Possible issue with some PIC18F2550 samples and a fix.

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Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Sun Jul 20, 2008 10:34 pm

I had a strange issue with one of two PIC18F2550 chips today. USB was working fine with one of the chips but not with another.
The only way to make this chip work was to pull pin 26 of PIC18F2550 to +5 over a 10k-47k resistor. Weird.
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Fri Dec 12, 2008 7:34 pm

If you happen to encounter a similar issue try this firmware:
pic18f2550usb_midi.hex


pin 26 should be connected over a 22k-47k resistor to ground instead.
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby Xmattz » Sat Dec 13, 2008 4:37 pm

Dimitri, stop talking in russian in english section of forum... ;)
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Sun Dec 14, 2008 6:14 pm

This is the source:
PIC18F2550 USB.zip
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Fri Feb 13, 2009 7:59 pm

By now several people have had the same problem I had and all of them confirmed that this PIC18F2550 USB MIDI firmware fixes it, of course, with the required small schematic change (pin 26 should be connected over a 22k-47k resistor to the ground).
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby r0bbie » Sat Feb 14, 2009 12:04 pm

Hi Dmitri,

Finished my hardware (Synthex) yesterday, and gues what, USB problems.
I found this post this morning and added a 33k pulldown resistor to pin 26.
Problem solved, without updating firmware. should i worry?

Thanks
If it ain't broken try to improve it.
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Sat Feb 14, 2009 12:12 pm

If it works - it usually works. Just do a bit longer testing.
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby NovaKaine » Tue Feb 17, 2009 6:39 pm

Grrrrrr :lol:
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby dmitri » Sun Mar 15, 2009 10:38 pm

This file contains 5 PIC18F2550 USB MIDI firmware versions for 4/8/12/16/20MHz crystals:
PIC18F2550 USB_4_8_12_16_20MHz.zip


In theory, by using the same frequency firmware for both Atmega and PIC18F2550 it may be possible to use just one crystal instead of two.
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Re: Possible issue with some PIC18F2550 samples and a fix.

Postby Ken Forgettable » Sun Mar 15, 2009 11:16 pm

dmitri wrote:This file contains 5 PIC18F2550 USB MIDI firmware versions for 4/8/12/16/20MHz crystals:

XMEGA dev' :ugeek: - just with a change to CLOCK_FREQ in "HardwareProfile - pic18f2550.h" for these then?
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