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Using Arduino => General Electronics => Topic started by: sylvain_van_iniitu on Apr 14, 2018, 08:41 am

Title: Mega and standard PCB
Post by: sylvain_van_iniitu on Apr 14, 2018, 08:41 am
Hello !
i wanted to use a standard PCB on top of a Mega using simple male headers, but realized that the pins 8 to 13, GND and AREF did not follow the spacing of the other headers.

any workaround to this problem ?

what i've been thinking so far :
- unsoldering header 8 to 13 and AREF and wiring those to the PCB
- buying another mega with loose headers ( here (https://alexnld.com/product/geekcreit-mega-2560-r3-atmega2560-16au-development-board-without-usb-cable-unsolder-pin-header-for-arduino/) )
- trying out some other mega with a different disposition of pins, PCB compatible ( here (https://alexnld.com/product/arduino-mega-2560-atmega2560-16au-compatible-with-mwc-pirate-control-board/)  or here (https://www.ebay.com/itm/Mega2560-CORE-smart-mini-2560-ATMega2560-Arduino-Compatible-/221502571388) with this very elegant substitute to my main PCB : here (https://www.ebay.com/itm/221938290254) )
- adding a prototyping shield for mega ( but then i lose all interest of directly putting the mega into the main PCB ) ( here (https://store.arduino.cc/arduino-mega-proto-shield-rev3-pcb) )

any other ideas ?

and also, is there any good reason to this strange spacing ?

Sylvain

Title: Re: Mega and standard PCB
Post by: pert on Apr 14, 2018, 08:55 am
The curse of the Arduino offset header! You will encounter the same thing on the boards with the Uno style form factor too (Leonardo, Due, Zero). Luckily there are some sane boards like the Nano, Pro Mini, Pro Micro, MKR boards, etc.

any workaround to this problem ?
One possible solution is to simply not use the pins on the offset header. You have so many pins on the Mega so there's a good chance you don't need those. That's more difficult with the Uno-style boards since they have less pins.

There's some trick with bending the male header pins so that the will offset the screwyness. Someone was selling those for a while but I don't remember who it was.

- trying out some other mega with a different disposition of pins, PCB compatible ( here (https://alexnld.com/product/arduino-mega-2560-atmega2560-16au-compatible-with-mwc-pirate-control-board/)  or here (https://www.ebay.com/itm/Mega2560-CORE-smart-mini-2560-ATMega2560-Arduino-Compatible-/221502571388) with this very elegant substitute to my main PCB : here (https://www.ebay.com/itm/221938290254) )
I think that's a good solution.

and also, is there any good reason to this strange spacing ?
Arduino made a newb screwup many years ago and instead of just eating the loss and fixing their mistake, as any responsible business would have done, they unleashed this curse on the entire world and now that idiotic offset header format has leached its way into so many products. See:
http://forum.arduino.cc/index.php?topic=22737.msg171839#msg171839 (http://forum.arduino.cc/index.php?topic=22737.msg171839#msg171839)
Title: Re: Mega and standard PCB
Post by: MorganS on Apr 14, 2018, 06:28 pm
Learn to use Eagle or KiCad and design your own PCBs. The quality of board you get for $5 is incredible these days.
Title: Re: Mega and standard PCB
Post by: sylvain_van_iniitu on Apr 14, 2018, 07:54 pm
Learn to use Eagle or KiCad
thanks for the tip!   might indeed be a good idea.   until now i only briefly considered using the PCB proposed by Fritzing, but never did.    will look what Eagle might propose
Title: Re: Mega and standard PCB
Post by: CrossRoads on Apr 14, 2018, 09:19 pm
Try another form factor, like a Mega2560 "system on a chip"
(http://www.crossroadsfencing.com/BobuinoRev17/2560%20assembled%20front.jpg)
(http://www.crossroadsfencing.com/BobuinoRev17/2560%20assembled%20back.jpg)

Or in DIP form factor
(http://www.crossroadsfencing.com/BobuinoRev17/MegaDipBreadboard.jpg)
(http://www.crossroadsfencing.com/BobuinoRev17/TopPic.jpg)
(http://www.crossroadsfencing.com/BobuinoRev17/BottomPic.jpg)

Title: Re: Mega and standard PCB
Post by: hammy on Apr 14, 2018, 10:21 pm
You can get breakout prototype shields for the mega , build your circuit on one of those ?

Or ...

As suggested a board on one half of the mega , with flying leads , if needed to any pins on the other half ?