This post shows how I set up a Live Web Dashboard from a Raspberry Pi as seen in the video above. In case you haven't worked it out, what's going on here is the Raspberry Pi is using 3G to send GPS and accelerometer data up to ControlMyPi. Users can then log in to ControlMyPi and watch the Live data displayed on the dashboard. In this case I'm using Google StreetView and Maps to show the current position and heading. Gauges are used to show speed and X,Y and Z accelerations.
(Special thanks to Rasathus for making this video for me!)
The diagram below shows the data flow:
There are quite a few guides out there for setting up 3G dongles on Raspberry Pis. Some use what now seems to be an unsupported script called sakis3g - I tried this first but was uneasy about using something that the author appears to have taken down. In fact all I had to do was install usb-modeswitch and wvdial. usb-modeswitch automatically detects your dongle and switches it into TTY mode. Simply use apt-get to install it.
wvdial is used to make the PPP connection. After using apt-get again to install it I followed the instructions on Linux Forums to get my connection up and running.
Start-up sequence: There's probably a better Linuxy way of doing this (maybe someone can comment to let me know) but I needed to be in control of the order that things started up to help with TTY discovery and smooth networking. I'm using a TextStar serial LCD through a USB to serial converter and my code expects to find it on /dev/ttyUSB0 so I really don't want the 3G dongle to appear on USB0. Also, I found that if my code starts trying to use the network before the PPP link is up it doesn't work and you have to stop and start the program. This is no good if you're out on your bicycle somewhere. So I wrote a small boot up script which is run from /etc/rc.local it guides the user through this sequence:
- Remove 3G dongle and power up Raspberry Pi
- Raspberry Pi boots up and runs rc.local
- LCD shows "Insert dongle and press 'A'"
- User plugs in dongle and waits for Blue LED before pressing the 'A' button on the TextStar
- LCD shows "Starting 3G please wait"
- wvdial is started
- Few seconds delay to wait for the network to come good
- Start up Bicycle Telemetry app
I'm using the Adafruit Ultimate GPS Breakout - 66 channel w/10 Hz updates - Version 3. I chose this one because having a 10Hz update fitted well with the code design. As you'll see when I publish the code, the main loop is timed off the updates from the GPS. Although I'm not updating the Web Dashboard as quickly as this I am logging this information to file 10 times a second.
The breakout board is simply connected up to the TTL serial pins on the Raspberry Pi and then it appears on /dev/ttyAMA0. When I wrote the code I didn't realise that gpsd existed so I have some code which decodes the serial stream directly, it's pretty simple though. Also I can't see how you can send the settings commands through to the GPS module from gpsd - I'm sending commands to switch the baud rate to 38400 and put it in 10Hz update mode (see PMTK_SET_NMEA_UPDATERATE in this pdf). Without these settings it defaults to 9600 baud and 1Hz updates.
3 Axis Accelerometer
Another Adafruit board is used here - the ADXL335 this senses up to 3g in X,Y and Z directions. I've then used an MCP3008 to convert the analog voltage outputs to 3 digital readings available over SPI. This uses the same technique (and code) from my article: Raspberry Pi hardware SPI analog inputs using the MCP3008.
I have created the cloud app ControlMyPi to make projects like this not only possible, but easy. A client library is used on the Raspberry Pi and all communication between it and ControlMyPi are over XMPP (also known as Jabber) protocol. This is the instant messaging protocol used by Google Talk as well. By using XMPP you're not hampered by firewalls and such but you do have near real-time messaging.
ControlMyPi also makes it simple to serve your live data to multiple web clients using "push". Updates from your Pi are routed through ControlMyPi and "pushed" to the web browser of anyone viewing the dashboard without refreshing pages.
More information about ControlMyPi is in my previous article: Control My Pi - Easy web remote control for your Raspberry Pi projects. Just as a teaser for the next post here is the panel definition code for the Bicycle Dashboard:
[ [ ['S','locked',''] ], [ ['O'] ], [ ['P','streetview',''],['P','map',''] ], [ ['C'] ], [ ['O'] ], [ ['L','Speed'],['G','speed','mph',0,0,50], ['L','Height'],['S','height',''] ], [ ['C'] ], [ ['L','Accelerations'] ], [ ['G','accx','X',0,-3,3], ['G','accy','Y',0,-3,3], ['G','accz','Z',1,-3,3] ], [ ['L','Trace file'],['B','start_button','Start'],['B','stop_button','Stop'],['S','recording_state','-'] ] ]
Here I'm using Picture widgets (P) for 'streetview' and 'map'. ControlMyPi allows you to push an update to an image by sending a url from your script, so the Google Maps Image APIs work very well. I'll show exactly how this is done in code in the next post.
Since I can't be riding around 24x7 I have set up a script which plays back recorded data from a few journeys. This script is running on a Raspberry Pi and sending out the data to ControlMyPi at the correct speed so it's a pretty good simulation. I've set it up as a public panel so you can access it from the front page - or this link: Replay of bicycle telemetry.
The next post will guide you through the code for all of this, coming soon...