P2 Eagle

JohnC

Is there a known-good Eagle footprint for the P2 yet? Search is foggy.

Rayman

I've posted the Eagle files for my P2 board here:
https://forums.parallax.com/discussion/170725/my-first-p2-pcb-its-alive/p1

P2 footprint works. I've fixed some pullups and other things there, but haven't tested the revised layout yet...

ManAtWork

Yes. I have a rather old version of Eagle so I've attached it as script. I think this could be imported to any version by executing the script.

JohnC

Thanks, gentlemen.

JohnC

@Rayman do you know the rough one-off BOM price for everything on that board?

Rayman

I don't have a complete list, but I just pulled up my Digikey order of special parts I needed for this board and made the attached semi-BOM.

Note the suggested changes for better RTC and crystal for RTC.

Rayman

Also, there are some changes to the power supply circuit I may or may not make in the future...

I could use the LDO 3.3V output for any special pins that need a quite supply. So far haven't needed that.
I may also send a P2 I/O pin over to an LDO enable so that I can unpower/power things like USB, uSD for cases where they get non-responsive and need power cycling...

Also, may look at doing something different with the reset input to the power regulator...

Rayman

Also, I noticed my P2 chip gets very slightly warmer than that on the P2 Eval board...

Maybe adding more vias would change that, but really it's very slight and so far hasn't been an issue even at 297 MHz...

Rayman

Just wanted to mention (in case you were going to use more of that design).
I think there's an issue with the micro-usb connector.
Seems I'm getting an overlap error on this part.
Thought I imported a good footprint, but guess not...

Update: Ok, the library part is OK. Problem is with the "restring" parameters in my design rules.
I guess I'm using the design rules from Sparkfun.
But, the minimum pad size settings were telling Eagle to make the pads bigger than they are in the library.
All better now...

JohnC

@Rayman, did you ever receive these boards from a few weeks ago and test them with all the rev2 changes?

Rayman

I was putting one together when got sent home...
Seems it's not so essential...

I was having trouble with the power supply chip... My solder paste was too thick and it shorted out underneath...
I tried several times to get it with air gun, but no luck yet...

I'm going to sneak in sometime soon and retrieve it though and try again

Rayman

I did decide I should have solder jumpers there to isolate the power supply so I can separate the supply from the load for seeing what's wrong...

I think somebody with better equipment wouldn't have so much trouble.

I am questioning the use of the QFN power supply chip. May have been beyond my abilities a bit...

JohnC

QFNs by hand are mean. That is all.

Rayman

I finally went back to work and tried to fix the QFN power supply chip last week...
Played around for more than an hour and couldn't make it work...

The funny thing was that it did work when given power via the DC jack. The 3.3 and 1.8 V powers were good, but it wasn't taking over serial...

Today, I just realized the whole problem may be that I forgot that I need to use FTProg utility to configure the FT231x!
Hopefully, doing that will make it work and I can declare the board design good.

But, I'm getting new boards with the power supply simplified to linear regulators (with option to use 3-pin DC-DC converter modules instead if need to be more efficient).
At this point, easy assembly is more important to me that efficiency...