<tnt>
marcan: not necessarely a good idea. Depends on the strength I guess. Because just because an applet doesn't use a pin doesn't mean it's not connected. I have a glasgow connected to several parts of a DUT and run one or the other applet depending on what I want to do withough changing connections and I expect the other pins to be undisturbed.
<eddyb>
whitequark: so from what I gather there was an intermediate period between bipolar TTL and CMOS in which higher-density designs used NMOS? so I won't find an NMOS logic 74xx, but rather some CPUs and sound/video chips?
<whitequark>
i don't know
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<marcan>
tnt: obviously it would have to be configurable, but I'm guessing a 10K pulldown by default on unused pins may not be a terrible idea?
<marcan>
Obviously if you need to turn it off you should be able to
<marcan>
It's just a software thing
<marcan>
Pulldown is safer since pins may be connected to logic with a different standard from Vio (e.g. for input only use)
<tnt>
yeah if you can disable it it's fine.
<marcan>
whitequark: so, make all the resistors 33Ω, check on that silkscreen art issue, anything else before cutting revC1? esden: do you want to do a DFM review?
<tnt>
tbh a way to specify the pin state from the CLI independently from the running applet would be nice.
<marcan>
Yeah
<whitequark>
marcan: there's the port power LEDs
<whitequark>
#127
<marcan>
Ah yes
<_whitenotifier-1>
[Glasgow] whitequark opened issue #128: Design better API for adding registers - https://git.io/fjmdQ
<_whitenotifier-1>
[Glasgow] whitequark commented on issue #128: Design better API for adding registers - https://git.io/fjmd5
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<G33KatWork>
ohai
<G33KatWork>
I am currently filling a digikey shopping cart to build a Glasgow C1
<G33KatWork>
the caps with the u1 values are 100nF, I guess?
<G33KatWork>
because the part number in the kicad schematics point to a 150nF cap
<G33KatWork>
and they are not in stock, so I want to replace them with some others
<davidc__>
G33KatWork: all the u1s I can find are just decoupling
<davidc__>
so probably easy to sub with whatever
<G33KatWork>
yeah, I figured, I just got confused
<G33KatWork>
thanks for checking
<gruetzkopf>
G33KatWork: do you have a glasgow already?
<marcan>
G33KatWork: the BOM for C1 needs review, make sure any partnos indicated actually match the schematic value
<marcan>
and all the protection resistor packs missing values are 33Ω
<marcan>
G33KatWork: also might be good if you can independently confirm footprints for the ICs
<marcan>
davidc__: yeah, I think the only capacitors in the whole design are the xtal caps, the ADC filter caps, and the rest are decoupling in a few values
<G33KatWork>
marcan: yeah, most of them don't match
<marcan>
PRs appreciated if you want to do some of the grunt work :-)
<G33KatWork>
I'm a bit in a hurry with my current digikey order. I'll complete it, order stuff, print out the PCB on paper and sanity check everything that way
<marcan>
heh, sure
<G33KatWork>
stuff that won't fit will find its place in the holy parts bin
<G33KatWork>
for times when you need that one part, have a full box on a shelf and you still don't have that one part you need
<marcan>
:-)
<tnt>
I recently upgraded to parts folders so I keep better track of what I have :p
<G33KatWork>
huh. what's the ATECC508A
<G33KatWork>
for?
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<gruetzkopf>
i have so many parts drawers
<whitequark>
G33KatWork: traceability
<G33KatWork>
oh, for genuine devices when you sell them?
<electronic_eel>
marcan: whitequark had some issue with the enable of the vreg acting weird on saturday. were you able to reproduce it?
<marcan>
G33KatWork: yes, traceability
<G33KatWork>
meh, the MIC5355-S4YMME isn't in stock and the MG2048 isn't even sold by digikey. apart from that everything is available
<marcan>
and also unique serial numbers (we decided to change the scheme)
<marcan>
only software impact is it'll tell you who made it if properly provisioned (none of this is implemented yet)
<tnt>
G33KatWork: MG2048 ?
<G33KatWork>
tnt: U33 and U35 according to the BOM
<marcan>
G33KatWork: uhh that's a stupid typo
<marcan>
MG2040
<marcan>
thanks for catching that :p
<G33KatWork>
oh nice
<G33KatWork>
I just opened the datasheet
<marcan>
yeah the datasheet link was correct
<marcan>
whitequark: somewhat worried about MIC5355-S4YMME not being in stock :/
<G33KatWork>
15 week lead time :/
<G33KatWork>
except if you buy a reel with 2500, then it's "only" 5
<marcan>
fwiw if we're in a bind, I think I can *probably* fit two discretes in there, instead of one dual regulator
<marcan>
that corner of the board has some space left
<marcan>
some jellybean part in a standard footprint would definitely solve the availability issue
<tnt>
marcan: if you git the same as the icebreaker I'm sure esden will be grateful, one less feeder to change :p
<whitequark>
that might not have enables
<tnt>
(they're just generic sot23-5 single ldo)
<marcan>
looks like that has two discretes
<marcan>
with enables
<whitequark>
ah
<tnt>
they do. he does power sequencing to follow the ice40 recommended sequence.
<whitequark>
ok
<marcan>
whitequark: I can rip this off of icebreaker wholesale if you approve
<marcan>
and I think i can fit it in
<davidc__>
looks like microchip is out of stock, with a ship date of Jul 15
<marcan>
the 1V2 testpoint might have to go
<whitequark>
marcan: let's do that
<whitequark>
hm
<marcan>
but then again we have testpoints on the bottom now, and the 3V3 and 5V ones might have to go to fit the LEDs
<marcan>
so whatever
<marcan>
I'll know when I try to lay it out
<whitequark>
we can remove the vrail testpoints from the front i think
<esden>
marcan: are you folks talking about the power supply? You are welcome to rip off the vregs off the icebreaker. Less changeover is always welcome :D
<whitequark>
it's mildly irritating
<marcan>
esden: yeah, part we're using is out of stock
<esden>
ugh ok... I got a few here for the prototypes but I arrow was running low on them IIRC
<davidc__>
the vrail testpoints could go anywhere on the front. No need to put em right by the regs
<whitequark>
discretes are prob safer long term
<whitequark>
i had some reservations about that uber specific part
<marcan>
davidc__: "anywhere on the front" is... really not that many places
<marcan>
especially not near those rails in general
<marcan>
whitequark: okay, I'll put it in the queue then
<marcan>
need to get some sleep now
<whitequark>
ack
<marcan>
we might want to wait a couple extra days before cutting C1, I'll try to get this in as soon as possible but I also need to work this week :p
<whitequark>
alright
<marcan>
any design constraints worth noting? current really, mainly
<marcan>
dunno how much draw we expect on 3V3 with the FX2
<whitequark>
mm i think the FX2 can draw up to 150 mA at most
<esden>
+1 for avoiding specific parts without multi vendor sources. Actually octopart is a good way to find out the availability of specific parts. :D
<marcan>
esden: I don't see any actual partno in the icebreaker schematic, do you have a datasheet?
<esden>
ohh sorry just a sec
<marcan>
and fwiw we went with a specific part for the ESD protection, but it has huge availability
<whitequark>
i mean we have a ton of specific parts
<marcan>
also the i2c pulls I think are a somewhat specific variant by NXP, but we really couldn't find any other viable options
<whitequark>
level shifters, ADCs, DACs
<esden>
SPX3819M5-L-1-2/TR and SPX3819M5-L-3-3/TR
<whitequark>
and that
<esden>
both are available from lcsc
<whitequark>
the only interchangeable parts i can think of are memories and LDOs
<G33KatWork>
lol, digikey doesn't have them in stock either :D
<davidc__>
FWIW, that regulator doesn't make any claims about stability with ceramic output capacitance
<marcan>
it's a generic footprint
<esden>
I was able to get most of the glasgow parts from lcsc... and most of the expensive parts from arrow, only very few I had to get from digikey I think.
<marcan>
should have tons of equivalents from various vendors
<davidc__>
so for that specific regulator, I'd want to make sure it is stable with low-ESR bulk capacitance
<G33KatWork>
oh, lcsc is the chinese thing. forgot about that
<G33KatWork>
any experience with them and the german customs office? :/
<esden>
G33KatWork: yes it is, and it is shockingly good...
<G33KatWork>
digikey is absolutely painless in that regard
<esden>
G33KatWork: nope ... german customs is always a pain in the butt... ship via DHL/FedEx to avoid trouble.
<electronic_eel>
G33KatWork: I had no problems with customs
<esden>
NEVER use "standard shipping"
<marcan>
only problem with the sot23 package is pretty shitty dissipation
<electronic_eel>
G33KatWork: I used the cheap shipping, was called 4px express or something like that
<marcan>
DFN-8 is another option with much better dissipation (exposed pad) at the cost of esden still having to change the feeders :p
<davidc__>
marcan: (see my note above about ceramic stability)
<marcan>
davidc__: yeah saw that
<esden>
marcan: I was thinking of switching over to DFN equivalents of the parts I listed.
<esden>
On all my designs, exactly because of dissipation issues.
<marcan>
ah, then if you're okay with it I can start with that
<esden>
so if you think this is an issue go ahead and switch to DFN versions.
<marcan>
and you can follow suit
<electronic_eel>
G33KatWork: got delivered like 2 weeks after ordering, by regular DHL (not express) and I didn't have to pay anything for customs even if it was about 100 EUR
<esden>
marcan: correct :)
<electronic_eel>
G33KatWork: I think it is not completely legal what the shipping company is doing there. They are importing it through Belgium according to the tracking
<esden>
marcan: when you are done poking around I should go over the schematic and add my inventory keys finally to the official repo. :) ... so I need to sit down and add all of them. (they key into my global part database and the PnP database... so I need them in there)
<marcan>
davidc__: this looks like something you can only really test and see, the datasheet makes no promises, right?
<marcan>
though at least if we go with a footprint with multiple vendors we can always swap it out for another part
<marcan>
esden: absolutely
<marcan>
off to sleep
<davidc__>
marcan: yes. Though typically LDOs will specify if they are ceramic-stable
<esden>
(did not have any issues with those SPX parts with ceramic output caps, on icebreaker nor black magic probe...)
<davidc__>
since its a selling point
<whitequark>
icebreaker and BMP don't stress the regulators as much, do they?
<whitequark>
3V3 one especially
<davidc__>
esden: yeah, not saying it is a problem; just saying that some LDOs can be unstable with ceramic caps.
<davidc__>
and its one of the things I always check in a datasheet before speccing one :)
<esden>
davidc__: is that not rather an issue with old LDO parts? Have not run into that issue yet. But there is always a first time for everything.