Hi Vsurducan,

The datasheet of the 18f14k50 states this:

"For full-speed USB operation, a 48 MHz clock is required for the USB Module. 
To generate the 48 MHz clock, only two oscillator modes are allowed:
-) EC High-Power mode
-) HS Mode"

I have seen a sample file that runs at 48 MHz but uses the internal oscillator, 
see 18f67j50_usb_serial.jal.

I am not sure if this answers your question.

Kind regards,

Rob



________________________________
Van: [email protected] <[email protected]> namens vsurducan 
<[email protected]>
Verzonden: donderdag 18 februari 2021 15:09
Aan: [email protected] <[email protected]>
Onderwerp: [jallib] USB issue

Hi, I've seen two complete examples of using USB libraries; both are 
bootloaders, one using 18F4450 and the other 18F14k50.
Both are using USB clocks at 48MHz, so USB runs in full speed mode. Both use an 
external crystal in HF mode and PLL to acquire 48MHz clock.
The bootloader for 18F4450 works ok also on 18F2550 without any issue...I've 
tested a while ago.

I'm trying to use usb_serial on a 18F25k50 running in INTOSC mode 48MHz (16Mhz 
and 3x PLL) and USB module in low speed mode (6MHz).  The computer does not 
read OK the USB device descriptor when the PIC is connected. This can be a 
communication issue but also a software error.

Anyone know if full speed is mandatory for these USB libraries?
Maybe there is another example of using USB which I missed?

thank you all,


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