This document summarizes a presentation given by Reid Carlberg of Salesforce on building a DIY wireless sensor network. The presentation covered using Arduino, XBee, and Raspberry Pi devices connected over a wireless network to send and receive sensor data via REST APIs and a streaming API. It included details on components, wiring, communication protocols, and lessons learned from prototyping the system.
1. DIY Wireless Sensor Networks
18 Nov 2013, 9:00am, Dreamforce
Reid Carlberg, Salesforce.com, Director - Evangelism
@ReidCarlberg(Link)
Update: 30 Jan 2014 (a)
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3. We’re Building a Wireless Sensor Network
REST API
XBee
Streaming API
Node JS
http://github.com/ReidCarlberg/DF13_WirelessSensorNetwork
4. Hands on making is the best way to learn
connected device app development.
5. Arduino – Open Source Prototyping Board.
ATmega328 Controller
32k of RAM
Easy to program (~C++)
No SSL.
Arduino Classes here Tues & Thurs
9. Bill Of Materials
Arduino Experimenter’s Kit: $85
Arduino XBee Shield: $25
XBee Pro Series 1 (2): $76
Raspberry Pi Starter Pack: $105
Xbee Adapter Kit: $10
Salesforce Developer Edition: FREE
9V Battery: $2
Total: $303
10. Breadboards
+/- conduct up and down.
#’s conduct side to side
A,b,c,d,e, etc don’t matter
Voltage goes to + (red)
Ground goes to – (blue)
Put component leads in different #
rows – up and down, not side to side
11. Wires
Red or Orange – Positive
Black or Green – Negative
Otherwise doesn’t matter
12. Polarity Sometimes Matters
Positive is voltage in.
Negative is voltage out.
Matters on: LED, TMP36
Doesn’t matter on: RESISTORS,
PIEZO
On an LED, the long lead
is POSITIVE.
17. Add Components to Breadboard
LED: Positive lead up
Positive Leads
TMP36: Flat side, right.
Put things in the F column
toward the center.
+
+
+
18. Add Components to Breadboard (optional view)
“Fritzing” Style illustration
Note the vertical bars on
right – polarity reversed!
Careful:
RED & BLUE
REVERSED
19. Add Resistors to Negative LED leads
Resistors connect
negative LED leads with
GROUND.
Remember Fritzing may
not match your board!
23. Connect TMP36 – PLEASE DOUBLE CHECK
Middle to A0
Top to - / Blue (Ground)
Bottom to + / Red
Polarity Matters here –
reversed wiring will result in a
VERY HOT TMP36.
24. Plug In The Battery!
Purple & Green Light = initializing.
Purple (flashing) = Xbee activity
Green = ready
Red = alarm
Disco Lights = DISCO
If you smell something burning your
TMP36 is wired wrong. Disconnect your
battery, wait for it to cool & try again.
25. Raspberry Pi in action
Connected to the network.
GPIO cable to breadboard
XBee to TTYAMA0
27. Communication Protocol
To Arduino
To Raspberry Pi
^Address:Messagen
REST format (single line)
Address = 2 char
{
Message = 5 char
“addr”:”A1”,
Specific Unit Ex: ^A1:ALARMn
“msg”:”hello”,
All Units Ex: ^00:DISCOn
“detail”:”tmp36,alarm,disco”
}
29. Lessons Learned
Prototype, not production.
Test with a meaningful # of devices.
Easy to set up race conditions.
Arduino is limited.
Simple communication protocols are better.
