rickman  wrote:
> I would be writing my own programs using Gforth.  It would be talking to
> external devices and, as I've said, using the phone for the UI.  The phone
> will do data collection, status display and perform whatever calculations
> are needed to support that.  It might also do data logging.  Nothing
> complex so not demanding of the software on the phone.  I'm thinking for
> $50 it is cheaper than a tablet or a pi with attached display and keypad
> and a *lot* more flexible.

Surprisingly, there does appear to be gforth for Android:
https://wiki.forth-ev.de/doku.php/en:projects:gforth-android:start

However I'm not sure how well it will play with the phone UI - does it use
the Android widgets or do you have to build all of that yourself?

Otherwise I'd suggest implementing your control logic on, say, a Pi and
having the tablet talk to it via wifi - simplest would be a web interface.
Any tablet you buy will have a web browser so you can treat them as
completely interchangeable.  The Pi running the control logic and web server
is where the application does most of its work and talks to whatever
hardware you need.

You might get away with a more basic microcontroller instead of a Pi, but
running a wifi/TLS/etc stack on those is a bit of a pain.  Maybe an ESP8266
would suffice, but it's quite limited especially when doing TLS.

You could go Bluetooth or USB device instead, but the downside is there's
more risk it will be incompatible with future tablets in some way.

Theo

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