Differences

This shows you the differences between two versions of the page.

--- info:wallbox_conversion_blog [2015/05/08 07:56] – created 174.97.189.204
+++ info:wallbox_conversion_blog [2015/05/08 08:29] (current) – 174.97.189.204
@@ Line 22: / Line 22: @@
 {{:info:wallbox_if_schematic.png?400|}}\\
+For the uninitiated, an Opto-isolator is an LED and a light activated transistor bundled into a single chip – it’s like a relay. In my case a DIP. The left of the circuit connects to the Wallbox’s 25vAC and Signal terminals; the right connects to the RasPi. I also hooked up 4 LEDs to the Pi to provide some kind of debug output in the event of software errors.
+{{:info:wallbox-pi.jpg?400|}}\\
+===== Decoding Pulses =====
+As I eluded to above, the key combination is electrically pulsed by a rotating arm. Steve had the good fortune of having an oscilloscope to hand; I sadly didn’t. Rather, I started on the code that would decode the pulses and, initially, used it as a timer. It was clear, after filtering jitter, that the pulse train had a clear time gap in it. In Steve’s case, this gap represented a break between the letters and numbers. In my case, it represented the 20s in a base 20 numbering system.
+The pulse train is sequential to represent A1 through to K0. If X represents the number of pulses before the gap and Y represents the number of pulses after the gap, X increments from 1 to 20 whilst Y stays at 1. Y then increments and X resets back to 1. The cycle repeats through to X=20, Y=4 for K0.
+The maths was thus:
+  * Unordered List Item
+  * Decrement both the pre and post gap counts as 0 is represented by 1 pulse
+  * The letter is (2 * post-gap-count) + (1 if pre-gap-count is > 10)
+  * If letter was worked out to be > ‘H’, add 1 as the wallbox doesn’t have an I
+  * The number is the pre-gap-count modulus 10 (i.e. pre-gap-count % 10)
+Handling kernel level interrupts came with some problems of its own. Most notably, having to think sort-of-thread-safe when writing the code. The interrupt can… well… interrupt code processing at any time. If this is part way through a calculation, things get funky. This code is what I came up with. (see phil lavin seeburg.c)\\
+===== Interfacing with Sonos =====
+The Sonos “API” is a UPNP bastardization and is, frankly, horrible. PHP being my strongest language, I thought this the best way to tackle it (hence the C code’s interface with an external programme). I forked a pretty crappy Sonos class on GitHub and set about fixing/improving it. I’ve added multicast Sonos device detection and, most importantly for my requirements, Spotify support. The resulting code is on my GitHub account. Also here’s my usage of the class. https://github.com/phil-lavin/sonos
+==== Track Cards ====
+The Wallbox can handle 100 tracks. I had to get these into a parsable list for the Sonos code but also to print up some cards to go in the Jukebox. The Spotify API is also shocking. The best course of action I found was to use the Spotify play button generator to make an HTML page with the playlist data and then parse it with some throw-away code. Here’s the throw-away code. Don’t judge me…
+Being a budding designer in my spare time, I knocked up some track card templates in Microsoft Paint. These are below:
+{{:info:jukecard-orange.png?300|}}\\
+{{:info:jukecard-green.png?300|}}\\
+I then used some more throw-away code to populate these with the track info. That throw-away code is here. Again, don’t judge!\\
+{{:info:c1.png?300|}}\\
+I then used some more throw-away code to populate these with the track info. That throw-away code is here. Again, don’t judge!
+I may have stumbled across a loophole in the Staples pricing system as they printed these on cards and individually cut them all out for not a lot of money.
+==== The Finished Article ====
+I mounted it on the wall and put the pi, circuitry, transformer, etc. on the other side of the wall to keep things clean. Picture below.
+{{:info:photo1.jpg?450|}}\\