For the CM4 is there really any reason to lift motherboard WiFi chip or cut traces on the motherboard? Im still pretty new to hardware mods like this so im wondering if im missing something.
The CM4 attaches to an adapter that then plugs in to the SODIMM socket on the motherboard, that means all of the connections are right there in the open on the edge of the adapter. My idea is to solder jumper wires to the very top of the GPIO pads and cover the rest of the pad with solder mask or kapton tape so they never get to the motherboard in the first place. I figure this way my motherboard is fully functional for other cores.
Is there any reason this wouldnât work compared to cutting the traces on the motherboard or lifting that chip?
If you do not have access to hot air, even just removing power from the MB WiFi (cut one single trace) may suffice actually. If the chip does not power on, no data is transmitted and the bus is free to use for GPIO.
Yes, hijacking the signals would work as long as they donât make the connection to the MB. But to make sure that doesnât happen you still need to cut the traces on the adapter before they get to the connector or after they leave the connector on the MB, assuming they are accessible. Youâll have to check the schematic for the MB, adapter board and compare them to the physical boards to see if it can be pulled off.
In short you need to study the schematics and physical boards to see if this can be done.
And there is still the question of whether or not the adapter board exports the needed signals to the MB socket. This is called in to question by what you mentioned about needing a CM4 with WiFi. This is all moot if those signals are buried on BGA pins of the SOC. Most SOCs Iâve looked at use BGA pins. Iâd have to look at the CM4 to know if it does.
I donât understand; if we power down (cutting power or GND trace) or remove the WiFi module from the MB, the GPIOs on the 40-pin GPIO header are going to be free to use, no?
You mean balls?
Itâs nice / comforting to see though, that the CM4 has a nice antenna connector just like the Clockworkpi MB, so you can still connect antennas (maybe even the included one) and get good reception.
It may be worth breaking that connector out to the shellâs outside to connect a beefier antenna via SMB, though. Applies to the MB WiFi, as well, of course.
Another question, referring back to the original post: canât you use the â52 Pins extension module interfaceâ? Is there anything preventing you to use that for the RTC?
From what I can tell here, GPIO28 through GPIO44 are free to use on the PCIe slot, right?
And if you do remove the WiFi chip, you get full 19 GPIOs free on the â40-pin GPIO headerâ:
If you end up needing the MB WiFi module after all, you can get a second MB for just $39. Then youâd have one WiFi MB and one non-WiFi with 19 free GPIOs.
Another idea: if you populate the mini PCIe slot for a 4G module and donât want to lose MB WiFi, you do get another audio port on that 4G module. So you could remove the MB audio and get 4 GPIOs, in case thatâs enough for you:
Yes, if you remove the WiFi module you gain the GPIOs. But that wasnât the question @USFrozen was asking. I would also say that I would have some concern that an unpowered WiFi module sitting on those lines might inject some noise. But my understanding of how the chips are actually made is extremely minimal, so it could very well be a good solution.
Assuming that the CM4 adapter is actually providing those signals. I have not attempted to verify that either.
Yes, I want the printer, speakers and USB ports so I want to leave the âext moduleâ intact and connected. The I2C bus for the EXT module is brought out on the camera port. I donât see anything on that board interfering with address 68H. Since I have no desire to have a camera my plan is to tap into that. Its just going to take more time, ducking and probably more creativity.
To clarify my specific needs: I just need access to an I2C bus⌠which is usually stupid simple. Imagine my surprise after finding and ordering pieces to work with these awful connectors that it didnât work. Turns out the devices on the MB attached to the I2C bus also use address 68H. And there is nothing I can do about that.
The whole point of this topic was to start the discussion about what GPIO was actually still available on the so-called GPIO connector and to act as a warning for others looking to take advantage of it. Mission accomplished!
âBallsâ / âpinsâ same difference. I italicized the word because its not the exact correct word to use. But even novice readers will likely understand what I wrote.
Good point; sadly I just discovered that the CM4 adapter has no schematics or PCB files on GitHub (yet?).
In case they thought of that (that the CM4 has WiFi already) and left the GPIOs free, that would be great news for CM4 users.
I agree, and I do thank you for that. Itâs very good to know that this issue exists.
I italicized the word because its not the exact correct word to use. But even novice readers will likely understand what I wrote.