HELP

This forum is used for discussing hardware, software, and technical details of the AVRcam embedded system.

HELP

Postby UniStudent » Thu Oct 13, 2005 6:36 am

Please Help Me!!

I have a major assignment due in 4 days. I have been using the AVRcam on a device and taking image dumps and storing them onto RAM. It has been working fine for a couple of weeks, until today when the data stream started looking a little strange.

I realised that the 9V battery I was using was actually running at 6V so I changed it.


Then the yellow light would not light up. It won't boot up and I don't know why. I have checked the connections around the board. All seem in order. I don;t know what is happenning.

Help Me.

If there is anyone in Sydney Australia who has an AVRcam available, I am more than happy to pay full price for it if I can get it by Sunday.

Sincerely,
CB

cbru2253@mail.usyd.edu.au
UniStudent
 

Postby Guest » Thu Oct 13, 2005 8:36 am

I've responded privately over email...to follow-up with our email conversation:
-CB reported that the 17.7 MHz clock signal is appearing at pin 9 of the mega8, and thus the tiny12 is powering up properly, sending the I2C commands to the OV6620 to enable its external clock, and presumably releasing it from reset properly (actually, can you double check the level of the reset pin on the mega8 to make sure the chip isn't in reset? It should be logic-high (~5V or so).

-The yellow LED doesn't blink, which is one of the first things that happens in the system...do you have an AVR ISP programmer connected to the system? I think I vaguely remember that someone reported that if they had the AVR STK300-compatible programmer connect to the parallel port on their PC and hooked into the system, one of the i/o lines used for programming could be held in a funky state to prevent proper startup (the mega8 thought a programming session was being started, and thus didn't execute any code). So, if a programmer is connected, try removing it, which will force all the re-programming lines to normal states.

Any one else seen anything odd like this? I have certainly had a power supply dip to low, but it didn't cause any permanent damage to the system. Very strange indeed...
Guest
 

Postby Guest » Thu Oct 20, 2005 4:29 pm

Just to follow up...after going back and forth on email, we finally diagnosed the problem. Turns out there was a part on the AVRcam board that had been wiggled back and forth a bit (I believe it was the transistor that helps control the reset of the mega8) to the point of breaking. Anyway, the mega8 was never being brought out of reset due to the transistor being fatigued. Sounds like their quick-fix was to simply remove the reset pin from the socket so that it wasn't being constantly pulled low. As a side note, this basically means that the reset line is floating, and the system is more succeptible to noise (and randomly resetting). So beware if you ever try to do this to the system.

Chris: do I have this right? Do you have any more insight into the problem? Did you ever get the mega8/tiny12 I shipped you overnight???
Guest
 


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