Peter Stuge wrote: > Michael Carbone wrote: >> I have been attempting to use a raspberry pi for spi flashing and when I >> use the 3.3v pin the raspberry pi doesn't power up as the chip draws too >> much power through the 3.3v pin for the raspberry pi to also run. > > It's not the flash chip drawing current, it's the rest of the mainboard. > > A PC mainboard has 10-20 different voltages. The 3.3 V rail with the > flash chip is only one of them. Each platform (CPU+chipset) defines a > strict sequence and timing for turning voltages on, for the platform > to function correctly. > > If the mainboard is otherwise unpowered and the 3.3 V rail is connected > to an external supply then that sequence and the timing is guaranteed to > be violated. This could cause anything from permanent hardware damage > (maybe unlikely, but certainly possible) to random malfunction, e.g. > excessive current draw, as long as the outside supply is connected. > > >> What is your recommended method for powering the chip and RPi? >> >> Looking online [1] some folks recommend using laptop AC adapter + >> wake-on-lan (and not using the VCC/3.3v pin), but I'm not sure >> that's a dependable strategy > > In fact I consider it the *only* dependable strategy. It is the > obvious way to adhere to the required power up sequence.
Thanks everyone for sharing their advice on this -- I can confirm that the Wake-on-LAN method works. If you are interested I have documented the full process of flashing an x230 with Heads: https://github.com/mfc/flashing-docs/wiki/Walkthrough-for-flashing-Heads-on-an-x230 -- Michael Carbone Qubes OS | https://www.qubes-os.org @QubesOS <https://www.twitter.com/QubesOS> PGP fingerprint: D3D8 BEBF ECE8 91AC 46A7 30DE 63FC 4D26 84A7 33B4
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