USB on 18F2455 funky problem

**Mark J** · - 23rd February 2011, 22:55

Hi guys,

Ive got a bit of a strange problem that I cant seem to fathom out.

Ive got an 18F2455 using the USB and on the breadboard it works fine, plug in a USB to the project and I can read and write the settings etc. but earlier today, I transferred the project onto an etched PCB (checked the PCB for any shorts etc all checked out fine) now here's the problem, it all works as it should BUT whenever I hook it upto the USB windowz comes up with the error saying something like 'theres a problem with the USB divice (sorry cant remember exactly but you'll probably know lol!)

I tried rewiring the USB port, changing the wire I used, even tried ultra short wires and nothing!
I tested the lines with my meter, and sticking one probe onto each pin individually on the USB port and the other on the actual pins of the pic chip and theres no breaks on either track so im at a complete loss!! (GND obviously to the GND line and shows continuity)

Im not using the 5V from the USB, as im using 24v PSU split down to 5V for the logic side etc, but I am obviously using the GND so that the PC and the project are grounded, and the D- D+ are correctly connected too.

So does anyone have any suggestions? I can add a schematic if needed, but everything else is working fine.

Many thanks,

Mark

**Darrel Taylor** · - 23rd February 2011, 23:07

Do you have a capacitor on VUSB? 0.22uF or greater?
And is the regulator turned on in the configs?

**Mark J** · - 23rd February 2011, 23:15

Hi Darrel,

Yeah ive got a cap on the VUSB, same on both the breadboard and the project.
regulator? youve got me there!

Here is my config settings from my project, and I think it was from a thread about USB that I think maybe you had written (but dont quote me on that lol!)
It all works fine when its sat on the breadbaord, just not when its on my PCB.

Code:

'****************************************************************
' Config settings
'****************************************************************

asm
__CONFIG    _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L  
                        ;              ;                      ; USB clock source comes from the 96 MHz PLL divided by 2
                        ;              ; [OSC1/OSC2 Src: /1][96 MHz PLL Src: /2]
                        ; No prescale (4 MHz oscillator input drives PLL directly)


__CONFIG    _CONFIG1H, _FOSC_XTPLL_XT_1H & _FCMEM_OFF_1H & _IESO_OFF_1H 
                        ;                  ;               ; Oscillator Switchover mode disabled
                        ;                  ; Fail-Safe Clock Monitor disabled
                        ; XT oscillator, PLL enabled, XT used by USB
                        
__CONFIG    _CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L  & _BORV_2_2L  & _VREGEN_ON_2L   
__CONFIG    _CONFIG2H, _WDT_OFF_2H 
__CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H & _CCP2MX_ON_3H 
__CONFIG    _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L 
endasm
DEFINE OSC 48
clear

Hope that helps.

**Darrel Taylor** · - 23rd February 2011, 23:26

The _VREGEN_ON_2L turns on the regulator, so you're ok there.

Does your PCB have a 4mhz crystal? That's what the configs are set for.

Are you running USBSERVICE often enough? ~1-2mS.

**Mark J** · - 23rd February 2011, 23:31

yeah im using a 4mhz xtal as theyre what I had handy at the time lol.
Im using your USB ints for controlling the USB and its set to 10ms interval on both the USB_POLLIN and USB_POLLOUT

Edit: USB interupts are running on TMR1