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Enchanted Objects

19 Posts authored by: crjeder
crjeder

Finalisation

Posted by crjeder Jun 24, 2015
Time is up! And I am not done yet. So I have to pack my stuff and present what I have achieved in the past 16 weeks.   Smart Key Hooks  What are smart key hooks? Or what are key hooks anyway? Basically they are a place to hang your keys like this: But for me it is a little more. By looking at it I know who's at home and who not and it is used to exchange important messages between family members: (The mess is just utensils you want to reach from the doorstep.) As is it works perfe ...
Linux support for 10-bit Slave Addressing The I2C protocol knows about two kinds of device addresses: normal 7 bit addresses, and an extended set of 10 bit addresses. The sets of addresses do not intersect: the 7 bit address 0x10 is not the same as the 10 bitaddress 0x10 (though a single device could respond to both of them). I2C messages to and from 10-bit address devices have a different format.See the I2C specification for the details. The current 10 bit address support is minimal. It should ...
crjeder

Thoughts on Privacy

Posted by crjeder Jun 12, 2015
An interesting research paper about security vs. privacy. It is about securing the home through "smart" internet connected locks and how it could allow parents to spy on their teenage kids. When the kids circumvent the system in order to regain privacy security is even lower than with a "old-school" solution. It is relevant to this project because very similar audit logs are produced by the smart key hooks. The information smart key hooks collect is "text-only" which is better accepted by the s ...
crjeder

More Datasheet Studying

Posted by crjeder Jun 11, 2015
Some of you might have recognized that I omitted one significant detail in the C code in my last post "Use WS2812B on the SAMA5D4 Xplained": How is the correct PWM clock frequency of 2.4 MHz configured?   Clocks, Clocks and more Clocks The peripherals of the SAMA5D44 (no, this is not a typo, that's the name of the SOC on the SAMA5D4 Xplainded board) all receive their own clock signal. Relevant for PWM is the peripheral clock as shown in the diagram from the datasheet (page 1448): Most c ...
More Details on the WS2812B  The mysterious signal from my previous post was for a WS2812B LED. It was shown in Fairy Dust has arrived!. It is a RGB LED with integrated controller. The LEDs can be easily chained together:   If you are really crazy you can build something like this with those:   With an estimated power draw of 3 KW and 10.000 WS2812 LEDs this is really insane.   But back to the lab: Besides of the power supply the LEDs use only a single pin for data ...
Let us assume that I want to create a signal like this:   Where:   Signal Name Duration in μs ± 150 ns T0H 0.4 T1H 0.8 T0L 0.85 T1L 0.45 Treset > 50   The usual way to generate arbitrary signals is called "Bit banging". It requires software to set the output in the "HIGH" and "LOW" state in the exact timing given by the protocol. The timing requirements for this signal look pretty strict that I do not believe that this would be possible or at least not ve ...
crjeder

Planing the Final Spurt

Posted by crjeder May 27, 2015
Inspired by jancumps post 1958 Turntable from the Black Forest - 21: Right-Sizing my Plans I decided to plan the last 5 weeks of the challenge and look back on what I've achieved.   Looking Back  The features I've promised are: No user interaction necessary besides hanging the keys Make key status available on-line RGB-LEDs to display status of the absent persons RESTful / IFTTT  / Tasker (android) interface Additional, optional features I have proposed: Record speech mess ...
crjeder

Next Road Block

Posted by crjeder May 13, 2015
I've identified an other road block: The RGB LED Lighting Shield uses 10-bit I2C addresses! I found a good explanation here. Should not be a big problem but standard tools as i2cdetect only work with 7-bit addresses. Let's how it works. ...
I am one of those who took the challenge to use the SAMA5D4 from the kit. My take on it is to boot using nfs mounted root file system. This would have the advantage that I would have as much space in the root file system as I need and that I could easily do changes to the rootfs without flashing the board again and again. This should dramatically speed up the development process. Obtaining the rootfs Image  I'd like to use one of the large standard distributions so I look for a debian port ...
Today I've soldered the first prototype of the key fob: Please forgive the very raw prototype. As 1-wire device I've used the DS2401 which provides the ID only (as opposed to my earlier test where I used an EEPROM), because it is the cheapest 1-wire device I could find. Unfortunately I was not able to get them in the SOT-223-3 package which is the smallest package I might be able to solder. Instead I went for the TO-92-3 package which is through hole and easy to solder. On the upper side of ...
Requirement  Before integrating LEDs I have to revise the communication protocol since the necessary information was not present before. Furthermore some properties are missing. The protocol should be: Future proof Secure Safe against transmission errors / modified communication Following information was not present in the previous protocol: Key status changes LED status LED status will be changeable by the client.   Message Protocol  This is the specification of the vers ...
I recognized that I tend to post only positive results but at the same time I learn a lot from the mistakes of others I decided to devote this blog to my time wasting effort of interfacing 1-Wire components from node.js. Several evenings I read blog post, documentation and code just to find out what I am doing wrong - with no result. It still did not work. Owfs was not able to detect the devices nor could the linux kernel show me the information in the /sys/bus/w1/ directory. I was a bit frustra ...
crjeder

Smart Key Hooks Client

Posted by crjeder Apr 20, 2015
I started my "career" in electronics not long ago when the first Raspberry PI became available. But looking on the specs I decided that the BeagleBone Black suits my needs better and bought one. What I liked most about it after playing with it for a while was the c9 IDE and node.js. Therefore I decided to do the programming for this challenge in node.js, too. The Cloud As the cloud service I have chosen Pushbullet because it has: an easy, restfull API clients for all OSes integration in ...
crjeder

Identifying Keys

Posted by crjeder Apr 7, 2015
Crucial to my design is the ability to detect and identify keys. The potential solutions are divided into following categories: wireless, wired and explicit. The later means the user explicitly states „this is key #11“ through some interface. This is the least desired one and will be the fall-back if everything else fails. Therefore let's concentrate on the other two. Wireless Because of the popularity of RFID tags wireless identification was the technology I thought about first w ...
crjeder

Happy Easter!

Posted by crjeder Apr 5, 2015
I wish everybody a Happy Easter. Thanks Element14 for this cool competition and to all patient readers and to the helpfully and skilled participants. Unfortunately there was not much progress on the competition from my side. But as an status update: I am looking for a solution to identify keys. Here a sneak preview: And to distract you from the challenge: Go outside it's spring! (ok, northern hemisphere only ;-) ...