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7555 Clock Issue in Lesson 6 and 7

Posted: Wed Dec 31, 2014 1:07 am
by ricochet82
Hi. I bought the CPLD kit and have been working thru the tutorials. It has been a great experience.

I am having problems with the 7555 clock being detected or maybe processed by the CPLD. I have a scope on the clock output and can see it generates consistent clocking, but the output pins are missing counts (e.g. they literally are skipped). For example, in lesson 7 which is currently setup, the LED will cycle thru something like 1,2,3,5,6,7,9 (and this is not consistent).

I discovered if I feed the clock from a function generator, no problem. The only difference I see is the function generator provides 3.6v and the 7555 is providing 3.28v.

I created a separate 7555 running on 5V and fed it's clock to the CPLD. That works 100% correct. I then used a fixed 3.3v power supply that produces about 3.4v and it works nearly correctly on that - dropping only the 0.

You don't have any problem on your videos. I've checked the code and wiring repeatedly and see no problems there.

I'm baffled.

Dan

Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Wed Jan 21, 2015 2:09 am
by ThePyroElectro
ricochet82 wrote:Hi. I bought the CPLD kit and have been working thru the tutorials. It has been a great experience.

I am having problems with the 7555 clock being detected or maybe processed by the CPLD. I have a scope on the clock output and can see it generates consistent clocking, but the output pins are missing counts (e.g. they literally are skipped). For example, in lesson 7 which is currently setup, the LED will cycle thru something like 1,2,3,5,6,7,9 (and this is not consistent).

I discovered if I feed the clock from a function generator, no problem. The only difference I see is the function generator provides 3.6v and the 7555 is providing 3.28v.

I created a separate 7555 running on 5V and fed it's clock to the CPLD. That works 100% correct. I then used a fixed 3.3v power supply that produces about 3.4v and it works nearly correctly on that - dropping only the 0.

You don't have any problem on your videos. I've checked the code and wiring repeatedly and see no problems there.

I'm baffled.

Dan


I know we e-mailed back and forth a few times. I wonder if you ever figured out the issue here.

Seems to be a very, very odd bug.

Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Thu Jan 22, 2015 10:43 pm
by ricochet82
Never did figure it out. Every lesson required 5V on the clock pin to work. I used different CPLDs, 555 timers, power supplies, etc. Completely bizzare. But I've moved on to a MAX II with an onboard clock now.

Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Fri Feb 20, 2015 11:49 pm
by ThePyroElectro
ricochet82 wrote:Never did figure it out. Every lesson required 5V on the clock pin to work. I used different CPLDs, 555 timers, power supplies, etc. Completely bizzare. But I've moved on to a MAX II with an onboard clock now.


Sorry I couldn't give you a better answer. I used many different 7555 countless times as a clock both fast and slow and could never reproduce what you saw.

Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Mon Mar 16, 2015 11:01 am
by Ayan Prince
I wonder if you ever figured out the issue here.



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Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Mon Mar 16, 2015 3:11 pm
by ricochet82
I did not. I moved to an Altera MaxII and never experienced any problems with it.

Re: 7555 Clock Issue in Lesson 6 and 7

Posted: Tue Mar 31, 2015 1:52 am
by ThePyroElectro
ricochet82 wrote:I did not. I moved to an Altera MaxII and never experienced any problems with it.


Glad to hear it worked. Moving to newer technology might have helped as well :shock: