Since the Dogwood schematics are now listed as version 1.0.0, I assume that there won’t be many changes until Evergreen.
I went through the schematics for Dogwood and made a list of all the components, that aren’t generic resistors, capacitors, inductors, etc. for each page in the schematics and added links to their datasheets and gave a short description. This will make it much easier for people to find out what are the chips when reading the schematics.
In the schematics, there is a floating comment with three Micron parts that I assume Purism was considering using, but didn’t. One of them was for 4GB RAM. I’m sad that part wasn’t included in the Librem 5.
Thanks for writing this up. It should definitely go in the hardware reference at some point.
Adding this to the hardware reference would be great. There are couple unidentified 6-pin chips in the schematic, plus a 4-pin one. It would be nice if Purism would identify them for us, or just post the parts list, so we can figure out what are the mystery chips.
I just added the parts for the USB-C board as well, and it has a 28-pin connector that I can’t identify either.
Here are the couple mystery chips which I can’t identify:
Unidentified 12-pin chip (pins: A1, A2, A3, A4, B1, B2, B3, B4, /0E & GND; 4 pins are unconnected)
CQ3610BL-100 unidentified 3-pin IC in PWM2
Unidentified 6-pin chip labeled as “NC” (pins: VOUT, GND, ON, VIN, GND, VIN)
I googled “NC” and found out that it means “not connected”, so chips U3, U50 and U51 aren’t being used.
So the only remaining question is what is the purpose of the CQ3610BL-100 IC?
LuluColtrane on reddit answered my questions about the purpose of the unidentified chips:
In the old days, an NC pin was often used as a diagnostic connection by field service tech.
If they wanted them for diagnostics, they probably would have labeled them as test points.
According to LuluColtrane, Purism probably has these “NC” parts as options in the PCB in case the default parts don’t work. Purism can take off the default parts and solder on the “NC” parts instead.
For anyone who cares to do a comparison, I have also posted the component list for the PinePhone:
The schematic for the Librem 5 is 2-3 times more complicated than the PinePhone’s schematic. I’m not sure if Pine64 is hiding some of the details or the Librem 5 is simply a much more complex device.
the steps taken by Purism to isolate the modem firmware from the main CPU are probably part of that equation …