I am investigating the lasts bug I had with my custom board. I stil have bad behavior of PB18 and PC19 after reset and before instantiating these IOs as output. But today I am facing an other problem. I have discovered long time ago that the CR2032 used to save RTC was not functionning properly on my custom board while it was working well with the G400HDR.

On my custom board, as soon as the CR2032 is inserted, its voltage drops down bellow the minimum voltage required to save the RTC. Therefore, there’s something wrong with my schematic. And current is drawn by the SOM. I discovered by using the G400HDR that when VBAT is applied, the PINs 179 (SHDN) and 177 (WKUP) are at 3V!

I go back to my documentation brochure; these pins are well described as SHDN and WKUP that’s why I have connected SHDN to GND and WKUP to VCC. Today in the G400D documentation these pins have been removed!!!

What’s happened there? What to do with these pins?

Please do not connect these pins

Yes I read that! This is important and should be reported in the GHI doc.

And its only after measuring voltage on these pins that I discover the problem. One could think that SHDN and WKUP were input to shutdown /wake up the SOM (these pins were mentionned in the 0.07 brochure and suddenly disappear without any announcement…) . As input SHDN would have been pulled down, and WKUP pulled UP! And this is not the case! This is a serious lack of information! Again ten PCBs to throw in the bin! this is the second time! Too much time and money spend with such things!!! Sorry for being rude but we have started to move from EMX to G400 a year ago. Of course we are not 100% of time on that but on 3-4 years with EMX and G400 we have too much issues, most of them are from our own but would not have been made with better documentation!!! At least now they are not even mentionned.

I am happy to find the cause but also really disappointed… Am I the only one who have so much troubles during design phase?

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Too late…
[ :wall:

Someone at GHI discover that these ones shouldn’t be connected and removes them from the pinout desc. Why did he not made an annoucement at that time… :wall:

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We never said to connect them and the raptor schematic didn’t include them. Sorry about the confusion and we are always here to cover any questions you may have.

The good news is that now we offer development boards, which are also reference designs. The new datasheets are also clearer and have more details.


GHI have never said to not connect them before neither …


I’ve been running a number of G400-D modules with the WKUP pin connected direct to ground. The SHDN is unconnected.

What is the issue with the WKUP being tied low? Will this draw power from the backup battery? It may explain why a board left on the shelf for a year had a dead battery when it should have lasted longer than this. Bit of a rats to get to the track and cut it as it is under the socket. :frowning:

What’s the status on another pin, 181 which on my old schematic is PWR_EN which I have connected to GND.

One of the issues with my design is that I migrated from the ChipworkX and the G400 was quoted as being compatible bit it seems there are issues and I don’t see any docs on this. ChipworkX for instance states that pin 177 (WKUP) should be pulled to ground if not used)

For pin 181 (PWR_EN) this is for the 1.2V sleep and I assume this pin is simply unconnected on the G400 module?

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Hi Dave I am in the same situation, but I cant easily cut the wire on the PCB. I found something easier. It is possible to remove the pin directly on the DIMM socket.

On my old documentation of G400 pin 181 is described as PWM_EN not PWR_EN :open_mouth: again this pin has disappear in the last datasheet…

It was stated as a drop in replacement for the ChipworkX hardware wise but that doesn’t seem to be the case. We need to know what is different as I am re-stringing the PCB design this week.

So current datasheets along with the reference development board schematic doesn’t cover everything you need? What info are you missing?

I guess he need an exact documentation in terms of explicit/implicit differences betweeb both SOM. The already mentionned pins are ones of the such differences

Actually, no it does not. For instance your G400D dev board shows the WKUP and SHDN pins as unconnected for sure but there is nothing in the documentation to indicate why? In fact, those pins, 177 and 179 are shown as blank in the actual datasheet. We have to delve into the processor datasheet to find more but who is to say you don’t have additional circuitry on your G400D module that we don’t know about. Same as for PWR_EN (181), there is nothing in your datasheet for this pin (it’s blank), yet it is shown on your G400D dev board schematic just like the other 2 above. No mention if this is actually used on the G400D or not. This one pin appears to be legacy from the ChipworkX module but again, it would be nice to know that this is not connected on your board.


OH Yeah, this is just a little rant because I actually love the G400D and just deployed one with a friend of mine in Texas and I have another project on the desktop that a client has just requested. This module rocks but we just need good quality datasheets to be 100% sure our designs will be good. Right now, my only concern is the battery drain that leforban noted on the units I have already deployed. Luckily they are powered 24/7 so I may not see it but we should know about it :slight_smile:

While the G400D and G400S both label SHDN, WKUP, and PWR_EN, none of them are connected on either board. The datasheets do not detail those pins because they are to be left unconnected so no further information needs to be given on them.

If you have an existing design with these pins in question connected, contact us and we will proceed from there.

Thanks John,

If they are physically not connected on the G400-D module then there is no issue at all. Just wanted clarification on them that was all.

He meant they are not connected on the reference design, the development board.

You should not connect these pins as stated in the datasheet and the reference design. If you have a current design with any of these pins connected then contact us to look into it but your future updates to the design should not connect them.

I have boards where they are connected. This was resulting in CR2032 that was empty after just feew weeks…

I have removed the pin directly on the socket and things are better now

I understand that now Gus but remember that GHI stated that the G400 would be a drop in replacement hardware wise for the ChipworkX so any hardware differences need to be indicated. The WKUP pin is documented for the ChipworkX so that is why it is connected on my board. If they are not needed on the G400 at all, it would have been better that they were not physically connected on the edge connector. :slight_smile:


The question could then be : are those pins used “internally” by GHI in a way that would prevent their use in other designs.

If they are not used by GHI, then I do not see any reasons to not use them for what they are supposed to do.


@ Dave McLaughlin - the pins are available but should not be connected. If you need them connected then contact us privately please.

@ Gus : this is a rather contradictory statement… If pins are available, then why would not we connect them ?

Are those pins used internally by you for something, thus preventing their use by others ? This is important to know for a SoM that is intended to be used in custom designs.

Moreover, those pins have a real interest and are documented in the MCU datasheet. So, what is wrong with those pins ?

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