Category: embedded

Not much to say here. I’ve been using the garage door opener for many months and it just works and is very stable.

dwm@pi1:/home/dwm% uptime
 3:33AM  up 123 days,  4:25, 1 users, load averages: 0.40, 0.15, 0.10

dwm@pi1:/home/dwm% psg mcpigdod
USER  PID  %CPU %MEM   VSZ   RSS TT  STAT STARTED        TIME COMMAND
dwm   930   0.0  1.2 46452 11372  0- S    22Aug16  1748:10.15 mcpigdod

On Wednesday night I stuffed the enclosure with the Raspberry Pi, buttons, indicators and POE splitter after making all of the internal connections. I assembled the second Neutrik dataCON on the second rotary encoder. I temporarily taped my enclosure to the garage wall for testing, and connected the rotary encoders, door activation wires and the POE connection. I also attached the second magnetic door switch to the wall above the south door, and attached the magnet to the top of the door. I then did some basic testing. Both doors work correctly via the web app from my iPhone, and the rotary encoder connections work correctly.

On Thursday night I extended the wiring for the magnetic door switches (soldered joints and heat shrink), then sleeved the extensions with gray braided sleeve. Since I’m still waiting for a Neutrik jack for these, I’m temporarily using a dual row barrier strip to connect them to my PCB inside my enclosure.

I received my HAT PCBs that I designed for the garage door opener. I populated one of them and tested all of the outputs as well as the door closed switch inputs. Everything works. Yay! I will continue assembly tomorrow, and possibly test it wired into the garage doors.

Today I connected the wiring for door activation from the garage door openers to the new screw terminal keystone jacks in the new wall plate in the garage. I also connected the cat5e to the yellow keystone jack. I then installed the new wall plate (stainless steel) into the new wall box. It looks clean and tidy, and I tested the door activation wiring.

I fabricated the remaining part of the rotary encoder mounts from electrial grade fiberglass angle. Both of the rotary encoders are now mounted.

I terminated the POE connection in my Leviton structured media enclosure in the basement. The jack is a yellow Leviton QuickPort, to identify it as needing POE. I used my Rhino labeler to put a heat shrink label on the cat5e cable before I punched it down on the jack. The jack is in a new Leviton 12-port jack panel that I bought to keep my POE jacks separate from non-POE jacks.

I installed the new POE switch in my rack in the basement. I then assembled a short cat5e patch cable and connected the POE switch to my main switch. I then connected one of the POE ports of the new switch to the new jack that leads to the wall plate in the garage. I connected my Raspberry Pi in the garage with a POE splitter. It works fine.

I drilled two more holes in the enclosure for the Raspberry Pi, and installed cable glands. One is for the wires to activate the garage doors, the other is for the cat5e cable. I haven’t decided how I’m going to connect the door switches yet. I’m leaning toward using a single Neutrik speakON 4-pole connector.

Tonight I finished running cat5e from the new wall plate box in the garage to the basement. This was a difficult, sweaty job climbing around on trusses in the attic with fish tape (it was over 95F during the day today). But it’s done. I will terminate the ends with new jacks tomorrow.

Over this week I did some work on the enclosure for the Raspberry Pi, my HAT, buttons, indicators, POE splitter and jacks. I installed two Neutrik etherCON jacks in the enclosure for the rotary encoders, since those are on the top of the enclosure and I want to keep dust out of the connection. Fortunately the rotary encoder wires are correctly sized to use with a crimped RJ45. The door activation buttons and door status indicator LEDs are installed in the front cover. Everything appears to fit, though I will not receive my custom PCBs until Monday and hence can’t assemble the whole thing until next week.

I am also waiting on some cable glands, keystone inserts for the door activation wiring and the rotary encoder mounting piece I designed (which I ordered from Front Panel Express).

I ordered brackets of my design from Front Panel Express to mount the rotary encoders.

I ordered Lovejoy couplings and fasteners from McMaster-Carr to connect the rotary encoders to the garage door shafts.

I ordered a Netgear ProSAFE JGS516PE 16-Port Gigabit Rackmount PoE switch with 8 PoE ports (85w total). I’ve been needing a PoE switch for a while, since I want to install a couple of PoE IP cameras. I also ordered 1000′ of yellow Cat5e cable to use for PoE applications. This will make it easy to identify ethernet cables that have PoE in my home, since my others are blue, grey or white. Finally, I ordered a PoE splitter with 5V microUSB output to power the Raspberry Pi.

In my spare time, I’ve been working on a Raspberry Pi garage door opener project.

The main goal is the ability to open or close my garage door from my iPhone or CarPlay. Unlike the existing projects I’ve seen, my solution has a rotary encoder on each door in addition to a door closed switch. The rotary encoders allow me to see if the door is moving, and hence close or open the door with a single button press. i.e. instead of a direction-ignorant ‘Activate’ button, I can have separate ‘Open’ and ‘Close’ buttons that will do the right thing, even if the door initially moves in the wrong direction. And I can handle two doors with one Raspberry Pi. I could handle more, but I only need it to handle two doors.

Unlike some of the commercial solutions, my solution does not require cloud services. It will still work when my Internet connection is down. If I’m in WiFi range with my phone, I can open and close my garage doors. If my Internet connection is up, I’ll be able to do the same from anywhere in the world.

It is more secure than the average IoT solution. The authentication protocol uses 2048-bit RSA as the base encryption, over which I send an AES256-encrypted randomly generated challenge. The client must decrypt the challenge using their private RSA key, then decrypt the AES256-encrypted challenge with the shared secret key, then encrypt with my server’s public key and send the challenge response. Post-authentication, the session uses AES256. Sessions will typically be short-lived, and we never exchange any secrets. The server will automatically generate a new 2048-bit RSA key each week, which should eliminate the ability of anyone being able to crack the public key crypto and use it in my lifetime (I don’t see a usable quantum computer on the horizon, and the NSA would just break my door down instead of cracking my garage door opener).

I’m nearly done with the server side that runs on the Raspberry Pi. I’m running FreeBSD 11 on the Raspberry Pi, and my server is multithreaded in order to be able to monitor all of the sensors and be responsive to clients at the same time. It is written in modern C++ since that’s been my server language of choice for… 18 years? All unit tests are done for the code that is completed, and I have tested the server with a simple client. I have also tested the sensor inputs, but I’ve yet to send out my piggyback I/O board design for manufacturing. The industrial rotary encoders will arrive soon, so I’ll probably order my PCBs sometime in the next few weeks.

In order to make the iOS side of things easier, client/server messages are encapsulated in JSON. Since I’m using jsoncpp on the server side, it’s trivial for me to write a Qt app for the desktop and a Wt app for my web server if desired since I’d just use jsoncopp in these cases.

Crypto is still ugly to do with Swift, but I’ll manage. I’m going to try to keep my Objective-C and other non-Swift code to a minimum on the iOS side of things.

I intend to allow configuration from a client. The server code to support this is not complete, but the protocol work is in place.

Probably worth noting that I created a separate libDwmAuth project so I can reuse the authentication and encryption in other IoT projects. No cloud needed, no clear text flying around my wired or wireless networks.