ST Shield with small arduino-ish boards?

I have a few different types of AT-type processor boards (Arduino Micro, Trinket 5v, etc.) and am wondering which pins the ST shield rely on, and operating current/voltage required to use it with these smaller devices. Obviously, they are physically not the types to allow the ST shield to be piggy-backed onto them as does the Arduino Uno, so I am wondering what pins I have to connect to which ST Shield pins in order to make them talk correctly, and any other circuit requirements it has.

Thanks for helping the newbie out.

Pins 0-1 for rx/tx (or 2-3) there is a physical switch on Shield
Pin ~6
5 Volt and Ground

I believe the rest are pass-throughs to an Uno R3 layout


I was trying to figure this out today too – I’m wanting to hook it up to a Arduino Pro Mini 5V. I was concerned about using something with only a 5v regulator, since the Uno has 5v and 3.3v - as far as I can tell though, they only take the 5v, and regulate out their own 3.3v. I hadn’t noticed they were using pin 6 though - if you’re making your own connections to the pins, I wonder if it can be any PWM pin…

Watch out for anything based on the ATtiny85 though (digispark, Trinket 5v seems to be also?) - I’ve been trying to fit the SmartThings library into the 8kb they have, and the closest I’ve been able to get is 7.5kb with no sketch to speak of (which would be great, but the bootloaders take up 2kb). That’s just with the _isDebugEnabled stuff #ifdef’d out though, so someone with c++ knowledge might be able to get further. I’m guessing the SoftwareSerial library is taking up some space, and had wondered if using the hardware for serial would work instead, but I don’t think the digispark has RX/TX pins.

Micro it is!

btw - if SmartThings could offer another board that took power, ground, TX/RX and a PWM pin in the smallest form factor possible, that would be incredible. Then we wouldn’t be tied to the form factor of the (rather large) Uno R3, and it would open up a lot of exciting possibilities :slight_smile:

Agreed, that would be awesome!

Well… what is the shield? Isnt it just an built in xbee shield? With a couple other things added (RGB LED, couple buttons)?
Does the xbee have a custom firmware on it?
If this is the case, you could make a tiny smartthings “shield”

No, ST Arduino Shield does not use XBee module. Instead, it uses CEL MeshConnect with customized firmware.

MeshConnect Zigbee modules are similar to Digi’s XBee in architecture, but they are different products and are not interchangeable. The low-level interface to ST Zigbee module is not documented but can be inferred to some degree from their Arduino library source code.

Gotcha… well since ST is xBee compatible also, couldnt we use that with a HA stack?
I might just be assuming to many things here tho hahaha

I would also be super happy with just being able to buy the preloaded CEL modules, that’s really the only part I need. Releasing the custom firmware would also be wonderful, despite the fact that it looks like you need some specific equipment to program the modules.

I was hoping xBee modules would work as well - but there doesn’t seem to be an easy way to load them with the HA stack/profile. At least I’m having trouble finding it if there is…

Just thought I’d update on getting the shield to work with a smaller Arduino – here’s a picture of the setup I’ve got with my Pro Mini 5v in the breadboarding area.

It works great, just had to hook up the 2, 3, 6, 5v, and ground pins. I also removed the headers from the shield so that I could fit it inside a smaller area – here’s what the finished project ended up looking like (it’s a PillBug).

PillBug v2



That is really cool. Kind of hard to tell which device is the shield now. :slight_smile:

I wish there was all this “stuff” when I was learning electronics. I did have a “50 in 1” kit that had a transistor (one). Yeah, I’m old. They were barely past the tube age back then.

What are you going to build next?


Only one? Wow, thank goodness by the time I got one they were coming with a bunch, because I feel like I remember going through them pretty fast – wasn’t too clear on hooking them up correctly at first :slight_smile:

I’m probably going to try to add another set of mini blinds, I just got back a 3D printed servo horn that connects the servo directly to the blind rod, so less elastic bands :slight_smile:

BTW, does anyone know what pin 6 is actually used for? As far as I can tell, the shield still works fine without that pin connected. It doesn’t seem to be referenced anywhere in the SmartThings library either.

I asked about that pin and as best as I can tell, it does nothing now… but ST staff recommended leaving it alone so it’s available for future expansion. I’m not sure if the firmware on the shield can be updated remotely to make use of it in the future or what the deal is…

@dome that pin is connected directly to the radio, but doesn’t have a use right now.