UFS1 Support on J5?

olearypa

For a carrier board design, we are investigating taking advantage of the UFS1 interface available on J5 of the VOXL2 for additional storage beyond that on board the SOM. Are there any gotchas we should be aware of? Would we need to make any device tree changes if we wanted to use it?

Moderator

@olearypa Hi, we asked around. It seems like it should work as is, but we have not confirmed or tried it

Vinny

Hi @olearypa
I suggest trying it on this board first: https://www.modalai.com/collections/expansion-board/products/m0062-2
That socket is a UFS/uSD combo mode socket and has the UFS signals on it: https://docs.modalai.com/m0062-datasheet/#j7---usdufs-combo-card-slot

olearypa

While we do have an M0062-2, UFS cards are like hens' teeth. Looks like eBay is about the only way to get one; Samsung seems to have stopped making them.

We did notice the SD_UFS_CARD_DET_N signal on J5 pin A12; is it reasonable to assume that we'd need to pull that pin low even if using a UFS chip (rather than a card) in order to signal the presence of the device?

Vinny

Hi @olearypa
Oh wow, you are right.
I guess UFS never took off since SD cards are so awesome now....
Last year these little sharkfin cards were easy to get...

I guess not so much anymore.

Sadly, I'm not sure how easy it is to design a plug-in board with UFS discrete since it requires other signals that we did not expose (given at the time UFS cards were abundant). The core 1.2V power rail is not brought to J5, and we have not verified if you do your own 1.2V supply that the power on timing will be satisfied. It's a risk to do it since we have not verified it, but give yourself an option to adjust power on timing if you try it. I'm not sure how the device tree needs to be changed, but I'm thinking there should be a way to indicate a non-removable device such that the DET signal is not needed. But, as a back-up, you should give the option to GND it as if it was using a socket.

olearypa

@Vinny For sure I think SD Express--with a major consumer device which uses them coming out in a week--won the very short lived MicroSD replacement war, even though UFS is (thankfully) taking over the internal storage market. Thanks for the hints; we'll see what we can come up with.