AtMega 162 EEPROM Corruption

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AndyG
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Posted by AndyG: Wed. Nov 9, 2005 - 11:19 AM
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Hi

I have a product based on an AtMega 162 that has a number of configuration tables held in the internal EEPROM. Specifically this is a stepper motor controller for a fruit machine (one-armed bandit) which can spin up to 8 reels.

As the reels spin, the MCU has to keep reading from EEPROM to determine the number of milliseconds until the next change of stepper motor phase.

A single byte of the EEPROM is getting corrupted occasionally over a power cycle. Curiously, this byte is the byte that determines the standard period between phase changes for normally spinning reels. That means it is a single byte of EEPROM that is being read up to 8 times during a 16 millisecond period.

I know that the most likely cause of this is a software error and that we softies are all too keen to want to blame the hardware, but I have checked the code very carefully and cannot see any practical circumstances in which I could write to the EEPROM at all under these conditions.

Does this potential corruption ring any bells out there?

Thanks in advance,
Andy G

If we are not supposed to eat animals, why are they made out of meat?

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AVR Microcontrollers, megaAVR and tinyAVR
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reynaert
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Posted by reynaert: Wed. Nov 9, 2005 - 11:53 AM
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I've read somewhere that location 0 in the EEPROM has a tendency to get corrupted on power cycles or glitches or something like that. Anyway, if you're afraid that repeated reading is the cause, why not keep that byte in SRAM, or in a register ?

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AndyG
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Posted by AndyG: Wed. Nov 9, 2005 - 12:12 PM
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Thanks, but I already knew about the location 0 problem and specifically ignore thast location.

Although you are right, I could keep THIS value in RAM, the problem is that I have tables held there and don't have enough RAM space to hold the tables. We do intend to re-spin the design to a bigger AVR, but that will take a little while.

My worry is that if this is a genuine hardware problem, then I will see the same effect with the other parts of the tables; it's just that this will happen less frequently.

Thanks for the suggestions, though.
A

If we are not supposed to eat animals, why are they made out of meat?

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theusch
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Posted by theusch: Wed. Nov 9, 2005 - 03:31 PM
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Is the brown-out detector enabled? If not, re-run the tests with internal or external brown-out detector.

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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sutton
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Posted by sutton: Wed. Nov 9, 2005 - 04:23 PM
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Try leaving the address reg for the eeprom at 0 after each operation.

Keep it simple it will not bite as hard

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AndyG
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Posted by AndyG: Sat. Nov 12, 2005 - 09:48 AM
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Thanks, I'll give that a try.

Sorry about the lighting response - I got distracted for a couple of days.

Andy

If we are not supposed to eat animals, why are they made out of meat?

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