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-...
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Michael Carbone