18F4550 Not Recognised

[Squibcakes]

Dear All,

I've done some experimenting and found that USBSERVICE must be called at least every 2msec or lower. (10msec is way too long!)

The best way to do this is as Rob suggested, using DT's (Timer0 or1) interrupts.

The above example Rob posted is fine (every 100usecs) but may cause additional overhead for your program. Note, he's using an OSC speed of 48Mhz (PLL) to calculate TMR0H:TMR0L values.

Cheers
Squib

[Rob]

I've done some experimenting and found that USBSERVICE must be called at least every 2msec or lower. (10msec is way too long!)

Is that 2ms just for enumerating the device? After I get the device enumerated correctly I've been able to communicate over USB reliably with 10ms services; it's just too long for the enumeration process (in my particular program).

Note, he's using an OSC speed of 48Mhz (PLL) to calculate TMR0H:TMR0L values.

Yeah that's right! Should have said that really.

Cheers

Rob

[Rob]

Hmmmmmm - Squib I think you may be right about your 2ms or less USB Services.

Although I was managing to get my device to communicate reliably after enumeration with longer time periods between the USB Services, I did encounter a problem:

When the PC is turned off, there is still power on the USB which means that my USB device thinks it has just been plugged in. It therefore actions the quicker (100us) USBService for a short time. If the PC is then switched on, the USB device will not be found by my software as it has started issuing the USBService every 10ms. However, if I completely do away with the 100us USBService period and just replace with 2ms as you suggested, the device is found every time.

Thanks for that Squib, you've saved my head from getting sore, either by lots of scratching and/or head to desk contact!!!!

Rob

EDIT: After doing some experimenting I found that 2.1ms works fine, 2.2ms does not, therefore I'm going with Squib's suggestion of 2ms giving a bit of leeway (5%) - Thanks again!

[mister_e]

Hi Rob,
did you also tried without timer interrupts? have a look at Darrel's suggestion AKA POST 148
http://www.picbasic.co.uk/forum/show...&postcount=148

This use USB INT instead of a timer interrupt... really cool stuff!

[Rob]

Hi Steve,

damn it - why can't I ever find things like that when I search the forum - that's EXACTLY what I was looking for to see when the device was configured correctly. Thanks VERY much for that link.

Regards

Rob