ATMEL Mega1284P evaluation board avalible

I suppose I could have it do the routing with no hatching, strip out the grounds, clean up by hand, then let it try & put the hatching in again. Likely just leave me with unconnected grounds again.

Why are you hatching it then? Or just so it looks pretty...

Got it to work finally. Still had to make a few ground connections by hand, kinda like showing the program where to put a via or two so it could make the final connections. Moved a couple of caps slightly, moved a few traces so the ground planes could cover a little more area. Bit of an iterative process - tweak a trace or two, let the polygon refill. Move a part a scooch, let the polygon refill. Overall coverage between the 2 layers is good, got some voids in the bottom layer where the runs spanning long stretches don't give the polygon any access. Think I can add a via in the middle of the top layer and have it carry over to the bottom to get the voids filled?

Looking at parts for availability next - checking the SD socket to see if make can go in (digikey carries several, the mechanical drawings are not the easiest to interpret) or if the Sparkfun library part is unique.

When Eagle complains about "Clearance" errors around the regulator thermal pad, do I need to resolve that or can I ignore it as the top & bottom layers are intentionally connected together with vias?

I'm thinking this needs more work - looking closer, the top layer has a small pad in the middle that is isolated with an outer pad that is connectet to the ground hatching. The bottom pad is VCC, but is also connected to the bottom layer ground hatching. I need some way to isolate the regulator thermal pad.

if you shoot manually vias through you have to name each via according to the signal - in the thermal pad case "GND". You are missing the vias in thermal pad for the second voltage regulator.. The low profile crystal package fits under the chip.. Do use solid ground plane.. Generally : design rules - it depends on your pcb provider, most of them are checking them before the fab starts (and they shall provide you with their design rules definition, drill set definition etc..) and when they see an error they will not fab the pcb or they will charge additional fees.. :0 P.

Yeah, use a solid ground plane (or an almost solid ground plane if you absolutely have to stick silly hatching on it) and that routing's still ugly :D

What fab house are you thinking of using, go look if they provide design rules files - some do so you can easily check it yourself. ...and if the tracks are ground, you don't have to route them, rip them up and they will then just connect to the ground plane.

Ok, now that I've the hatched polygon figured out, I can try solid planes. I will check out naming the pads/vias as well. I had vias in both thermal pads, will check & see what happened to them. I might have just turned viewing them off when I did the screen captures.

There were a few pins that couldn't connect to the ground hatching because there were too many signal runs in the area. I had to run a trace by hand, adding vias to bring the signal under the part and back up to where there was a ground signal to hook up to. Just a little too complex for the autorouter.

I think part of the reason for the ugliness is the shield footprint. The placement of some signals is just poor, and the size of the 1284 means you can't cram everything all in the same spot.

Skyjumper just had some similar boards made (little bigger more connectors), the bare PCBs look good, I think I'll follow his lead as he's nearby (Boston area also) and they were made & returned pretty quick.

I think part of the reason for the ugliness is the shield footprint.

Nahh it's just the tracks going at funny angles.

Ah, the angles - thats all part of the shortest distance routing going on. The 40 pin DIP really stretches some of the signals out.

Hmm - I'd opt for a neat 45deg angle and a 1mm longer track any day but maybe that's just me

^^^ wot he sed ^^^

^^^ wot he sed ^^^

Iā€™d also opt for a few ms longer typing time and correct spelling and grammar any day :smiley:

to quote DEATH

"ho ho-ho"

While waiting for other boards to return from the fab, I give the ATMega1284P board a go. And here's the outcome!

I wanted the board to have minimal components and made the board as simple as possible. Some descriptions of the board:

  • Uses 6-pin FTDI cable
  • 5V/3.3V operating voltage selection through jumper
  • Optional 32.768 kHz
  • I2C pins location selectable to be either on analog pin row or on PORTC breakout header
  • Pin 13 LED driven through a MOSFET
  • Some small prototyping area
  • Same mounting holes position as Uno
  • Same ISP header location as Uno
  • JTAG header

I have thoughts of using a smaller output current 3.3V regulator but with very small quiescent current. This will allow for lower power usage and maybe use the 32.768 kHz in asynchronous mode during sleep. In this case, input voltage (battery maybe) is stuffed in from the 5V instead of the DC in. Comments and critics are welcome. No plans for fabrication on this board yet. :)

Nice expansion from a 328 to the 644/1284 family.

Nice-looking layout, not auto-routed I'm guessing.

I can't read the schematic, are you using an inductor on AVCC?



I think you can view the schematic on the image source link (Flickr) itself. Not too sure why the image was resized. It's manually routed totally. And yes, there's an inductor on the AVCC. :) strong feeling is the board needs an external RTC.. the idea running 1284p with the optional 32khz xtal @timer2 is nice, but when you start to work with it you will be soon unhappy not having the actual time ready anytime.. maybe to trade it for jtag and the prototyping area.. with a small dia coin cell it may fit, maybe..

Manual routing is the way to go - see how neat it looks all with nice 45deg angles :D

I'm doing the other one manually now, got about 10 signals to go. The ones that go from the top of the board down to the middle & bottom are a pain.

I'm doing the other one manually now

Heh, nice :)

You'll never go back to that evil autorouter!