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Shield Compatibility between models

Sat Sep 19, 2015 2:27 pm

I thought it might be useful to community members if a line item were added to the Wikipedia specs to document details so that one can determine if a shield from another model will work on another (perhaps this is not possible). ... ifications

I started by copying the a line item entry to the bottom, but it's the final weekend of summer and Central Park is calling, so I hope that this start will encourage others to update the line item. Cheers!

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Re: Shield Compatibility between models

Sun Sep 20, 2015 1:27 pm

Theres essentially 3 generations of GPIO arrangements on raspberry Pis. There is also the compute module which has totally different external connectivity arrangements from any of the regular Pi models.

Raspberry Pi model B rev 1.x . This only had the 26 pin main connector, it also had no mounting holes.
Raspberry Pi model A/B rev 2.x. This added a second IO connector (not populated by default) with some extra IO on it. Most notablly I2S. It also added mounting holes and It also swapped the I2C busses which will require software changes for any expansion boards that use those pins.
Raspberry Pi model B+, Raspberry Pi model A+ and Raspberry Pi 2 model A. These got rid of the secondary connector and extended the main connector. They also changed the location of the main connector slightly.

Expansion boards deisgned for the original Raspberry Pi model A/B and using only the main connector will normally work on all Pi models (software support permitting) but they will sit in an offset position when placed on a B+/A+/Pi2. Some boards may also need an additional stacking header to avoid collisions with components on those boards. Boards connecting with a ribbon cable will also need either a special cable or a stacking header to use them on the B+/A+/Pi2 as otherwise the edges of the ribbon cable connector will collide with the extra pins.

Boards that use the extra connector on the Raspberry Pi model A/B rev 2.x cannot easilly be connected to a B+/A+/Pi2 (it's sometimes possible with software changes and a load of individual jumper wires).

A+/B+/2B expansion boards are likely to have connetors that will not physically fit on a Raspberry Pi model A/B without using a stacking connector to space them off the board. They may also be reliant on the additional IO lines that are not present on a Raspberry Pi model A/B

Not sure if this fits nearly in a table or is better described in prose. It's probablly not suitable for wikipedia in the form i've written it above.

P.S. please don't add confusing placeholders to wikipedia articles.
P.P.S shield is a term from the arduino community

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Re: Shield Compatibility between models

Sun Sep 20, 2015 2:02 pm

R1 to R2 also changed some of the GPIOs

Pin 3 changed from GPIO 0 to 2
Pin 5 changed from GPIO 1 to 3
Pin 13 changed from GPIO 21 to 27

Weren't some more of the 'ground' pins connected as well ?
Last edited by gordon77 on Mon Sep 21, 2015 8:51 am, edited 1 time in total.

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Re: Shield Compatibility between models

Sun Sep 20, 2015 2:55 pm

gordon77 wrote:Weren't some more of the 'ground' pins connected as well ?
No, they were always connected. They were just made "official" in the Rev 2.0, along with the 3v3 pin 17. Previously they had been designated "DNC", just in case of design changes.

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Re: Shield Compatibility between models

Sun Sep 20, 2015 11:16 pm

Nice work. This community is truly special :)

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