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i.mx6ull storage options?

Question asked by David Luberger on May 22, 2018
Latest reply on May 23, 2018 by David Luberger

I'm in the beginning stages of developing my own custom board with the i.mx6ull. I'm following the eval board schematic and reference design, and among other issues like component availability and substitutes, I'm trying to decide which flash memory type to use for storage and running the OS.  There's almost no information at all in the datasheets or manuals that might help me decide which route to take.  The only thing I know is that I'd like to avoid using an SD card because I don't want my finished product to have a removable SD card (we have another product already that uses an SD card and it's been a nightmare, as it seems not all SD cards are created equal, and finding a good holder and bulkhead feedthru method has been difficult).  So it seems like eMMC is the way to go, but availability seems to be really low on these.  The manual says it supports up to eMMC 4.5 but the only ones I'm finding with consistent availability are eMMC 5.0; I'm assuming they're backward compatible but I can't really tell. Also, the reference design schematic table for the boot config settings is really convoluted and confusing, as there are many different options and settings, much of which isn't obvious looking at memory datasheets to tell what the right settings are (e.g., mmc 4-bit bus width vs. 4-bit DDR bus width; I haven't seen "DDR" mentioned on any MMC/eMMC datasheet at all).  Also, it seems capacity is a limiting factor, but if SD cards are available cheaply in 32GB+ sizes, why aren't individual flash memory ICs available cheaply as well? and why can't i find nand flash in large capacities?  I feel like my hand is being forced in terms of storage memory type (all signs point to SD card in terms of cost and availability), so is there really no good alternative? I'm assuming since I'm just following the yocto project guides I'm going to need gigs of space; going with megabit-scale storage just seems like it won't be a good fit. I feel really lost and confused...