May I ask why exactly this project is in the Timepieces section? Seems to me that's not really relevant. Nice project none the less.

Hi Dave,

Thank you for your question. I was not take a decision that this project landed in Timepieces. Thank you for appreciation.

Regards, Simon.

This is outside of your intentions/goals with these boards, I'm sure. But for what it's worth and concerning R'Pi's lack of ADC ports; I came across this: https://www.abelectronics.co.uk/p/72/Servo-PWM-Pi-Zero. It's a large board, taking up the entire connector strip on the R'Pi BUT it's actually just an I2C (3-wire) bus thing -- with opto-isolation thrown in. Such a chip (minus unnecessary opt-isolation) could be routed to the Arduino ADC pins, I suppose. But organising software support / user education on the R'Pi side would be a nuisance, I'm sure.

How many of analog pins would be required from your perspective?

What about resolution? 12-bit would be enough?

I have used and quite like the NXP GTL2003 level shifter chip ... http://nz.element14.com/nxp/gtl2003pw/ic-gtl-lo-volt-translator-20tssop/dp/2212068. You simply supply it with the voltage rails from each side. It's bi-directional and works great. Does not do analogue -- only digital logic. But that's fine in this case. Perhaps two of these would be enough?

I will use integrated circuit like you mentioned or something like this http://www.hobbytronics.co.uk/mosfet-voltage-level-converter

This depend how many space it will take (one site soldering concerning SMD - this is my target)

At this time in case of such a amount of components I would order soldered board at least with all SMD.

Simon, looking forward to receiving your Ardushield from IGG.

    This new project looks ambitious, good idea to have wi-fi, and Ardu-Pi connections on same board !!

Walt, thanks for comment, yes stil waiting for ArduSHIELD.

WiFi can help a lot build, test and run a project in the cloud. 

Here it will be the same things with logic converter for ESP8266, officialy they can work with max 3.6V, not officialy with 5V, but I'm not sure if this can last for long time.

http://hackaday.com/2016/07/28/ask-hackaday-is-the-esp8266-5v-tolerant/

I'm in on this from the IGG campaign for the ArduShield.  Great idea and worth having in my arsenal. The Pi version would be a good asset too but as stated by Bill with the logic levels and such.  i'm sure it can be overcome but at what cost and feature loss/gain?

Thank you for having be on https://igg.me/at/ArduSHIELD and support.

Yes, the logic level have to be translated. For sure space for Raspberry and correlated things have to be considered.

Any idea what kind of feature can be lost?

This is a good idea, although it won't allow every Arduino shield to run on the Pi. For one thing the Arduino has analog inputs that the Pi doesn't have. 

And then theres the issue of the Pi using 3.3 volt logic on its I/O pins, whereas most Arduino's use 5 volt logic levels.

But nonetheless this would be a handy board to have, best of luck with it and I look forward to seeing your progress.

Thank you for nice word.

You have a right, most Arduino shields run with 5V logic. 

I'm thinking that would be possible to change stabilizer on those boards from 5V to 3V3. Other case would be to implement bidirectional logic converter for each pin. 

Something like this: http://cdn.sparkfun.com/datasheets/BreakoutBoards/Logic_Level_Bidirectional.pdf

I encourage you to sign up on the www.AwesomePCB.com , when the PCB will be available I will let you know.

I'm sure you will opt for a chip, since it does 8 signals in a small package, rather than a bunch of discrete components and a MOSFET for each and every signal. Ouch.