Intro:

I ordered this nifty ‘RFduino’, an arduino-compatible device which was also my first ever kickstarter purchase over a year ago now.
However, when the device arrived, the company behind it seemed exclusively interested in the iPhone handset to the detriment of all other platforms.
Personally, the lock in monopolistic attitude of Apple and its customers really gets my goat, but I digress.

The lack of support and that the device arrived half a year late left me with a sour first taste of Kickstarter.

Since then, I’ve played with the Rfduino using JT’s iGear (no, I don’t know why fell into the Apple pit either) using the only app available to use the sketch it comes with – the internal thermometer

But that’s rather limiting!! I bought this device with plans to build a Wireless ‘Internet of Things’ sensor network for my house.

I have designs on talking to every platform available using protocols such as mqtt, backends like rrdtool and web interfaces for my housemates to see and control the action.

This is something I’ve been dreaming and sketching out  for years, because lets face it, who doesn’t think having the lights turn out when you leave is super cool?

So without further ado, how do we get the RFduino to talk to a linux machine, in my case a Raspberry Pi running Raspbian.

Ingredients:

Hardware:

• RFduino (assumes preloaded Temperature sketch, but this procedure will work if you are running  a sketch sending a Float value)
• USB Bluetooth 4.0 adaptor (RPi compatible devices here, note must be 4.o [or above])
• Linux computer (Raspberry Pi in my case)

You will need

• Internet connection to download tools
• Bluetooth packages installed (bluez-tools)

Howto:

Power on the  RFduino and linux machine. I used two Alkaline AA batteries to power the RFduino although Rechargeables do work.

Install the Bluetooth 4 usb adaptor on the linux machine
Install the necessary bluetooth programs:

sudo apt-get install bluetooth bluez bluez-utils bluez-firmware

(you may need to reboot the machine afterwards, I don’t believe I did)

Bring up the bluetooth interface:

sudo hciconfig hci0 up

Run a Low Energy scan to find the address of your RFduino:

sudo hcitool lescan

Should elicit results similar to this:
EA:BA:20:48:37:80 (unknown)
88:D8:CD:08:12:FA (unknown)
99:D8:CD:10:66:FA (unknown)
DD:AF:13:17:23:80 RFduino

Select and copy the MAC address given for the RFduino on your system.

(I have no idea why you have to scan as root, someone please leave a comment if you do, and if theres a way to run as a normal user…groups?)

Read the temperature attribute from the RFduino using gatttool. Paste your devices MAC address in instead of mine of course.

sudo gatttool –device=DD:AF:13:17:23:80 –interactive
[   ][DD:AF:13:17:23:80][LE]>
[   ][DD:AF:13:17:23:80][LE]> connect
[CON][DD:AF:13:17:23:80]][LE]>char-read-uuid 2221
[CON][DD:AF:13:17:23:80][LE]>
handle: 0x000e value: 00 00 a8 41 00 00 00 00 00 00 00 00
[CON][DD:AF:13:17:23:80][LE]>disconnect
[   ][DD:AF:13:17:23:80][LE]>quit

Now from that exchange with the RFduino, we have gained a long hexadecimal string.
From a post on the RFduino forum, I learned that the value we want is always after the ’00 00′ string (in bold above).
This is the temperature read from the RFduino’s internal sensor * 8.
So we need to convert this to Decimal and divide by eight to retrieve the temperature value in celsius (American readers, why aren’t you on SI units yet? :P).

Convert the hex value to decimal temperature

decimal=$((0xa8))
decimal=$(($decimal/8))
echo $decimal
21

The above method returns an integer value. This is because Bash has limitations working with numbers that are not whole (decimals).
Workarounds use the command bc to interpret string inputs as decimal numbers. I think there is a method to define variable types in bash, but I didn’t get very far with this.

My attitude is that once you start hitting the limitations of a shell scripting language, it’s time to migrate to a proper programming/interpreted language (at least python).
Spending hours and using multitudes of additional programs make it work is often pointless.

Just think, if you had to run the script on a embedded system without most of those commands, wouldn’t it just be better to do it in C++?

Next time:

Now that I’ve successfully read the values being sent by the RFDuino I need to figure out how to automate the process – in non-interactive mode.

These commands do the same thing but respond differently

sudo gatttool -b [MAC] –char-read  –handle=0x000e
Characteristic value/descriptor: 00 00 a8 41 00 00 00 00 00 00 00 00

sudo gatttool -b [MAC] –char-read –uuid=2221
handle: 0x000e   value: 00 00 a8 41 00 00 00 00 00 00 00 00

Simple bash script to read temperature in celsius (accuracy is lost here as the decimal is converted to an integer)

#!/bin/bash
stringZ=$(gatttool -b [MAC] –char-read  –handle=0x000e)
stringZ=${stringZ:39:2}
hex=$((0x$stringZ))
decimal=$(($hex/8))
echo $decimal
exit

don’t forget:
chmod +x [whatever you called the script]

and run it as root:
sudo [whatever you called the script]

Afterword:

I won’t pretend to understand the naming conventions of Bluetooth 4.0/LE.
I don’t! I spent a whole day looking into it and could not find a single source that easily explained the structure, naming, and profiles. If someone has seen something good, please post in the comments!

It’s frustratingly close, like I can see there is a neat logic to it, but I just don’t care to spend any more time trying to figure it out, when all I want to do is use it. This does make it slightly more hacky and less neat and quick of course, but that’s life!

Sources:

gattool commands to read the sensor:
http://lilyhack.wordpress.com/2014/02/03/ble-read-write-arduino-raspberry-pi/

howto convert hex to decimal on the command line:
http://linuxcommando.blogspot.co.uk/2008/04/quick-hex-decimal-conversion-using-cli.html

howto do calculations on the command line:
http://www.tldp.org/LDP/abs/html/arithexp.html

Hacked up way of using gatttool non-interactively, using ncurses and a python script:
http://thomasolson.com/PROJECTS/BLE/RFduino/LINUX/

Bash string manipulation:

Bash String Manipulation Examples – Length, Substring, Find and Replace

Others:

http://joost.damad.be/2013/08/experiments-with-bluetooth-low-energy.html

So I just noticed that our beep music post has become popular enough to have been reddited, and used as a source in a video!

So thanks for that guys and girls of the interwebs! I almost feel appreciated!

In recognition, I thought I’d list our referrers, and possibly some beep music. Maybe we can become a repository for this kind of stuff.

#0 So you have a shiny new Raspberry Pi, and you want to make some noise?

You can in fact make beep music on the raspberry Pi!
All you need is a Piezo thingy (transducer or beeper or whatever it’s called)
(Available from Maplin in the UK: 3v ceramic Piezo transducer only £1.29 as of 2/2/14!!)

Thanks to Kronalias (is that a linux reference there? `alias kron=’crontab’`)?

#1 Here’s a video from smeezekitty on youtube:

From the comments: running beep music on a 486!

Reminds me of this old beastie of JT’s:

Still working in 2014! I am in fact a IBM Thinkpad 380z with a PII processor, 64mb of ram, and most inexplicably a 40GB hard drive. I also have a very loud beeper which will hurt your ear if you are next to me when it goes off. Lucky i have a volume knob.

I will definetely try all the beep codes that have been submitted in the comments so far on this awesome machine, and I promise to make a video of it if I get three more beep-songs to add to our beep music tracks. (I might even make an Album…on tape cassette [if i can find one haha], or maybe just put it onto a floppy disk if and mail it to you guys [if i can find one that works ROTFL])

#2 The redditors of the web have heard of us!

It must be true if there’s a screencap of it!

#3 We were linked to on Stackoverflow

I can’t be figged to give you that link or clip an image, so here’s a link to another source posted.

Ubuntuforums: What is your favourite ‘beep’ song?

I couldn’t find Chop Suey in beep music, but with the work done in #3, it shouldn’t be too hard to translate!

Next time I’ll have to compose something entirely new!!

This is part three of my autobiography so far. Part one is here. Two is here.

So, just before I went to secondary school (age 12+) for the first time, we went to a covie camp. This was important for one main reason. During one of the sermons, we were shown a film, and whilst watching, I had an moment of absolute clarity, and total conviction. Christianity is true, there is a God, and he does love me. You know, typing that will never not be strange.

I broke down crying. I remember that moment as if it were an hour ago. I became a Christian. So, in a weird sort of way, my parent’s divorce kinda led me to converting to Christianity.

About year two or three of secondary school, I started going to visit the school counsellor. I remember nothing of those visits, only that they were helpful. During that time, I shunned friends, and mainly stayed in the school libary during my free time, or read books. I used books as an escape, leaving this world for different ones, preferring anything strange or different. I stripped through crime, fantasy and science fiction books rapidly. I also volunteered to help in the school library, putting books away, keeping it tidy and neat.

At some point, the school counsellor left, and a new one arrived. I didn’t gel with the new counsellor at all, and so didn’t go back. That would be my last counselling session for quite some time. Time passed.

At some point during this time, I felt snubbed by the librarian, a silly thing, I felt I’d been passed over for some additional responsibility. Additionally, I had a very brief ‘girlfriend’ and a relationship that I wouldn’t really engage at all with. That also led to an embarassing suituation a little while later, which I won’t repeat, which helped solidify my intent to remain a bachelor for some time, and would be the only time I briefly had a girlfriend, or any sort of significant other, to date.

Watching the solar eclipse at a covie camp

I switched from volunteering at the school libary, to helping out in the school IT suite, spending any spare time playing with the computers. I was the source of at least two spates of communication tools getting around the IT department’s lockouts to prevent them, since I just continually played with the sandbox I was given. For those geeks, at this point we were running windows XP. I however didn’t keep my mouth shut about the ways to talk to other pcs, and they spread like wildfire around the school, till they were locked down.

That was the first point I really got interested in computers.

During all this time, we had an… interesting contact schedule. Dad got us 2 and a half weekends out of every 4, and a weekday evening. We were with mum the rest of the time. Dad was at this point working for Kleeneze, delivering catelogs and taking orders. Since mum and dad didn’t really get on, or talk that much at all, we had basically different responsibilities and rules at each place. To an extent, we just got used to it. Mum and dad took turns to have us christmas, with the other parent having us over new year.

New year 2000, the milienium, I was at a relatively boring party at my church. I never did really get the whole new year thing, and to this day I still don’t.

Eventually, I did A-levels. I am the proud bearer of 2 A levels in vocational Information Comunication Technology, or in other words, how to use Microsoft Word. I only got a C in that, mainly because I was bored out of my mind, and the spec was just a bit mad. We did get taught some useful snippets though, I learnt basic binary and database normalisation. That was also the first time I created a website.

Next up, my first job.. To Be Continued…