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Bug #4782

ngff-breakount doesn't work for RM500Q

Added by laforge 14 days ago. Updated about 1 hour ago.

Status:
New
Priority:
Normal
Assignee:
Target version:
-
Start date:
10/07/2020
Due date:
% Done:

0%

Spec Reference:

Description

It seems that (at least) Quectels first 5G modem in ngff form-factor (RM500Q) is a longer card type than what we designed the ngff-breakout for. Its width is 30mm, the length excluding connector is 48mm, (including connector: 52mm).

I would expect that more 5G modems, at least in the "early 5G days" actually will need this larger form-factor. This should be confirmed looking at [preliminary] data sheets.

I suppose we need to do a board spin with a larger PCB. That larger version then needs slightly more space between the NGFF slot and the 2.54mm pin connector, and a second SMT spacer for mounting the screw there.

While at it, we might also consier adding a 4th SMA connector, as the RM500Q now has four antenna connectors (MHF4)

20201007_101506.jpg View 20201007_101506.jpg 175 KB laforge, 10/07/2020 08:16 AM
20201007_101521.jpg View 20201007_101521.jpg 1.17 MB laforge, 10/07/2020 08:16 AM
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History

#1 Updated by mschramm 14 days ago

We designed this PCBA with M.2 3042 form factor modem cards in mind. The RM500Q is a 3052 M.2 card. I'd be easy to make that spin, but while Quectel, Simcom and SierraWireless 5G modem are 3052 M.2 cards, Telit offers a 5G M.2 modem (FN980m), advertised as being a 3050 card...

So for these 2mm difference surely a third SMT screw post wouldn't be possible. I just imagined an oblong hole / slot instead on n seperate posts, maybe we could hold a single of them movable it w/ a second screw+washer from bottom side.

#2 Updated by laforge 14 days ago

Let's go for the 3052 case. If Telit wants to do their own thing... so be it. I guess
they will have a hard time convincing mainboard manufacturers etc. to accomodate their special
form factor.

#3 Updated by mschramm 13 days ago

re Telit: they seem to be serious with their 3050 ff, OK, their problem.

More important:

  • it appears, that we need to support more than one length option. Then the SMT posts should not get soldered, but fixed in either of two or three positions w/ a mandatory screw(+washer?) from bott side. Likely the screw's flat pan head will do without an additional washer.
  • when touching this project, I'd like to exchange the pinheader area with the RF SMA-MHF4 area. This would also ease the space for a fourth SMA.

#4 Updated by ben.foxmoore about 2 hours ago

We (at Accelleran) have been developing our 5G SA software, and have noticed similar issues with the Sierra Wireless EM9190 and the M.2 - USB adapters available on the market today. It seems that your design has the same problem. Is there a plan to re-spin this design allowing for the 3052 format cards?

I'm aware that Sysmocom and Osmocom are not the same, but I know that batches of this design are sold by Sysmocom. If there's a question of MOQ, then we may be interested in committing to an order of a small number if that helps at all.

#5 Updated by mschramm about 1 hour ago

ben.foxmoore wrote:

It seems that your design has the same problem.

It is not a problem itself, it just results from several design decisions by the modem manufacturer and by sysmocom when first selecting interesting modem cards for such a break-out. At that time, no 5G cards were available, and the desired 4G cards are/have been 3042.

Is there a plan to re-spin this design allowing for the 3052 format cards?

Yes, right now I prepare a spin of that design for supporting 3042 and 3052 cards. If we decide to use an oblong hole for the SMT stand-off, this will support also 3050 modem cards; however, 3042 and 3052 are mandatory.

I'm aware that Sysmocom and Osmocom are not the same, but I know that batches of this design are sold by Sysmocom. If there's a question of MOQ, then we may be interested in committing to an order of a small number if that helps at all.

Appreciated, I know laforge listens.

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