[time-nuts] Low cost logic analyzer
didier at cox.net
Fri Apr 25 12:45:27 EDT 2008
If it stops after a while you have it made. Set the trigger to normal and the scope will record the last transaction...
Well, I am sure it is more complicated than that, but my toughest I2C problem was a serial EEPROM that I was polling (for read) continuously several times per second. That device would have ONE memory location (always the same) corrupted every 3 months or thereabout of continuous operation.
It turned out to be a non-initialized variable in the i2c driver in my code that once in a great while would recycle to a particular value that caused the read to become a write...
I have an I2C analyzer that was useful to confirm the problem, but it was not helpful in identifying the problem. It is nicely made and not very expensive. It has a USB port so you can dump the data to a PC for off-line analysis.
Shortly after finding and fixing the problem, we decided to run Lint over the code. Lint would have spotted the uninitialized variable problem immediately, it did find a couple of other places where problems were just lurking...
---- Ulrich Bangert <df6jb at ulrich-bangert.de> wrote:
> I know some of you are hardware hackers like me too. In the 25 years of
> electronic development I have always refused to work with logic
> analysers and always have claimed "Give me a fast scope and some hours
> and I will do the job". However, these days I had VERY strange problems
> with an I2C bus based device.
> Communication on the bus would work flawlessly over hours and then stop
> due to... yes, due to what? That clearly is an situation where the "fast
> scope" mentality not applies. On the search for something affordable I
> came over this:
> I still have the device not here and still do not know the reason of my
> problems but the technicians at Intronix said to me "That is exactly
> what we have built it for" when I asked them very specific if their
> device could be helpful in this situation. It it were true this thing
> were worth its price in gold.
> Best regards
> Ulrich Bangert
> Ortholzer Weg 1
> 27243 Gross Ippener
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