AVR-Chat

Thanks to all that have responded.

Shortly after I sent the email I thought about the possibility of a pin
seeing a negative voltage.  Anybody know what the effect, if any, would
be on the processor?  How tolerant is the ATmega16 of this condition?

I'd gladly submit the code to the group, but it's not available.  My
client wanted me to debug the existing product (with the EEPROM write
problems), but the original author has a contractual noose around the
code and won't/can't let loose of it.  I told my client I'd be wasting
his money trying to debug something without being able to review the
code and insert debug statements.  They've decrease the erroneous EEPROM
writes by making some code changes, but I've not been involved in that.
 The weird part about this problem is that it affects EEPROM locations
that are never written to after the initial set up.  They're suspicious
that somehow the address lines are getting modified (see previous
paragraph).

With this new product, my client will own the code.  It's in the early
stages - hardware has been designed (not by me) but I haven't written
any code yet.  Officially the project hasn't gotten the green light.
I've requested some minor hardware changes which will allow very early
brownout detection (independent of the internal BOD) ... details in
original message.

Thanks again for everyone's ideas.

James Hatley wrote:
> Hello Gary,
> 
> Well ... an interesting problem ... my opinions follow ...
> 
> If it was me the first thing would be to find the source of the EEPROM write
> errors in the similar application.
> 
> Check the read/write code ... check the grounds ... the bypassing ... the
> filtering ... etc. Find the problem.
> 
> Leave no stone unturned so to speak.
> 
> All else before finding the problem is by your own words presumption.
> 
> Find the problem first then evaluation fixes if necessary.
> 
> Jim
> 
> 
> 
> ----- Original Message -----
> From: "Gary J. Melvin" <n9auw@garmeltech.com>
> To: <AVR-Chat@yahoogroups.com>
> Sent: Thursday, April 06, 2006 8:39 AM
> Subject: [AVR-Chat] EEPROM writing with elec. noise
> 
> 
>> Hello,
>>
>> "Long time listener, first time caller."
>>
>> I've taken on an ATmega16-based project.  One of the requirements is
>> that I need to write up to 3 bytes of data to EEPROM in a potentially
>> electrically noisy environment.  I've never used its EEPROM before, but
>> it looks relatively uncomplicated.
>>
>> My client has another product in a similar application which has been
>> causing them a lot of grief with random EEPROM write errors, presumably
>> due to noise glitches.  (They use the built-in Brown Out feature  -
>> both trigger settings produced the same results.)  Obviously, this needs
>> to be solved with this new product.
>>
>> Here's the approach I suggested to them - feel free to shoot it down.
>> I've asked them to add a voltage divider before the regulator.  Run it
>> through a Schmitt Trigger to an input pin on the '16.  I've also asked
>> that they beef up the regulated voltage filtering to ensure at least 50
>> mSec of adequate power to carry it through a total drop out of the
>> supply.  (8.3 mSec, minimum, per EEPROM erase/write cycle times 3 bytes
>> of data = 25 mSec ... then double it for peace of mind.)  Before writing
>> the 1, 2, or 3 bytes of data, I'll check the status of the pin - if low,
>> I won't do the write(s).
>>
>> I'm open to suggestions.  If you have a better approach or a
>> bullet-proof algorithm, please enlighten me.
>>
>> Thanks!
>>
>> Gary.
>>
>>
>>
>>
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>>
> 
> 
> 
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