View Full Version : crystal problems maybe

11-14-2010, 03:15 AM
Hi Guys,
I got a weird problem lately. I am building up and troubleshooting a new board with a prop. However, it's operating a bit flakey. For instance, I use the ftd chip that is used on the demo board for programing and communication and sometimes it programs other times not. I put a piece of software that sends a repeating string back to the terminal and it runs but stops eventually, and sometimes starts up again.

I'm really suspect the crystal. This is the first time I bought the crystal from digikey instead of parallax. Is there something special about this crystal?
Just wondering

11-14-2010, 11:09 PM
I've used about half a dozen different crystals with the Prop ranging from surface mount to through hole and they all worked without a hitch, so its doubtful that the xtal is the issue.

It would be helpful if you could provide some more information, what is the Digi-Key part number of the crystal, what crystal drive strength setting is being used in your code and is the PLL (PLL16X?) enabled?

Mike Green
11-14-2010, 11:21 PM
Strange things do happen sometimes, but it's a bad habit to attribute flaky behavior to passive components like a crystal. On a new design, it's much more likely to be a bad connection or noise partly from how signals are routed. Downloading programs to the Propeller doesn't use the crystal, so occasionally not being able to download a program points to something else.

11-15-2010, 06:51 AM
Well, apparently the problem I had was water or water soluble flux living under some of my chips. Even after heating and drying out the boards for sometime the water soluble flux just messes things up. I ended up blowing the moisture out and fixed that particular problem.
Thanks for the help anyway guys.

11-15-2010, 09:33 PM
Well, apparently the problem I had was water or water soluble flux living under some of my chips.

We (EFX-TEK) have run into that a couple times and are now having the crystal soldered in after the board is washed.