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<d1b2>
<esden> Ok rounded up all the part for the top side. (these are just the ones I will place by hand, the ones placed by the machine are already set up)
<d1b2>
<edbordin> * looks guiltily at unpopulated revC1 board *
<d1b2>
<OmniTechnoMancer> I feel a desire to have a glasgow, but doubt I could perform assembly
<d1b2>
<edbordin> I have been tooling up so that I can practice some assembly but I am a real procrastinator
<d1b2>
<OmniTechnoMancer> I also have an extreme lack of PCB assembly tools past what might be useful for through-hole or large smt
<d1b2>
<edbordin> * looks even more guiltily at reflow oven and stereo microscope *
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<lukego>
okay time to hook up my PCBites oscilloscope probes and have another poke at the glasgow board. I wanted to hook my scope up to the computer via ethernet but am a bit too lazy to package the relevant software for nixos just right now.
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<lukego>
I really need to revisit some life decisions vis-a-vis relatively placement of test equipment and device under test.
<d1b2>
<martinr> any progress with tracking down the fault?
<lukego>
no, just been sharpening my pencils so to speak, getting a better probing setup
<lukego>
I'm actually a bit stuck now trying to understand how the PCBite oscilloscope probes fit togehter
<lukego>
(turns out you just have to push them hard to "click" but that wasn't clear from the instructions and I needed to look under a microscope to convince myself)
<lukego>
now I put my oscilloscope into some long full self calibration process when I think I only wanted to quickly bias for a new probe... n00b problems.
<lukego>
okay let's be all serious and make a custom USB power cable that connects to the bench supply
<lukego>
okay, I've made up the cable and setup the probes, and still have *ahem* a few minutes left to try and check a thing or two
<lukego>
I'm not expert at reading an oscilloscope but it looks like 1V2EN is seeing a short sharp 100mV spike every 100us.
<lukego>
I'll now probe 1V2EN and +1V2 together and see how they behave, and whether shorting 1V2EN to 5V changes +1V2
<lukego>
Good news is that I have a setup for powering and scoping now. Bad news is that I wasn't able to get sensible data in the first session. I'll try again when I get a chance. Might have to do a few basic exercises with the oscilloscope to see if I'm reading it right, just now the values would make much more sense if they were 10x higher. Maybe something to do with this probe.
<lukego>
okay, yes, the PCBites SP200 is a "1:10" probe so I was getting sensible values but attenuated by the probe. So I guess the next step is to get the scope to boost them 10x so that I don't have to mentally compensate
<lukego>
oh yes and there it is. Cool. all setup but the dog isn't taking "no" for an answer on this walk. Please excuse the stream of consciousness ^^
<d1b2>
<Attie> well done with the probe attenuation 🙂
<d1b2>
<Attie> if you're still at it, then an image (good photo, or screenshot) would be helpful
<d1b2>
<Attie> "100mV spike" is missing some details - from what to what? sharp edges? etc...
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<lukego>
okay, what I'm seeing right now is very consistent, albeit different to what I said before :) --
<lukego>
1V2EN is steady at 4V8 and 1V2+ is steady at 0.2V
<lukego>
I tried shorting 1V2EN with 5V and that had no effect, which I suppose is not surprising since its base level is now 4.8V instead of the lower/unstable value that I saw before. I can't account for the change at the moment.
<lukego>
10mA draw and the only LED that's on is PWR.
<lukego>
(time to put the kids to bed...)
<d1b2>
<Attie> very frustrating... I can't remember if you have yet, but might be worth replacing the regulator?... also worth trying to figure out what's going on re: different behaviour
<electronic_eel>
lukego: I don't remember everything you wrote in the last sessions, maybe you already found out - but is there a short on your 1V2 rail or not?
<electronic_eel>
lukego: I suggest soldering a wire to the 1V2 testpoint and then hook up a bench supply to it. set it to 1.2 V and something like 50 mA current limit
<electronic_eel>
if your bench supply also goes into current limit, then you have a short on the 1V2 rail
<electronic_eel>
if the 1V2 rail comes up to 1.2 V without going into current limiting, then the regulator is probably at fault
<d1b2>
<Attie> @electronic_eel - good call re feeding 1.2v from a bench supply... however with 10mA into the USB connector, I wouldn't expect a short on 1V2 - does that sound like a reasonable expectation to you?
<electronic_eel>
oh, just 10 mA draw from usb? that doesn't sound like a short to me.
<electronic_eel>
it could be if there were some kind of hiccup mode in the regulator, but I don't think this ldo has hiccup
<electronic_eel>
if there is no short on the 1V2 rail and 1V2EN is high, my next guess would be a soldering issue on the 1V2 regulator
<d1b2>
<esden> Will be going live on twitch in a few. We will assemble the top side of the revC2 prototypes. 🙂
<electronic_eel>
esden: nice, thanks for the heads up
<d1b2>
<esden> Just finished confirming that the orientations I programmed in the PnP are correct. (ran into a profile issue for the level shifters, that is sorted out now too)
<electronic_eel>
oh, those ics look lonely on the pcb. you should add some more to make them happy :)
<lukego>
Thanks for the ideas. I'll refer to the irclog when I get a chance to take a next look!
<electronic_eel>
lukego: a soldering issue on the regulator could also explain the different measurements on the 1V2EN you got. it could depend on pressure or bending you put on the board or ics