I'm using an 18F4550 which has an internal USB module . I am also using its internal pullup resistors and the internal Vusb to drive them. I configured it for 48 MHz. (Everything I've tried to make the USB module work has failed).
I found something opposite to the data sheet concerning the USB D+ (pin 24, RC5) and D- (pin 23, RC4) and was wondering if anyone else has a similar problem.
The data sheet says
"UPUEN: USB On-Chip Pull-up Enable bit.
1 = On-chip pull-up enabled (pull-up on D+ with FSEN = 1 or D- with FSEN = 0)"
I'm using an 18F4550 which has an internal USB module . I am also using its internal pullup resistors and the internal Vusb to drive them. I configured it for 48 MHz. (Everything I've tried to make the USB module work has failed).
I found something opposite to the data sheet concerning the USB D+ (pin 24, RC5) and D- (pin 23, RC4) and was wondering if anyone else has a similar problem.
The data sheet says
"UPUEN: USB On-Chip Pull-up Enable bit.
1 = On-chip pull-up enabled (pull-up on D+ with FSEN = 1 or D- with FSEN = 0)"
"FSEN: Full-Speed Enable bit(2) .
1 = Full-speed device: controls transceiver edge rates; requires input clock at 48 MHz"
Since I want full speed, I set UPUEN to 1 and FSEN to 1. This should put 3.3 volts on the D+ line through Vusb to the internal pull-up resistor.
When I connect an o'scope to the D+ and D- lines it shows the opposite, i.e. D+ is LOW and D- is HIGH.
I have two questions:
Yes, it does work. If Hugh cam share what we have as am example this will show you how we have it working. I cannot post as I am traveling.