On Mon, Sep 19, 2016 at 12:07 PM, TsvetanUsunov <tsvetanusu...@gmail.com> wrote:
> We make our final touch of A64-OLinuXino PCB and there we add option eMMC
> Flash to work on dual voltages 1.8V and 3.3V.
> The eMMC is connected to AXP803 pin.34 GPIO1/LDO. The problem is that when
> A64 boots and AXP803 is not initialized it outputs default 0.8V then after
> initialization driver takes care to drive it 1.8V or 3.3V.
> This makes impossible to boot from eMMC which is not good. We now think for
> solution which to drive eMMC at 3.3V initially when AXP803 output is below
> 1.8V but this adds unnecessary hardware complexity.
> For hardware point of view it will be much more simplier if dedigated A64
> GPIO is used and initially is pulled down and after AXP803 is initialized is
> pulled up.
> How would you suggest us to implement it? Will this additional GPIO create
> troubles in eMMC driver philosophy?
> For the SDMMC we are still hesitating what to do as we don't know if the
> card which will be inserted will support low voltage and higher speeds at
> all. Also eMMC Flash and SDMMC card should be driven by separate voltages,
> as they may work in any combinations.
> This means we need another AXP803 LDO and another GPIO for the SDMMC card.
> By the way the current eMMC from Micron we use has 11MB Write speed no
> matter what is the voltage and this is written in the datasheet, so maybe we
> should switch and add this dual voltage to the SD MMC where someone could
> use SD MMC card supporting higher clocks?
Does eMMC exist with the higher speed 1.8V option?
I know some SD Cards support it.
> I would love to hear your opinion.
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