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feedback on protomega

Posted: Tue Nov 13, 2012 3:26 am
by effgee
Hi

no dedicated forum for the proto shields, I thought this was the closest. Please move if required.

+ love that it fits within the shadow of the ether mega
+ love the fact it doesn't foul the ethernet port
- would have preferred if (no sniggering now) long-legged female headers were provided, so I could stack another shield on top
- not keen having the ICSP port plonked in the middle of the board - it seems more likely to have it get in the way of other components.
- the ICSP port is 'partly shaded' by placing another shield on top.
? (pedant warning) why do pins D0, D8, D21, D36, D37, D53, D53, A8 & A0 have square solder pads ? Doesn't that normally signify an anode ?

Re: feedback on protomega

Posted: Tue Nov 13, 2012 5:51 am
by cef
effgee wrote: - not keen having the ICSP port plonked in the middle of the board - it seems more likely to have it get in the way of other components.
They're advisory use only (ie: not connected to anything, like the holes around it, and can be used for non-ICSP uses). They line up with the ICSP pins underneath. You'd have to put a female header that sits on the ICSP header to expose them.
effgee wrote: - the ICSP port is 'partly shaded' by placing another shield on top.
Part of the idea is that you can "if you wish" load a female header on the board and access the pins either using an ICSP, or perhaps build yourself an ICSP shield.

There's no spec that you need to leave that section of a shield free for the ICSP header at all. The proto board provides the pins as a convenience so "if you prefer" you don't need to remove it.
effgee wrote: ? (pedant warning) why do pins D0, D8, D21, D36, D37, D53, D53, A8 & A0 have square solder pads ? Doesn't that normally signify an anode ?
Usually it also indicates pin 1 of a connector. My guess would be that the board design uses a bunch of 6x1, 8x1 and 2x1 pin connector layouts to produce the desired layout. This was most likely done as I doubt the whole Arduino Mega layout existed as one set of 'pins' in Eagle, that could be just dropped on the board (or whoever made the "Mega" layout created it from other pin header layouts assembled as a 'group'.

eg: D0-7 (8 pins), D8-13+Gnd/AREF (8 pins), D14-21 (8 pins), A0-7 (8 pins), A8-15 (8 pins), and Reset-VIN (6 pins). The large 36 pin connector is most likely done as +5V (2 pins), Gnd (2 pins), D22-36 (evens - 8 pins), D23-37 (odds - 8 pins), D38-D52 (evens - 8 pins), D39-53 (odds - 8 pins).

Re: feedback on protomega

Posted: Tue Nov 13, 2012 10:46 am
by effgee
Thanks for the reply.
cef wrote: They're advisory use only (ie: not connected to anything
Thanks for the clarification. Guess I should have checked the schematic first.
cef wrote: Usually it also indicates pin 1 of a connector.
Thanks - I kind of suspected that, but was a little confused by D36 & D37. Still am. The Eagle/grouping explanation makes some sense, it was more curiosity to increase my understanding.

Re: feedback on protomega

Posted: Tue Nov 13, 2012 9:06 pm
by cef
Sure Jon (who designed the board) will pipe up at some point when he's not flat out. ;)

Re: feedback on protomega

Posted: Tue Nov 13, 2012 9:59 pm
by effgee
cef wrote:when he's not flat out. ;)
like sometime 2027, when he's retired ;P

You've pretty well got it covered, thanks cef. I'm sure Jon's got far more important things to do.

Re: feedback on protomega

Posted: Thu Nov 15, 2012 3:48 am
by effgee
Nooooo!

I just realised the inset duplicate IO pins along the long sides of the board don't line up with anything. They're not a multiple of 0.1" from anything, foiling my cunning plan to straddle connectors http://littlebirdelectronics.com/produc ... mount-6pin for access to IO pins without soldering fiddly jumper wires.

Would love to see this fixed in a future version - i.e. moved inboard to line up with the 0.1" main grid, i.e. D14-D21 (duplicates) move to line up with D24/D25, & A8-A15 (duplicates) to line up with D52/D53.

Hope they didn't make too many v1.0's & this can be improved for v1.1 :(

Re: feedback on protomega

Posted: Thu Nov 15, 2012 7:00 am
by effgee
cef wrote:Usually it also indicates pin 1 of a connector.
Now I've noticed that Pololu use it to indicate GND. Go figure.
I guess it means "there's something different about this one", i.e. there is no accepted standard.