PDIUSBD12 & PIC problem !

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glias

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Hi all !
I'm trying to develop a USB card with a PIC16F877 and a PDIUSBD12... and I have a problem with the USB controller. In fact the PDIUSBD12 don't seem to have the good level on its interrupt line. I configure the pic with the pull up resistor... and when I turn ON my board, the interrupt line always 0 !
Does anyone have an idea ? Is it the right initial level ?

Best regards,
Julien.
 

I have not worked with the Philip's chip before, but I once worked with it's National counterpart. Anyway, the interrupt is an active-low interrupt. If I'm not wrong, the interrupt signal will remain low as long as the interrupt conditions on the usb controller has not been cleared. However, the PIC's external interrupt pin is edge-triggered, so there may be a chance that usb events are happening so fast that multiple usb events trigger only one single interrupt. So if you serviced only one single event, the remaining events won't trigger any more interrupts, and the interrupt signal line will stay low!

Try doing a reset with the chip disconnected form the usb host. Is the interrupt pin signal level still low?

Hope this helps. Cheers!
 

Thanks a lot for your response... Well yes ! the PD12 interrupt signal line is still low when the USB chip is diconnected to the host !
so... I'm not sure that it is normal...

Best regards
Julien.
 

It's expected to be low when it's disconnected from the host as there are still unhandled USB events. But is it always low even after a power-on reset? Note that resetting the PIC does not imply that the usb controller gets automatically reset as well.
 

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