I'm trying to get 80 Gridseeds working across 4 Raspberry Pi's (24 Gridseeds for each Raspberry Pi using Monoprice 24-port USB hubs). However, I'm running into an issue with btbartle's cgminer:
http://i.imgur.com/wbdUUuA.pngIt looks like the Gridseeds are hashing, but only 3 of them have submitted shares, and a very low amount at that (and strangely, it always increments by a power of 2). Does anybody have any idea why this is happening? I've tried using the default 600 MHz speed and also using cpuminer, but the results are always the same.
I've finally figured out the source of the problem. It was the power adapters! I purchased 4 of the 20-Gridseed bundles, so I received 10 power adapters (each one can power 8 Gridseeds). After pulling my hair out for weeks, I finally narrowed the problem down to the power adapters. Only 2 of the 10 I received were working properly when powering multiple Gridseeds. When I cracked them open, it became really obvious as to why:
http://i.imgur.com/TKh1lyr.jpghttp://i.imgur.com/LfOVqlI.jpgLook at those capacitors bulging! All 10 of them had bulging capacitors. The capacitors in the 2 power adapters that were working had the least amount of bulge, but they were bulging as well. The worst ones were even leaking, and one even had a capacitor that was loose and barely connected!
If you're using one of these power adapters and are having issues where your Gridseed miners look like they're hashing, but are not submitting shares after a few hours, you can run this simple test to see if the power adapter is at fault:
Plug the barrel connector of the power adapter directly into a Gridseed and listen to the fan noise. It should be a fairly audible whir. Next, plug the 8-to-1 barrel splitter into the power adapter, then plug one of the barrel connectors on the splitter into the Gridseed. Listen to the fan noise again. If it sounds the same, your power adapter is working properly. If it sounds like it's spinning slower, then you have a bad power adapter.
I've since switched all my Gridseeds to use an ATX power supply and now they're happily hashing away.
