USBridge Sig case: eMMC vulnerable

odonnell · October 23, 2019

The eMMC memory with its reader projects 1 inch from the front of the aluminum USBridge Sig case, and appears to be very vulnerable to accidental disconnection or breakage. Perhaps there is a jury rig shield that one might attach to the case. Complication: the reader partly obstructs the view of the green power LED, and a shield might hide it completely.

I'm pondering whether to switch to an SD memory chip to avoid accidents.

suzywong · October 29, 2019

Just curious. What benefit does eMMC have over SD?

odonnell · October 30, 2019

2 hours ago, suzywong said:

Just curious. What benefit does eMMC have over SD?

I'm not sure. I ordered eMMC because among the two choices offered for preloaded memory medium in the Allo online catalog, the eMMC was larger, and I had previous bad experience with SD. I've seen larger SDs elsewhere in the catalog.

I had previous bad experience with SD in a Raspberry Pi 3B+, where an accidental disconnection of an SD chip made it unusable (not recognized by another computer, as well as not working on the RPi). I hope that eMMC will be more robust, and someone from Allo seemed to suggest that in another topic that I can't find now. Even if eMMC is inherently tougher, it's not clear whether eMMC sticking out of the case is safer than SD well embedded in the case.

Advice from someone who knows would be appreciated.

bamyasi · October 30, 2019

Can you please provide a picture? I was unable to find any description or documentation for the eMMC option on the Allo.com site at all. So, I had no idea this is in the form of a card, in fact, my initial understanding was that eMMC storage is integrated into PCM module itself and is not removable.

odonnell · October 30, 2019

2 minutes ago, bamyasi said:

Can you please provide a picture? I was unable to find any description or documentation for the eMMC option on the Allo.com site at all. So, I had no idea this is in the form of a card, in fact, my initial understanding was that eMMC storage is integrated into PCM module itself and is not removable.

There are some pictures in the Allo catalog, but they are not explained clearly: https://www.allo.com/sparky/emmc.html

The eMMC memory itself is a boring rectangular item, almost square. I am pretty sure that it was originally designed to be attached to a connector in the middle of a board, but it can also be adapted to an SD slot.

The oddly shaped 7-sided thing in the picture, with "Micro SD eMMC Reader" printed on it, is the adapter to connect the eMMC through the SD slot. It has a rectangular area of pins, which is a male connector that fits a corresponding female on the eMMC device itself. I expect that this is the same connector that would be on a board with an eMMC module on it. You can probably see how the thinner protrusion on the adapter can slide into an SD slot.

This is the combination that I inserted through the slot on the case into the SD slot on the USBridge Sig. It sticks out a full inch, and has already been loosened accidentally by someone cleaning the area.

There is another adapter that came with the USBridge Sig, caseless. It receives the eMMC card rotated 180 degrees, so that the eMMC rests above the adapter instead of sticking out further. When the adapter enters the SD slot, the eMMC card rides above the SD slot. This seems much less vulnerable to me, but it doesn't fit into the case. I thought I saw a picture of this configuration somewhere, but I can't find it now. When I received the caseless USBridge Sig, the eMMC card was connected in this second way, with the 7-sided longer adapter separate. It took me some time and hunting through pictures to realize how to remove the eMMC card and reattach it to the extra adapter.

I was able to run the caseless USBridge Sig in both configurations of the adapters, but only one of them fit with the case. I was rather afraid of breaking something when I detached and reattached the eMMC card from/to the adapters, but it turns out to work rather easily.

odonnell · October 30, 2019

Key to the pictures at https://www.allo.com/sparky/emmc.html

There are 5 pictures but you have to click on one and use sideways scrolling arrows to see them all. From left to right:

1 appears to be a rectangular adapter different from both of the ones I received with the USBridge Sig.

2 is the eMMC card attached to the adapter from #1. The eMMC card is a duller gray than the adapter, slightly smaller, with "SAMSUNG" printed on it. The connectors are hidden between the card and the adapter.

3-5 appear to be the case-compatible connector, from three different angles. Instead of attaching so that it hovers over this adapter, the eMMC card overlaps but sticks out well beyond the wider end of the adapter.

The alternate adapter that came with the USBridge Sig is narrower than the eMMC card, almost rectangular, its narrower dimension fits into the SD slot. It connects to the eMMC card sort of like picture 2, but in this case the adapter is smaller than the eMMC card. When the adapter slides into the SD slot, the eMMC card rides above the slot.

odonnell · October 30, 2019

WARNING ABOUT ORIENTATION OF THE CONNECTORS:

The connectors look symmetrical to my eyes (which are not good for close up work). But, I think they are probably not safely reversible.

I have no idea what happens if you attach in the wrong orientation, and I don't care to try.

I received the eMMC card connected correctly to the smaller adapter. When I changed adapters, I inspected both closely with a magnifying glass. I saw some pin labels around the connectors on the adapters, so I turned the eMMC card 180 degrees to match those pin labels in the same way. That worked. The other direction might work, might be impossible to do, or might be possible but damaging.

Again, advice from somebody who really knows would be appreciated.

odonnell · October 30, 2019

The picture on this catalog page shows an eMMC card connected to the larger adapter and plugged into the USBridge Sig through the slot in the case: https://www.allo.com/sparky/usbridge-signature-player.html

You have to click the picture, then scroll to the right. The second last picture shows eMMC, the last picture shows the (almost invisible in the slot) SD card.

Still haven't found a picture of the eMMC card connected to the smaller adapter.

bamyasi · October 30, 2019

38 minutes ago, odonnell said:

The picture on this catalog page shows an eMMC card connected to the larger adapter and plugged into the USBridge Sig through the slot in the case: https://www.allo.com/sparky/usbridge-signature-player.html

You have to click the picture, then scroll to the right. The second last picture shows eMMC, the last picture shows the (almost invisible in the slot) SD card.

Still haven't found a picture of the eMMC card connected to the smaller adapter.

They must have added this particular picture with the eMMC inserted into SD slot in the case recently. It was not on the page a few days ago. Thank you for pointing this out to me. I agree this configuration looks odd and probably not very safe in a long run. Seems to be an afterthought. Typically, you would prefer eMMC since it is faster and orders of magnitude more reliable compared to SD. But this ugly poking out card might make me reconsider.

suzywong · October 30, 2019

20 hours ago, odonnell said:

The picture on this catalog page shows an eMMC card connected to the larger adapter and plugged into the USBridge Sig through the slot in the case: https://www.allo.com/sparky/usbridge-signature-player.html

You have to click the picture, then scroll to the right. The second last picture shows eMMC, the last picture shows the (almost invisible in the slot) SD card.

Still haven't found a picture of the eMMC card connected to the smaller adapter.

Yes, I see what you mean about the eMMC card sticking out. I can foresee a wayward paw belonging to a tortie Burmese landing with force on it - one broken card later.

I've always used Sandisk 16GB SD. For sure I've lost a couple, but at around a tenner apiece, I'm not going to lose any sleep over them.

Indeed, when I recently moved my DigiOneSig from the Rpi3B+ to the USBridgeSig, I simply pulled the SD out of the Pi and plugged it straight into the USBridgeSig - and that was that.....(software is MoOde)