[SOLVED] My PC does not recognize a USB board based on PIC18F4550

[joseMiguel]

Hello,

One of my student realised a board based on PIC 18F4550. So, we succeed to connect to the board with ICD3 debug tools, we succeeded to use many features of the PIC 18F4550. But when we want to connect to the PC through USB, the PC does not recognise the board as a HID peripheral.

I succeeded to use the PICDEM FS USB and to make a small MMI to communicate with the PICDEM FS USB through the PC.

I verified the USB B connector.
The crystal is 20MHz and the clock is divided by 5.

If you can give sone idea to investigate, you are welcome
Thank you in advance.:grin:
(sorry for my english)
Jose Michel

 

[horace1]

does the PC do anything ? e.g. does nothing or says it does not recognise the board?
a few of the things we have found when getting USB working
1. check the config settings to make sure the prescalers and postscalers etc are correct, e.g. can the board talk to a UART OK
2. look at the D+ and D- lines with an oscilloscope - do the signal level look correct
3. is VBUS connected ?

 

[FvM]

If the USB interface hardware is enabled in the processor, the PC would at least detect an unknown device, that also shows up in the system manager.

 

[joseMiguel]

hello,
The board is still not recognize by the PC.
The UART is working (FOSC=48MHz; GRGH=1; BRG16=0; SPBRG= 155)
I tried to power the board with VBUS and also with external power supply.
No results.
Best regards
JoseMiguel

 

[joseMiguel]

Hello,
Right now, the PC see the small USB board as a HID device, but winXP indicates a problem.
the vid and pid are 0x4D8 and 0x3F.
Could you help me please.
regards
Jose Michel

---------- Post added at 18:59 ---------- Previous post was at 18:57 ----------

Hello, again,
for these reasons, the small MMI(PC) does not work.
i can not connect to the usb board.
regards.
JoseMiguel

 

[joseMiguel]

hi,
i will try again tomorow with a "clean head" and another PC.
(it seems to be a classical problem, and perhaps i need to reload the driver???)
regards
joseMiguel

 

[FvM]

With other USB deviced classes than HID, there may be in fact a problem, that a different USB device driver is registered for the VID&PID combination. But I thought, it's not possible with HID that uses a generic Windows driver.

Is this recent report describing the present problem correctly?

Right now, the PC see the small USB board as a HID device, but winXP indicates a problem.
the vid and pid are 0x4D8 and 0x3F.

So, which problem is indicated by WinXP? Did you try to trace the communication with an USB software monitor? Are you sure the HID descriptors are correct?

 

[bigdogguru]

Hi Jose,

You mentioned your student "realized" this circuit, did he include a 470nf Cap inline with the VBUS as shown in the following schematic?

The capacitor is necessary for the USB section to function properly. Also if you could upload the code it would be helpful.

 

[joseMiguel]

Hi,
thank you for your answers.
so happy to find the issue, and the student more. There were a problem of ground on the VUSB capacitor.
How i can close the thread.
thank you again.
regards
JoseMiguel