#timvideos

Hello

hi

Hi Carl

im new here

hello - what brings you here ?

im an electronics engineer.. looking for pcb design work..

what about you?

@mithro suggested some projects to work on

I'm mostly into software and going to events to record talks

and running down the street to get a pizza. brb

cool. Nice to meet you

aravind_: I'll be around in a couple of hours

Currently out at brunch

Sure no prob.. i will be here till my blankets pull me in

:)

If you are still around then, we can chat about possible projects

I'll also respond to your email

Great :)

tumbleweed / CarlFK: the vizzini driver should be replaced with the stuff Ben (The debian dvswitch guy?) and shenki working on

mithro: it may have happened, but now it needs to trickle down into the distros.. and the odroid is pretty far behind - like on kernel 3.14

CarlFK: I'm 100% sure it hasn't happened

I stopped bugging shenki long enough he has probably forgotten all about it

aravind_: I'll be around in about 10-15 minutes, you still awake?

Sure @mithro

Great, talk to you then

aravind_: couple of questions while I walk

sure

aravind_: what OS do you generally use?

aravind_: Have you used KiCad before?

mithro i use OS X

yes I have used KiCad before

What is your level of experience in this area?

circuit design --> been in industry for last 10 years

What are you hoping to get out of this? Practice? Something for your portfolio? See something you created be used? Cool friends to hang out with? Want to give back to the community?

Need something interesting to do in your spare time?

Well all of it + i plan to start design services , a small step to be my own boss :)

Ah cool!

:)

as of now, my plan is to work when I get spare time (few hours a week)

So, I guess your more looking to come up with a good workflow where you can do designs quickly and efficiently?

KiCad is probably the least tested on Mac, but at least you have things like proper scripting environment

I have used KiCad for some designs in my mac (not very complex though)

Almost at a computer now

okie dokie

On the experience side, do you know about things like differential traces, length matching and impedance matching (even if you have not done them in KiCad)?

Btw what have you used professionally? Altium

?

yes

professionaly mostly PADS and CR2000

i was a circuit designer mostly , layout being done by layout engineer.

Finally at a computer now! :)

Typing is much easier than doing it on the phone while walking ;)

CarlFK: ping? You still around?

mithro: here

i concur :)

aravind_: so, are you just interested in the PCB side of things, or want to do the full circuit design too?

happy to be on full circuit design

spec + schematics + layout + sims

aravind_: okay cool

@mithro I understand your projects are version controlled using git

aravind_: as I mentioned, the two projects that I think would be good to start with are, the TOFE-VGA board and the TOFE-HiLink board

Okay.

@mithro I will go through them in detail. Anyone else working on those at the moment?

aravind_: the TOFE-VGA was being worked on by seaLne - but he ran into issues with RSI, so had to stop

I believe it was at the stage of the schematic being pretty much done and he was starting the PCB layout / design

@mithro any detailed doc for the proj?

aravind_: Sure, let me give you a bit of background

@mithro Thanks

aravind_: The HDMI2USB project originally started using the Digilent Atlys boards for developing our firmware

aravind_: The problem is that the Digilent Atlys boards don't have any VGA capability and VGA is probably going to be around until the heat death of the universe

:)

thats true, people still use VGA for something or other

aravind_: The Atlys boards have an expansion connected - it looks like the old SCSI ones and is called the VHDCI (Very High Density Connector Interface)

okay

aravind_: so, in 2014 we had a Google Summer of Code student develop an expansion board which connects to the VHDCI interface and allows VGA capture

okay

This board works okay and there are about 20-30 floating around the world

aravind_: You can find that board design at https://github.com/timvideos/HDMI2USB-vmodvga

Title: GitHub - timvideos/HDMI2USB-vmodvga: VGA capture expansion board for HDMI2USB (or Digilent Atlys prototype board). (at github.com)

aravind_: with a bunch of description from Rohit

okay

still getting my grip around git :)

aravind_: GitHub has quite a lot of good documentation about using Git+GitHub on Mac

aravind_: They have a bunch of tools which are Mac only but have nice UI and stuff

aravind_: I have been using git for 5 years. I know about 1%: I commit, I push, and sometimes I clone to some other box.

that's all you really "need" to know to get going.

@mithro you are right :). I am following the tutorial now

aravind_: The Atlys board however is a development board, which isn't really all that suitable for what we want to do - which is record conferences

okay

got it

aravind_: so we created our own board which is pretty similar called the Numato Opsis

so a dedicated board is needed

aravind_: the VHDCI connector however is super expensive - like $4 to $8 each

aravind_: so we didn't use it on the Opsis

yes i think its a dense connector for I/O expansion

aravind_: instead we decided to reuse PCI-Express connectors instead - which means that the expansion boards don't even need a connector

ah okay

aravind_: The usage of PCI-Express connectors in this manner is a "open standard" I'm trying to promote which is called TOFE (Tim's Open FPGA Expansion)

got it

@mithro so the PCIe pinouts dont match to the standard

aravind_: I've tried to keep it as close to PCI-Express as possible, we just allow the signals to be slower than PCI-Express uses

okay. whats the max signal rate in our case?

aravind_: All the power pins and data pins are in the same locations, so you can plug in a PCI-Express card and it won't blow up

ah okay

aravind_: I'm trying to do as minimal amount of work as possible ;)

I understand :)

aravind_: The signal speeds are DC -> ~1.5Gbit/s

aravind_: PCI-Express starts at about 1.5Gbit/s and goes up to 16Gbit/s (possible 32Gbit/s?)

is this per lane speed? or overall?

aravind_: per lane

okay cool

any post layout sims? to check sig integrity?

aravind_: So, at 1.5Gbit/s we do care about things like impedance matching and differential traces, etc

aravind_: Nope, we just kind of pray and hope most of the time :P

hows the board stackup done?

ha ha

aravind_: We have two existing TOFE boards - the "LowSpeedIO" and the "Milkymist Compat" boards - both operate in the 100kbit/s to 1Megabit/s type range where it doesn't really matter

okay understood

aravind_: another cool advantage of being mostly compatible with the PCI-Express standard is that we can buy adapters and stuff intended for usage inside a computer and use them

yes

who will be end users?

aravind_: Things like this -> https://www.amazon.com/gp/product/B00KZIAHW8/re... and https://www.amazon.com/Tenext-Express-Adapter-F...

me :)

aravind_: so to finally get to the point

CarlFK :)

okay

aravind_: the TOFE-VGA board takes the design used on the vmodvga and changes it to instead fit the TOFE connector + form factor

okay

mech specs are defined?

aravind_: yeah - PCI-Express + a couple of extra mounting holes

great

I saw in your google drive that these boards are manufactured with 2 vendors

aravind_: I've also been trying to build up things like templates

Any specific rules from them?

aravind_: so it is easy for people to create new TOFE boards and such

ah great

aravind_: The aim would be that boards we create should be producible by both hackvana and ohs park

okay

aravind_: neither do controlled impedance stuff

oh :(

aravind_: so again we just do our best

then we should really pray

:)

aravind_: The apertus/AXIOM guys (see Bertl_zZ and se6astian|away) have gotten okay results with OHS Park using the rules I put in that document

okay. I will follow the same rules

aravind_: yeah