JACK

Hey there,

Quick update before leaving the office: I just added a nice LED connected to pin 32 and very neat logos on the top copper layer.

Of course the LED will be blue because blue is cool and there's the Skull n Wrenches logo because that's even cooler!

Every update on GitHub, photos updated here as well.

Cheers,

Mick

Hey there,

I finished the layout! I also updated the screenshots here in the gallery :)

I also revisioned the schematic so to remove any warning the ERC reported and added some copper pours on the PCB for power signals. Now I will just double check the PCB, to see if I could optimize the pours (I don't like empty board room).

As you can see there's some space left on the board, I may add an LED somewhere on the board (you know, for the classic Blinky test) and I will surely add a JACK logo somewhere. I could also do that on copper (!) because etched copper is way more precise than silkscreen, and looks neater!

After this last check, it's order time! .\m/

Cheers, Mick

PS: as always, check the Github page for the latest files.

Hey there,

After a week or so (read: after passing 10 minutes a day, for real) of work I managed to layout the most sensitive components of the circuit, that are in order of layout:

• the chip bypass caps (keep them as close as possible to the chip)
• the crystal (keep traces as close as possible to chip and of same length)
• the USB connector and transient suppressor (differential USB signal traces must be laid out as short and as equally long as possible, avoiding signal under them, some says they should also be laid at an angle to avoid some distortion on the signal due to patterns in the fabric of the FR4 ,but we're talking about USB Full Speed here, not USB3, so it's fine if you don't do that)
• the LDO and bulk bypass caps
• the power signals filters (USB shield filter to ground that also should act as "star ground", LC filters with ferrite beads to create clean analog and digital power signals)

I want to keep a 1 inch spacing between the two headers, but placing the USB connector centered on the left side of the board forced me to put the chip a bit off from the center of the board, which in turn led me to "push" the upper breakout header up of 0.1 inch (to leave room for the crystal). I'll fix this by moving the clock a bit to leave just the right space.

The tricky part now is mapping the pins in a convenient way, that is so to have the less distance between chip pin and header pin to ease the layout process; also, I need to take extra care of the analog power signals so to avoid any noise in them.

Hey there,

I just remembered that the JTAG header is still missing from the schematic; I will add it promptly. In the meantime, I'm proceeding with the layout of the board, it is going to be a bit though because I'd like to keep the Analog ground plane as separate as possible from the Digital ground plane so to have the best performance when using analog pins (which shall be connected to stuff powered from VDDANA and grounded to GNDANA), and also because using 0603 caps on such a small board makes it difficult to keep decoupling caps as near as possible to the chip while also not "walling" too many pins; I'll try to apply local ground planes under critical components (main chip, clock, analog stuff) and star them near the LDO.

As always, please check the repo for the most up-to-date version of the project files.

Cheers, Mick

Hey there, quick update before leaving the office:

I just finished polishing the schematic, I also added a nice hi-res picture of it both here and on github :)

Also, I started the PCB layout process; I still got to find (that is I still got to look for it) a decent and cheap miniature pushbutton for the reset circuitry; I'm also thinking that I might review the polarized cap packages, but then again tantalum caps might be perfect in the 0603 package so I'll leave them in that form for now.

Of course, every edit has been pushed on the Github repo.

Cheers, Mick

PS: thanks Atmel Corporation for skulling this project ;)

Hi there,

I just added a 24 MHz crystal that I searched for on Mouser, I now need to add programming/breakout headers and the schematic will be over... Woohoo!!

PS: I'm working on this project during my spare minutes at work... components sourcing 5 minutes a day is quite hard...

Cheers,

Mick

Hello there,

Quick update to let you know that I just updated the project components list to reflect the parts currently listed in the schematic. I got to find a decent 3.3 V LDO, decide whether or not to add some level converters for some digital-only pins, add programming/breakout headers and produce a few protos!

I'll keep you up to date ;)

Cheers,

Mick