Extra eyes on ESP32 Reflections ThingTwo main board?

I found the schematic difficult to follow as well.  For example, below is the GPS which is labelled "50 OHMS IMPEDANCE" instead of GPS.  I had to look up the part number to see what it was.  I was interested in seeing what the GPS schematic looked like because the previous version was said not to work.

The pin marked "ON/OFF" is not connected.  I'm not familiar with this part and don't know if that is acceptable or not but it should show a connection or be marked with an X flag to indicate it has no connection.  There are several other pins like this on the schematic and the design rule checker should be issuing warnings.  Ideally the GPS would be tested / prototyped before adding to the larger project which would reduce wiring and code errors.

Have you had a good look at the power budget?  There won't be much room for a battery and some of the components are likely to be power hungry.  

I found the schematic difficult to follow as well.  For example, below is the GPS which is labelled "50 OHMS IMPEDANCE" instead of GPS.  I had to look up the part number to see what it was.  I was interested in seeing what the GPS schematic looked like because the previous version was said not to work.

The pin marked "ON/OFF" is not connected.  I'm not familiar with this part and don't know if that is acceptable or not but it should show a connection or be marked with an X flag to indicate it has no connection.  There are several other pins like this on the schematic and the design rule checker should be issuing warnings.  Ideally the GPS would be tested / prototyped before adding to the larger project which would reduce wiring and code errors.

Have you had a good look at the power budget?  There won't be much room for a battery and some of the components are likely to be power hungry.  

I feel the same as Frank, it's hard to follow, with upside-down earth symbols, and in places there were wire labels hanging off corners.

Something's not right if this is the third iteration and it couldn't be made to work on the previous two. The very first PCB should work, albeit a few bodge wires may be needed on the first PCB. If it cannot be made to work on that first PCB (with bodge wires/cut traces and so on), it's a DEFCON 1 level situation.

You mention the GPS didn't work, and it has been replaced with a different module. As Frank too suggests, has that been tested in a prototype? (By prototype, it means just tack wires to it if necessary, and solder it to your board). It's best to go into a PCB design with close to 100% confidence that it will all work. Unless it's a really simple design, I don't think I've ever made a PCB design without at least some prototyping, on stripboard or whatever, or (if it's easy to do so - not the case with a GPS module) simulation. 

If the engineer can make the schematic tidy, the process of doing that may reveal issues to them. Also, a design review (where they talk it through with you - it doesn't matter if you are experienced or not, it will help the engineer discover bugs merely through talking through their design (they could talk it through to a cat if necessary! although it's best discussed to a human, so that you can ask simple questions, and you don't need to understand the response, provided it sounds like a well-reasoned response).

Also, there's still an inner-layer ground plane around the module, and that's been discussed multiple times, so the fact that it has not been picked up as an issue, means that there has been zero design review, because that review would have been the opportunity to ask why it's still present on the third release of the board.

"For example, below is the GPS which is labelled "50 OHMS IMPEDANCE" instead of GPS. " I take your point, and well. I will work on cleaning up the silkscreen overall. And to your point about the impedance label it applies only to Pin 11 RF_IN. I'm changing the label and denoting GPS for the module.

The Sox (rev 1) and Hoober (rev 2) GPS modules may have worked; However, the boards has so many fundamental problems - like Sox ESP32 not booting. I tested the ATGM336H-5N31 in a breadboard and it works great. It comes in a surface mount module, so much less testing and I chose it. 

"Have you had a good look at the power budget?" Measuring current needs is coming up next week. I will report what I learn here.

Hi Shabaz, "Something's not right if this is the third iteration and it couldn't be made to work on the previous two." I had planned to do 3 revisions of the board (Sox, then Hoober, then ThingTwo), with reworks (cut traces, soldered wire) on each. So far that has worked well, including Hoober mounting as a hard drive and later displaying videos on the display at 10 Frames Per Second. I'm feeling good about where we are at. -Frank

Thanks for the pointer on the ground plane, I'll make sure that gets attention. -Frank