On 3 March 2017 at 17:19, Tony Lindgren <tony@atomide.com> wrote:

Sounds like we should do that ASAP. Care to send a patch for that?

Never mind!

I'm more familiar with (e)MMC than with SD and incorrectly assumed the card supply voltage is also its I/O voltage, but apparently an SD card is required to generate its I/O supply voltage internally, and this is switched to 1.8V by software command.

Now it all makes much more sense

main 3.3V ---[REGEN3]---> switched 3.3V to sdcard and LDO9

sdcard 3.3V ---[LDO9]---> host-side I/O supply

sdcard 3.3V ---[card-internal LDO]---> card-side I/O supply

Sorry for the false alarm.

There are still things that should be fixed to accurately reflect the schematics, including the use of REGEN3 to be able to power-cycle the card, but they are less urgent now and can wait until I've had time to test them.

Matthijs