Unit variation Omega2S+
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Hi,
We have built a number of boards with the Omega2S+ installed, we are experiencing "oddness" with some units.
The prototype that we have been using doesn't have any issues at all but some of the new boards we have built exhibit flash failures when they get warm (not hot).
If you leave them off for a while they work fine for a while. We were using a build with 80MHz SPI max speed which appeared to work fine on our original unit for about 5 months of being turned on and working. We are trialling back at the stock 40MHz to see if this makes any difference.
Anyone else seen any temperature dependant issues?
Thanks.
Liam.
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@liamski are you sure it is the Omega2s+ and not another component causing your issue? I have some sitting in waterproof boxes on rooftops and on top of 30ft poles. They are subjected to temperatures from 2 degrees C to 40+ degrees C and I haven't had any issues. I had to change the zip tied because they were melting when strapped to steel poles or perishing due to the harsh UV conditions. I also had a magpie attack one of my boxes and send it plummeting to the ground. I think it was mating season and the box was hot
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@crispyoz, thanks for the info. I can't see what else would be causing flash/SPI failures. It's not evident until you actually read/write the flash of course and goes away when they cool down. So unless your application writes to the flash you wouldn't see it necessarily. I mainly see it when booting up, during development process.
I think it is a combination of things, running at 80MHz and temperature. I have reduced the speed on the failing units and this does clear the issue I think, on test now. Haven't seen it all day so far.
It's just odd I had one running at 80MHz in a really hot office for about 5 months and had no issues with it. The other modules from the same batch all exhibit the same issue at the higher speed. Pure luck that the module I selected for the prototype was "a good one".
Shame they can't run the SPI faster though. I believe the flash chip is capable of running over 100Mhz.
Thanks.
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@liamski I can't answer for the technical reason, only my experiences with high temperatures and Omega2S+ (and Pro). However a few decades ago when we were building custom PCs for some high traffic security software we would regularly overclocking CPUs. A pattern quite clearly developed that the maximum clock speed varied quite significantly between batches of SIMM modules. In fact OS/2 (if anyone remembers that) was quite unreliable if you used SIMM modules from different batches. So your experience is not that surprising to me.
I think it has something to do with gravity or sun spots or maybe a combination of the two.
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@liamski Hi, if your prototype used the Omega2S+ or Omega2+ Module? And is there any circuit change around the Omega2S+?
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Hi, @JeffZhou, all boards use the Omega2S+version. The prototype is almost the same, just a couple of unrelated circuit changes. It does look like the problem goes away running the flash at 40MHz (max) in the DTS. I was trying to push the limits so I think it's down to silicon variation, some are happy at that speed/temperature some aren't. Thanks.
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@JeffZhou, it's worth noting that the stock OpenWrt DTS available from Onion does have it set to 40MHz , probably for this exact reason, so it's not a problem for normal builds from the Onion repository. Only when you start to push the boundaries does the issue become apparent. The flash chip itself is rated to 120MHz (I think) so you'll forgive my temptation to try and run it harder rather than settle for 1/3rd of the rated speed
