SparkFun Forums

[nopepon]

Hi there,

I'm working on a carrier board for the RP2040 MicroMod (https://learn.sparkfun.com/tutorials/de ... 1599036432), and I swear I'm going crazy. Are there published mechanical drawings of this board anywhere other than this picture?:(https://cdn.sparkfun.com/assets/learn_t ... nsions.png)

Specifically, what I'd like to glean:
1. Precisely where to center my M2.5 standoff
2. How much of the board will be extending out of the M.2 connector when fully inserted
3. How wide the notch is
4. Radii on the various edges
4a. How much width is lost on the M.2 card edge due to the radii

Any help is appreciated on this. Hopefully someone has produced a proper mechanical draft, but at this point I'll even take someone with a board, some calipers, and a steady hand!

Thank you!

[TS-Russell]

The best info we have is either on that page https://learn.sparkfun.com/tutorials/de ... ssor-board or within a link on that page, such as the EAGLE files https://github.com/sparkfun/SparkFun-Ea ... croMod.lbr (we use AutoDesk EAGLE, download their free software and use the MicroMod library to view the files locally....you should be able to derive all the info you need form the various sources there (carrier board, standoff, etc) - it ends up being much simpler when you can navigate through a live model

[nopepon]

Thanks for the suggestion! I've downloaded Eagle and the MicroMod library, and now I have the parts in a board. Unfortunately, it's been years since I've used Eagle, and I've been spoiled by Altium (where I'm doing my current design).

I don't suppose and kind-natured users could help me out with the measurements I called out in the original post? So far, Eagle's "dimension" tool is proving too inaccurate for me to confidently take these values.

[nopepon]

Maybe even easier: Could any confirm the following measurements for me? I know these aren't exact, hence my frustration with Eagle's lack of precision (or my rustiness) in measurements.

I understand that the circle for the standoff is actually 6mm, and my 22mm dimension isn't even precisely aligned to the board.

Is the center of the 6mm standoff circle 7mm from the outer, right edge of the board?

Does the board insert 3.6mm into the M.2 connector (leaving 18.4mm exposed)?

Does the card edge of the board extend 1mm past the center of the M.2 connector alignment peg?

My ultimate goal here is just to be able to draw an accurate box on my Altium footprint showing how far this board extends out, as well as precisely placing the mounting hole.

[nopepon]

I've uncovered something very unnerving. @TS-Russell, is this something you can comment on?

The picture in my original post says that the MicroMod is 22mm from top to bottom. I discovered that you can export an Eagle board as dxf, which I then imported into Fusion360 to take more precise measurements. I've uploaded a picture below that shows the Eagle model (directly from the SparkFun library) listing the top/bottom dimension as 21mm!

Am I doing something wrong, or have I uncovered a grand conspiracy here? Needless to say, I'm feeling less and less confident in designing with this board, so it'd be great if someone official can actually confirm what's going on and what the measurements are, or if I should just plan to desolder the RP2040 and swap that onto the board I'm designing.

[TS-Chris]

It looks like some information was lost in your conversion process, the board is physically 22mm tall. I suspect your software is giving the dimensions for the area that has a copper ground plane on it rather than the actual total board dimensions.

MicroMod uses the M.2 standard with the key in the "E" position if that helps, the drawing below is a dimensional drawling generated by Eagle and should have the measures you need to reproduce the board.

Capture.JPG

[nopepon]

MicroMod uses the M.2 standard with the key in the "E" position if that helps, the drawing below is a dimensional drawling generated by Eagle and should have the measures you need to reproduce the board.

Capture.JPG

Oh yeah, that's the good stuff right there.

I am much obliged, Chris. This picture is exactly what I needed -- apologies that my Eagle skills weren't up to snuff enough to generate that myself.

For future me's out there, would your team consider adding that picture to the references section of the MicroMod webpage? And/or adding it to the reference manual? And/and/or/or converting it to an official mechanical drawing?

Once again, thank you very much for the reference!

[nopepon]

MicroMod uses the M.2 standard with the key in the "E" position if that helps, the drawing below is a dimensional drawling generated by Eagle and should have the measures you need to reproduce the board.

@TS-Chris one more urgent question for you (or anyone else who knows!)

I see this picture in the design guide, which seems to imply that the finger edge of the board ends up exactly in line with the top of the M.2 connector's mounting hole.

MicroMod_Eagle_Design_Mounting_Hole_Standoffs_Key.png

When I check the M.2 connector datasheet, it looks like it says the board will sit 1.75mm past the center of the mounting post. Can you confirm how far past the center of that mounting post the edge of the board will go?

M2 insert length.png

Modeled in Altium, this is with the edge 1.75mm past the center. It seems...too far.

MicroMod insert length.png

[MaffooClock]

I'm with @nopepon: been tearing my hair out trying to get accurate dimensions and coordinates on the processor card. Due to the lack of clear and thorough documentation, I'm very, very nervous about having my carrier board manufactured because I'm worried that my best guesses on placement aren't accurate enough.

@TS-Chris's screenshot in post #226155 is helpful -- certainly better than nothing, but there are a few points left unclear.

What I (and others, like @nopepon) expect to find right on the MicroMod documentation page (or even in the GitHub repo) are actual mechanical drawings, ideally in PDF format, so I can immediately read all of the pertinent information right in my browser while I design the footprint in Altium.

Anyway, I don't mean to complain, just reinforcing what was already said about the need for actual mechanical reference drawings.

[MaffooClock]

@TS-Chris one more urgent question for you (or anyone else who knows!)

I see this picture in the design guide, which seems to imply that the finger edge of the board ends up exactly in line with the top of the M.2 connector's mounting hole.

When I check the M.2 connector datasheet, it looks like it says the board will sit 1.75mm past the center of the mounting post. Can you confirm how far past the center of that mounting post the edge of the board will go?

I tinkered with this in Altium today and got the same result.

In @TS-Chris's screenshot, the screw hole at the top edge shows its inside edge to be 1.75mm from the 22mm edge (which is 20.25mm from the bottom edge). When I set a horizontal guide at 20.25mm, then align that 1.75mm cutout to it, the bottom edge of the card ended up in exactly the same place as what you found.

Further, when I switched to 3D view and set the connector to a 33% opacity, I could see the silkscreen line of the bottom edge of the card line up perfectly with the inner edge of the connector cavity.

Here's what I ended up with, and I feel pretty confident that it's accurate:

MicroMod M.2 Dimensions.png

MicroMod M.2 3D.png