Happy New Year one and all!
Here at Spell Foundry we’re looking forward to 2014 and all that it holds. It has been far too long since my last post and my New Year’s resolution has got to be to post more content and more often!
So what’s been happening in the dungeons (ok, workshops – we don’t have a dungeon…yet) of Spell Foundry? As usual far too much and that’s my excuse for not publishing more 😉
Sleepy Pi: We opened up for pre-orders just before Christmas whilst waiting for the first batch of production boards to arrive. The hope was to ship the first boards before Christmas, but on testing the first sample batch of boards, I noticed a curious issue. All of the boards were working, but on some of them, the DC-DC converter was not entering “Power-Save” mode at low enough input voltages – they were fine at higher voltages.
To give a bit of background, at light loads i.e. when everything is asleep, the DC-DC converter will enter a low power maintenance mode. The Sleepy Pi can work off input voltages between 5.5V and 17V (it will actually operate below 5.5V – but you probably wouldn’t want to make a habit of it ). Anything over around 6V and with the RasPi powered off, the DC-DC will enter “Power-save” mode – except on some of these initial boards this would be in excess of 8V. As we’re trying to save all the power we can here, on these boards the DC-DC would be in “active” mode and consume it’s “awake” power below 8V which wouldn’t give us our best power saving.
To cut a long story short, lots of measurement action and comparing “good” boards with “bad” boards, a simple Inductor alternative seems to have cured the variability and brought all the boards into the area of optimum power-saving. Hurrah!
I’ve got a few more tests to do and with a larger sample of boards, but at this time the signs are good and I hope that first boards will ship very soon…