mcu keychain

[robust raft]

Could someone look over this its verry small and not much on it so it should be fast ;)_ _

[nimble island]

why two decoupling caps on an attiny

[pine zephyr]

you should put tvs on the usb

[robust raft]

I should have had one but idk

[robust raft]

I really should xd

[robust raft]

iss it bad tho?

[nimble island]

just adds an extra part for no benefit

[robust raft]

@nimble island Did I now make you both happy? ;)_ _

upsie

[nimble island]

🤔

theres still no tvs lol

[robust raft]

there is its wired wrongly tho xD

[pine zephyr]

you should use a tvs diode that's designed for usb

[robust raft]

do you mean for the datalines?

@nimble island Tvs like esd for the datalines or?

[nimble island]

ya

[robust raft]

I thought for the vbus xD

[nimble island]

power is less critical, you're already using an LDO which is probably fine

throw on a zener if you're worried about it

[robust raft]

I will if your worried about that xD

[nimble island]

meh

apparently there are chips that do ESD protection for the entire thing

vbus, D+ and D-

nice neat little packages

[robust raft]

yeah found one

[robust raft]

now I got it what do you think?

[nimble island]

y d1

[robust raft]

sorry forgot it now?

[nimble island]

idk if its discord or low resolution

[nimble island]

not necessary to slice your ground plane under everything for 3v3

[robust raft]

well I didnt it was kicad xD

[nimble island]

the big blue trace

uh

drc isnt set up correctly?

or you have a bunch of violations idk

[robust raft]

Nope gnd pour

[nimble island]

route it out of the way lol

[robust raft]

I don't I hope

[nimble island]

i just ran drc

you have over 100 violations its not set up correctly 👀

[robust raft]

🥲

[robust raft]

Why tho it's an ldo or because of the pour?

[nimble island]

its running to a decoupling cap, the extra inductance is probably fine and it means you keep a mostly solid pour underneath your chip and most of your traces

[robust raft]

The only other way would be for it to go around the headers

[nimble island]

so?

[robust raft]

Well should I avoid trace contact in general or only cap contact because of the inductans

Inductance

[nimble island]

the inductance is going to be largely nbd

[robust raft]

Not be determined because it's so small?

[nimble island]

no big deal

yes

[robust raft]

Then why should I move it in the first place I mean I will but idk

🤔

[nimble island]

think about the returns

[robust raft]

Would be bad if your had flows and return at the same time?

[nimble island]

wym

current necessarily flows in a loop

[robust raft]

Yeah but what is so bad about this line?

[nimble island]

Your returns will all need to flow around that split

whereas the other way only has power flowing around

[robust raft]

If I move it don't they still have to flow around it? Or do you not mean the distance between the line and the copper Pour?

[nimble island]

no

if you move it back on top ASAP you'll keep the split small

[robust raft]

Oh yeah but how?

[nimble island]

route straight down under PA4 and via back up

nudge j2 right if necessary

[robust raft]

Okay well I'll try

[nimble island]

@robust raft https://embeetle.com/#blog/return-currents

notice point 2 specifically

[robust raft]

I think I get it you don't want me to route on the bottom layer all the time only if I really have to because the return current needs to take a long way

[nimble island]

importantly that the high speed trace return currents need to go around the split

[robust raft]

And that's bad isn't it?

Because it's a big way around it?

[nimble island]

honestly

for this design, it probably does not matter at all

but its a good time to practice now while the stakes are basically zero

to answer your question, yes

[robust raft]

Yeah it is

[robust raft]

Did you see Maddie's design? She really did go on 2 layers to route it all I mean she layer switched often

And Daniel mentioned to put gnd vias on these spots (next to)

[nimble island]

that design uses more than 2 layers 👀

[robust raft]

I know we don't have a high speed signal but could I also do this here?

[robust raft]

Yeah but the signals are routed there

And 2 gnd layers in

Xd

[nimble island]

yeah you can throw return vias where they fit

[robust raft]

And that would smaller the split wouldn't it?

[nimble island]

sorta

it does that in the 3rd dimension ig

[robust raft]

But it would work hopefully

[robust raft]

@nimble island What do you think? :)_ _

[nimble island]

Remind me in an hour

[robust raft]

Sorry Chris I slept and I’m in school now xd

[nimble island]

No worries

[robust raft]

Good morning chris xD

[nimble island]

Morning

[robust raft]

Good sleep?

[nimble island]

Never 😆

[robust raft]

damn so you have school today? xD

[nimble island]

Yeh

[robust raft]

have fun :)_ _

and I reminded you in 16 hours xD

[nimble island]

Im already done lol

[robust raft]

so no school? 🥲

[nimble island]

I had all my classes already

[robust raft]

damn your fast chris

[robust raft]

so watcha doing now chris?

[robust raft]

so chris :)_ _

[nimble island]

3d printing

i can take a look at your design

@robust raft pls run DRC before review

[robust raft]

yooo sounds fun

Now I wanna know

[robust raft]

here you chris sorry I didnt know that it had problems tbf

[nimble island]

theres still a bunch of clearance problems

[robust raft]

no?

This is just the silkscreen stuff and so on

because the usbb overlapps over the edge cuts

does the clearence and so on not go with the pcb file or is something wrong?

[nimble island]

you have clearances of like 0.1mm

[robust raft]

yeah is that bad? I mean I needed that to route out the attiny

[nimble island]

yes

its not manufacturable

try to keep clearances at least above 0.12, ideally around 0.16-0.2

[robust raft]

its not??

[robust raft]

I thought it was wth are you sure you arent confusing inches and mm or mils?

[knotty bluff]

where are you getting the board manufactured and how many layers?

[robust raft]

2 jlcpcb

hhm chris seems right

[knotty bluff]

outer layer should be 1oz though, unless you order 2oz

[robust raft]

nah its 1oz

so yeah

[knotty bluff]

2 layer 1oz gets you 0.1mm clearances

better to be above that whenever possible though

[robust raft]

yeah true

[robust raft]

I ofc directly jumped into kicad to fix this and now my clearance is 0,12mm ;)_ _ even tho 0,1mm is manufacturable its always good to be above 0,16mm wasnt that possible

[nimble island]

0.1 mm is not readily manufacturable

its right at the edge of jlc's 2 layer capability

Min. track width and spacing (1 oz)

0.10 / 0.10 mm (4 / 4 mil)

honestly this project is doable entirely with 0.2mm trace space

[robust raft]

🤔 you k ow what just because you want to I will deliver

Know

[nimble island]

the space between the pads of the ch340x will be under 0.2mm but thats okay

[nimble island]

I noticed you used thicker traces for some of the power lines, they may* need to neck down for some of the finer pitch ICs

[robust raft]

yeah I noticed thats what I wanted to ask you about because the atiny has verry small pads

[nimble island]

also

10u 0402?

(you cant route under an 0402 reliably either 😉

[robust raft]

https://jlcpcb.com/partdetail/16204-CL05A106MQ5NUNC/C15525

yeah seems to be avaliable

[robust raft]

😔

[nimble island]

just rotate C1

C3 has space to move up a bit

[robust raft]

does it need to tho?

[robust raft]

what would that change?

[nimble island]

yeah its way too close to your other traces

[nimble island]

you're routing underneath it rn

[robust raft]

not anymore ;)_ _

[robust raft]

the tx and rx i suppose

[robust raft]

chris what do you think now? you will see the things you mentioned in the drc

[nimble island]

lgtm

1mm headers be expensive tho

actually theyre not so bad for a single row

[robust raft]

well its okay I think because I dont use many

[robust raft]

So everything should now be alright 😁

[nimble island]

yeh

[robust raft]

Nice 🙂 what are you up to?

[nimble island]

procrastinating atm apparently 😂

[robust raft]

That sand xd

Bad

Xd

[robust raft]

@nimble island look what came yesterday :)_ _

its really smol xD

Problem now only is its getting recognised in the device manager but I dont see any output in putty

[robust raft]

@tawny otter What do you think :D_ _

[robust raft]

@nimble island about that it doesn't work I think 🤔

[nimble island]

do you have any software flashed on it?

[robust raft]

Nope but shouldn't there be something already on it?

[nimble island]

no why would there be

[robust raft]

Not like anything in the uart output?

[nimble island]

no

it will be filled with noop or something

[robust raft]

It's now filled with nothing lol

[nimble island]

yes

the flash will be noop

you could bridge tx and rx on the ch340 to get an echo without programming it if you just want to test that part

[robust raft]

well the ch340 works because it show up in windwos :D_ _

[weary vale]

@nimble island - doesn't look like it needs to be double sided assembly! 😂

[nimble island]

no

[raw pike]

damn nice

[robust raft]

Yeah it was just a general question xd

[torpid wraith]

nice

write the firmware in hex

[robust raft]

I don't even know how to write the firmware xd

[torpid wraith]

problem for later 😛

[robust raft]

Problem is it's now later xd

[robust raft]

Here @torpid wraith

[torpid wraith]

yeah, saw that

wait, why are there two holes

[robust raft]

I hate firmware 😔

[nimble island]

do you have a rpi or arduino

[robust raft]

Yeah both

[torpid wraith]

just leave some software out to harden in the sun

[nimble island]

you can probably use either to program it

[robust raft]

If you want the USB port up or down :)_ _

[torpid wraith]

which mcu is it

[torpid wraith]

ok

[robust raft]

Should work hopefully xd

[robust raft]

Attiny 1616 I think

[robust raft]

Why not just use my PC?

[nimble island]

how are you going to connect your PC to this

[torpid wraith]

if it doesn't have the arduino bootloader on it (for UART programming), you need an icsp programmer

but arduinoISP exists

so you can just use your arduino

[robust raft]

As Chris said it doesn't have anything on it atleast that's what I see in putty

[torpid wraith]

there's probably something similar for a raspi

[torpid wraith]

yeah, but you can program a blank chip with an icsp programmer

even if it doesn't have the bootloader on it

[robust raft]

How do I do that? I don't think I routed them out directly. But I think I can just use some gpio pins can I?

I will just Google this tbh

[torpid wraith]

no, they have to be the specific gpios

should've planned in advance

worst case is you need some bodge wires to connect to the icsp pins

[robust raft]

Should have xd didn't think I can't program it through is p I thought I could just use the uart but sadly not 😔

[weary vale]

.....:awkwardmonkey.gif:

[weary vale]

that's the one 😂

[tawny otter]

You can only program an MCU through UART if it already has a UART capable bootloader on it. A blank MCU needs the native programming pins exposed

[robust raft]

yeah idk why but I thoughtr it was already on it xD

[nimble island]

@robust raft you'll need to bodge a wire to reset pin

[robust raft]

to the reset pin?

[nimble island]

Yeh

[tawny otter]

Used for programming