Yet Another Fine Thing: TI SensorTag CC2650

Yet Another Fine Thing: TI SensorTag CC2650

[1]Christoph and I exchange gadgets occasionally, and he sent me a
[2]SensorTag, which is a [3]small little red thing with contains a
bunch of sensors on it: a temperature sensor, a 9-axis motion sensor,
a humidity sensor, an altimeter and pressure sensor, and an ambient
light sensor. In addition to two buttons, the [4]SensorTag also has a
reed switch on it which I can activate with a magnet, and it has a
buzzer (which I thought didn't work until I held the device to my
ear). Apparently it also has a serial flash on it for storage and OTA
upgrades, and a battery. The [5]teardown suggests it also has a
microphone. The package is enclosed in red rubber which feels nice,
and which can easily be removed to disclose a small, rectangular,
plastic case with a transparent lid.

SensorTag

I spent an hour looking for information on the [6]SensorTag, reading
some articles about it, and generally attempting to get a feel for
what it's supposed to do, but I'm having trouble finding real
use-cases for it. As a consumer for this "Thing" there is too much I
don't understand on the Texas Instruments [7]SensorTag page. For
example:
* The SimpleLink(TM) SensorTag allows quick and easy prototyping of
IoT devices. How? What does this mean?
* IoT made easy, with a secure connection to the cloud. Maybe, but
you need an app on a smart phone for that.
* The SensorTag comes in two variants. One of them is "coming soon"
* Low-power or battery-less operation. Which shall it be?
* Remove the barriers between software and hardware. How's that? I
need the hardware (SensorTag) and the software (an app).
* With the SensorTag app, you can build your own iOS app in minutes.
It allows quick and easy prototyping of simple sensor applications..
There is absolutely no indication whatsoever that the iOS app "lets me
build my own iOS app in munutes" or that it lets me do "easy
prototyping of simple sensor applications". Maybe what they mean is
server-side, but that's certainly not what the [8]blurb says. Or do
they mean a bit of drag and drop [9]as shown in this video?

The getting started tab of the [10]SensorTag page says I should
download the app, remove the battery tab (so it does have a battery,
eh?), and I can then "explore" my SensorTag. Yes, that works, as the
following screenshot depicts, after I figure out that I have to poke
one of the rubber buttons on the tag to allow it to be discovered.

iOS app

I then find out by experimentation that I have to switch on the
sourcing switch at the top of the app; this enables the app to push
data to "the cloud", and I can click on a link which takes me there:

The Web page updates the device data instantly. I forget where
exactly, but I stumbled over the fact that the sensors' data is also
published to an IBM MQTT broker which I can subscribe to with any MQTT
client, replacing the xxx in the subscription topic by the device ID
which is displayed on the above IBM Internet of Things Foundation
page. The MQTT topics are documented [11]here.
mosquitto_sub -h quickstart.messaging.internetofthings.ibmcloud.com \
-v -i a:quickstart:jp01 -t 'iot-2/type/+/id/xxxxxxxxxxxx/evt/+/fmt/
+'
iot-2/type/"multitool-app"/id/6e97b598fe86/evt/status/fmt/json {
"d":{
"key1":"0",
"key2":"0",
"AmbTemp":"21.65625",
"IRTemp":"17.625",
"humidity":"48.92485",
"baroPres":"999.24",
"baroHeight":"-0.08738943",
"accX":"0.004211426",
"accY":"0.00402832",
"accZ":"-0.2452393",
"gyroX":"-1.237335",
"gyroY":"1.867676",
"gyroZ":"-0.6459045",
"magX":"-1.798828",
"magY":"66.55664",
"magZ":"-10.04346",
"optical":"151.56"
}
}

I did not format this payload; the formatted JSON string you see is
what was transmitted, and it makes me shudder slightly because it
makes scripting difficult. The monitoring topic doesn't do that, but I
do wonder who thought up the double quotes within the topic name:
iot-2/type/"multitool-app"/id/6e97b598fe86/mon { "Action": "Connect",
"Time": "2015-11-24T07:16:46.294Z", "ClientAddr": "192.168.212.64", "C
lientID": "d:quickstart:\"multitool-app\":xxxxxxxxxxxx", "Port": 1883,
"SecureConnection": false, "Protocol": "mqtt-tcp", "ConnectTime": "20
15-11-24T07:16:46.293Z" }

Christoph wrote a nice little program which subscribes to that data
stream and prints this out:
$ DEVICE=xxxxxxxxxxxx ./ti_from_ibm.py
magZ magY gyroY IRTemp baroPres baroHeigh magX
accY accX accZ gyroZ gyroX humidity AmbTemp
optical
18.43799 96.83691 0.1634216 20.5 1012.35 -0.603385 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.73907 24.5625
0.48
18.43799 96.83691 0.1634216 20.375 1012.31 -0.258004 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.73907 24.5625
0.48
18.43799 96.83691 0.1634216 20.40625 1012.28 -0 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.73907 24.5625
0.48
18.43799 96.83691 0.1634216 20.34375 1012.31 -0.258004 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.73907 24.5625
0.4
18.43799 96.83691 0.1634216 20.40625 1012.31 -0.258004 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.73907 24.5625
0.48
18.43799 96.83691 0.1634216 20.46875 1012.26 0.1727007 56.06348
0.0057983 0.0003662 -0.244995 0.1089478 -0.910491 53.617 24.5625
0.48
19.3374 95.9375 0.2957153 20.59375 1012.27 0.0863499 55.16406
0.0075683 -0.001159 -0.244689 0.0077819 -0.8638 53.617 24.5625
0.48

The program itself is quite simple:
#!/usr/bin/env python
import paho.mqtt.client as paho
import json
from os import getenv

device = getenv('DEVICE')

def on_connect(mosq, userdata, rc):
mqttc.subscribe('iot-2/type/+/id/%s/evt/+/fmt/+' % device, 0)
print "%9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s
%9.9s %9.9s %9.9s %9.9s %9.9s" % ( "magZ", "magY", "gyroY", "IRTemp",
"baroPres", "baroHeight", "magX", "accY", "accX", "accZ", "gyroZ", "g
yroX", "humidity", "AmbTemp", "optical")

def on_message(mosq, userdata, msg):
data = json.loads(str(msg.payload))
d = data["d"]
print "%9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s %9.9s
%9.9s %9.9s %9.9s %9.9s %9.9s" % ( d["magZ"], d["magY"], d["gyroY"],
d["IRTemp"], d["baroPres"], d["baroHeight"], d["magX"], d["accY"], d["
accX"], d["accZ"], d["gyroZ"], d["gyroX"], d["humidity"], d["AmbTemp"]
, d["optical"])

mqttc = paho.Client(client_id="a:quickstart:%s" % device, clean_sessio
n=True, userdata=None, protocol=3)
mqttc.on_connect = on_connect
mqttc.on_message = on_message

mqttc.connect("quickstart.messaging.internetofthings.ibmcloud.com", 18
83, 60)
mqttc.loop_forever()

The documentation of this device is spread all over the place and the
fact that there have been two versions of it doesn't help at all. Some
documentation is an a TI Wiki. The [12]CC2650 SensorTag User's Guide
for example, warns about a pre-production FW image, but the app
through which upgrades are apparently possible doesn't show newer
firmware versions being available.

Another link from the [13]SensorTag page takes me [14]here where I see
`mqtt' [15]linked to. There I see I need a "free Temboo account", and
I have to "register with Twilio" where I get a phone number, and then
I require a "Pagerduty account" and an API key, and, then I need a
"Zendesk account", ... I very quickly closed that Web browser tab and
shuddered. Gals & boys, if that's what we need for the "Internet of
Things", we're going to have 50 billion squared problems by the year
2020!

There's also a [16]quick guide to making a mobile app for the
SensorTag which I haven't tried, because I don't see the point in
creating a mobile app which displays the sensor data if I have to run
the TI SensorTag app anyway.

Be that as it may I went in search of how to talk to the device
directly, or rather, how to have the device talk to me, and [17]found
this.

After inserting a [18]BLE-capable Bluetooth dongle into a laptop, I
could actually scan for LE devices, and I learned that there may be
one connection to a BLE device only, so I close the SensorTag app
before attempting the scan:
$ hcitool -i hci1 lescan
LE Scan ...
B0:B4:48:BD:B8:05 CC2650 SensorTag

and the rest was easy in as much as a chap called Ian Harvey has
[19]done the hard work.
jpmens/cc2650/b0b448bdb805 {"lux": 0.24, "ambient_temp": 25.14, "humid
ity": 48.42047119140625, "target_temp": 21.03125, "tst": 1448289252, "
millibars": 1002.97}
jpmens/cc2650/b0b448bdb805/lux 0.24
jpmens/cc2650/b0b448bdb805/ambient_temp 25.14
jpmens/cc2650/b0b448bdb805/humidity 48.4204711914
jpmens/cc2650/b0b448bdb805/target_temp 21.03125
jpmens/cc2650/b0b448bdb805/tst 1448289252
jpmens/cc2650/b0b448bdb805/millibars 1002.97

Minutes later, I had the device reporting via MQTT [20]using this code
and this doesn't require a cloud service - I'd point this at my own
MQTT broker of course.

After playing with this for a bit I realized that the Python
implementation doesn't appear to cater for all the [21]SensorTag's
capabilities (i.e. sensors). I then found [22]node-sensortag which
does, and cobbled up [23]something which publishes an MQTT payload
whenever one of the sensors on the tag notifies NodeJS. This module
also supports the buttons and the reed switch, and it auto-discovers
the [24]SensorTag proper, so I don't have to configure it with the
device identifier. The result, using [25]Freeboard with the MQTT
plugin gave me this:

Freeboard

As a [26]BLE device, the SensorTag literally "goes away" when it's too
distant from whatever is receiving the data, be it the iOS app or the
BT dongle in my laptop. I assume that the makers wanted the
[27]SensorTag to be carried in one pocket, with the cloud-connected
smart phone in another. I just don't know. The [28]SensorTag
specifications state that it can be toggled between Bluetooth Smart,
6LoWPAN and ZigBee and, as mentioned above, there is to be a WiFi
version some time.

The [29]SensorTag is small enough to be placed almost anywhere, and as
it doesn't need wiring, it would be nicely suited as an ambient light
sensor to control, say, [30]openHAB: an appropriate [31]BLE dongle on
an openHAB box in Bluetooth reach, and Bob's your uncle. (BTW, the
ambient light sensor is appears to be very good.) Christoph also
suggests using it to determine whether your spouse drives more
aggressively than you do, by monitoring the accelerometer. ;-)

If and when the WiFi version comes, and if it's comparable in price to
the BlueTooth version (USD 29.00), I could imagine getting two or
three to use as temperature and luminescence sensors in the house.

References

1. https://ckrey.de/
2. http://ti.com/sensortag
3. http://www.ti.com/ww/en/wireless_connectivity/sensortag2015/tearDown.html
4. http://ti.com/sensortag
5. http://www.ti.com/ww/en/wireless_connectivity/sensortag2015/tearDown.html
6. http://ti.com/sensortag
7. http://ti.com/sensortag
8. http://www.ti.com/ww/en/wireless_connectivity/sensortag2015/appsAndPartners.html#main
9. https://www.youtube.com/watch?v=UhMKG761l78
10. http://ti.com/sensortag
11. https://docs.internetofthings.ibmcloud.com/messaging/applications.html#/
12. http://processors.wiki.ti.com/index.php/CC2650_SensorTag_User's_Guide
13. http://ti.com/sensortag
14. https://www.temboo.com/hardware/ti
15. https://www.temboo.com/hardware/m2m-mqtt
16. http://evothings.com/quick-guide-to-making-a-mobile-app-for-the-ti-sensortag-using-javascript/
17. https://smidgeonpigeon.wordpress.com/2015/07/21/raspberry-pi-2-ble-ti-sensor-tag/
18. https://en.wikipedia.org/wiki/Bluetooth_low_energy
19. https://github.com/IanHarvey/bluepy
20. https://gist.github.com/jpmens/4bbe165b19a2b0d457c6
21. http://ti.com/sensortag
22. https://github.com/sandeepmistry/node-sensortag
23. https://gist.github.com/jpmens/af90e8f87254226d0dd5
24. http://ti.com/sensortag
25. https://jpmens.net/2014/11/12/freeboard-a-versatile-dashboard/
26. https://en.wikipedia.org/wiki/Bluetooth_low_energy
27. http://ti.com/sensortag
28. http://ti.com/sensortag
29. http://ti.com/sensortag
30. https://jpmens.net/2014/01/14/a-story-of-home-automation/
31. https://en.wikipedia.org/wiki/Bluetooth_low_energy