect in USB boot but correct in I2C boot. Maybe you do something wrong(maybe hardware design defect) here.