Multiple (Simultaneous) Sensors

John Riggles

So, I'm not certain if there's already out-of-the-box support for this, but I was wondering if Twine is capable of interfacing with multiple external sensors at once. I.e., say I'd like to connect the Breakout Board and Moisture Sensor to the same Twine. Is that currently feasible, or (if not) does Supermechanical have any plans for some sort of 'Sensor Hub'?

Grant Hulbert

I was disappointed to discover that twine does not support multiple sensors out of the box...I paid for it in advance on the (very reasonable) assumption that all sensors could be used at once. Why else would I have bought the sensor 3-pak, if I didn't intend to use all the sensors?

Tucker Hottes

@Grant Hulbert, I was also an early supporter and never had the impression there would be multiple simultaneous sensors supported. The spec always listed one sensor input port. It does, however, sound like a nice feature for a Twine 2.0!

Grant Hulbert

Thanks, the number of ports didn't register with me, because my computer has only one FireWire port, bit I can connect many FireWire hard drives to it (obviously Twine is not FireWire, but you get the idea). I assumed some sort of bus architecture, or daisy-chaining was going to be standard. It wasn't really made clear that this was one-at-a-time. If it were, I would have ordered just one sensor.

Jim Kirk

Each sensor has a DS2401 IC which provides a unique serial number and single line data bus that allows multiple devices, so I'd think multiple sensors should be possible. SW upgrade maybe?

For hardware, I'd think it should be as simple as a multiple "Y" type adapter thing for TRRS 3.5 mm connectors (like what you can get to connect multiple headphones to an mp3 player).

http://www.maximintegrated.com/datasheet/index.mvp/id/2903

Gerry Mueller

At the moment, since all Twine external sensors are on/off, you can use the break-out board for multiple sensors/switches, as long as they signal on/off. Simply connect them to the break-out board,using a transistor or a relay, in parallel. When one (or more than one) closes, the Twine will "see" this, and take the defined actions. You will not know which sensor triggered, but if you are monitoring "critical" events, you will be warned to check. That's the best that is possible right now.

Gerry Mueller

Further to above, all the switches will have to be the same in the "normal" state, "on" or "off" for this to work. As it appears that external sensors that are "on" consume more power than for "off" it is obvious which the normal state should be.