Problem with Inchworm ICD

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After researching this problem little bit, I am starting thinking that the 33pF may load certain types of crystals too much.

Still need a workaround for people who may have or will run into this problem with Inchworm units already shipped so I can post it on the website.

I do not currently have "bad" crystals, but can someone who had this problem try to run Inchworm with original non-working crystal and try to remove the 33pF capacitors entirely or replace them with 15pF?

The first person reporting successfully tested workaround (of previously dysfunctional unit due to crystal) that can be aplied even by the beginner will get free Inchworm from me for his efforts.
 

Will the free Inchworm come with a good crystal? Just kidding, nice to see you try and get to the root of this problem and sharing your findings. I'm sure we can all learn from the experiance and sharing experiances is what it's all about........

Lefty
 
I have 15pF caps here and a working Inchworm. If someone will send me a 'bad' crystal, I'll give you an answer for free.
 
toodles said:
I have 15pF caps here and a working Inchworm. If someone will send me a 'bad' crystal, I'll give you an answer for free.

I also have capacitors and working Inchworm, but not a non-oscillating crystal.

Leftyretro said:
Will the free Inchworm come with a good crystal? Just kidding, ...

After successful workaround to make bad crystals oscillate they will no longer be bad. The answer is ... the free Inchworm will of course come with good crystal
 
***Update***

I changed the 33pf to 15pf and the original crystal works perfectly. That work around did the trick.

Thanks again to everyone for all your help.

Jim
 
The future schematics and both the Inchworm+ & Unicorn kits will start shipping with 15pf. I've never had trouble with 33pf but the datasheet for the 18F4550 says 15pf and that's good enough for me.
 
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jeg223 said:
I changed the 33pf to 15pf and the original crystal works perfectly. That work around did the trick.

Thanks again to everyone for all your help.

Jim

As promised, Jim gets free Inchworm. Bill from Blueroom also gave me some PCBs to give away, so Jim will also get free Firefly, Inchworm+ and Unicorn PCBs.

Since we have a workaround now, I discontinued the recall for "bad" crystals, they just needed lower loading capacitors. I will add an extra set of 15pF to each Inchworm from the last batch.

Thanks everyone and mainly Jim for resolving this problem.
 
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