LinkMeter v2 Homebrew BBQ Controller - Part 1


 
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Bryan Mayland

Bryan Mayland

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Continuing from the origianl LinkMeter thread to avoid confusion of "Research and Development" information.

LinkMeter is an OpenWrt firmware / package for interfacing to a HeaterMeter Arduino / ATmega328 based automatic BBQ controller. The fusion allows the HeaterMeter to control the grill temperature, while passing the heavy lifting of WiFi access and data storage off to the OpenWrt-compatible router. A more concise description can be found in An Introduction to LinkMeter & HeaterMeter

LinkMeter Home Screen
linkmeter-2011081001.png


Project Page - GitHub Hosting
LinkMeter is an open source project and is hosted on my GitHub page. The ultimate source for information is the HeaterMeter Project Wiki which I will flesh out as we go.

Hardware
The official HeaterMeter board schematic and parts list is in the GitHub wiki. Do not use the schematic from the git repository eagle directory unless you understand it may be an experimental build depending on when you pull it. The official version linked from the wiki is generally what you need.

linkmeter-2011050707.JPG


As you can tell the preferred platform is the Linksys WRT54GL router. A rough outline of the required steps to build a LinkMeter
1) Build a HeaterMeter-for-LinkMeter ATmega328 board. IMPORTANT while you can use the HeaterMeter design from the standalone HeaterMeter schematic posted in the other thread, the official schematic from GitHub has additional components to support additional functionality, as well as being designed to fit inside the WRT54GL case. The official new schematic can also be used in a standalone fashion.

2) Flash the HeaterMeter with the arduino/heatermeter firmware. This can be done with a USBtinyISP, another Arduino, or any other ICSP programmer you might have.

3) Flash your WRT54GL with a prebuilt LinkMeter firmware image. Snapshot recommended image. The packages are pre-installed and are only supplied for users wishing to install them on their own firmware.

4) Connect the HeaterMeter to your router via the internal serial port.

5) Plug your computer directly into one of the LAN ports. You will be assigned a network address (DHCP) in the 192.168.200.x range. Configure your wireless settings using the web interface at http://192.168.200.1/. Generally, you want your wireless to be configured in Client mode (aka station mode) on your existing wireless network and to use DHCP.

6) Configure your probes depending on your build and probe types. (More information here soon)

7) BBQ

Premade PCBs
Current revision is v3.2. I use Dorkbot PDX to create the boards using the LinkMeter HM cam output and they will provide 3 boards for ~$28 shipped. Because you get 3 and you only need one, you'll probably have extras. If you have extras or need one post and let us know and I'll try to keep this list up to date:
 
Originally posted by Brian Hilgert:
Bryan, is it worth it for those of us running previous releases to upgrade?
Click to expand...
Oh good question. The LinkMeter-specific web pages load about twice as fast (give or take), aaand you can click on and off the various lines on the graph. So if those features tickle your fancy, there are instructions on the v1 to v2 wiki page.
 
Just sent my first ever PCB design out to be created. I've got my fingers crossed that in 2 weeks this design works:
8P4A8.png


The RFM12B wireless board is completely optional and can be left out to save $8 or so on the build cost. Also note that there is either a 2.1mm barrel jack or a pinheader power input. This means you can use this same PCB to build a straight HeaterMeter board or put it inside the WRT54GL. The dimensions are 2.4"x2.0". I will almost certainly have updates to this, probably changing it to 2.6"x1.8".

Also hats off to Ed, whose board I am even more in awe of considering how he managed to fit all of this on a one sided board with just a few jumper wires. Also that he managed to make his silkscreen layers not look like complete garbage and actually have the tNames in the right place.
 
Looking forward to this. I was about to bite the bullet and try to build it on perf-board, but if a PCB is potentially only a couple weeks away, I think I can wait.
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Does the LinkMeter have a JSON or XML feed of the data for easy manipulation outside of the built-in pages?
 
Originally posted by Ben Fillmore:
Does the LinkMeter have a JSON or XML feed of the data for easy manipulation outside of the built-in pages?
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Yeah you can still get the json from /luci/lm/json and you can get a CSV-style dump of all the data from /luci/lm/hist

As for the circuit board, yeah I hope it works. I'd have to say it would be a miracle if my first ever PCB design would work first try though.
 
Originally posted by RJ Riememsnider:
Very nice Bryan! How many boards did you order, is there a minimum? Any plans to sell them?
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I got the standard 3 boards from Dorkbot and I already know there's one problem with them which can be fixed with a jumper wire. I'd also like to add a standard 5 pin FTDI cable header while I'm at it.

I've actually been informed of another place (the name of which escapes me at the moment) that will do up to ten 10cmx10cm boards for $25. I don't know if they charge a setup fee or shipping though. I doubt I'll be selling them (except for any working prototypes) but I'll be making the schematic and board EAGLE files available via github.
 
Ill keep an eye open for your schematic and Eagle files as I'd like to build this but don't really want to breadboard it...my thoughts if you make it do it nice looking!
 
WOW ! Great work on your documentation threads and packaging this in the Linksys case. I would suggest using a freezer bag to waterproof it.
 
Originally posted by Ed Pinnell:
1.) Am I the only one (outside of Bryan) trying to use R2? It doesn't appear to work "out of the box", but it might just be me. Is anyone else using R2?
2.) Bryan, does R2 represent the future of the LinkMeter, or will both versions be supported?
3.) Is the Arduino code the same, now and in the forseeable future, for R1 and R2? I notice you've posted a .hex file for R2 but not R1.
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Welcome back Ed! Good to see you again and I hope you enjoyed your time away from home (when you weren't going back to do laundry)

1) I use R2! It doesn't work out of the box? What doesn't work? I tried to test it thoroughly and even wiped my router and reinstalled it from scratch.
2) R2 is V2 is the second release. It is just a "checkpoint" for people who don't want to build their own firmwares-- a build that (at least was supposed to) work right out of the box.
3) The code evolves. Backward hardware compatibility is maintained, but software may or may not be compatible. If they are compatible, it is only coincidental. R2 router firmware goes with R2 arduino firmware. I didn't have a a hex file for the V1 because I'm not exactly sure where it is in the source tree. There are some differences to the serial protocol between 1 and 2 though so some things won't work properly if you mix and match.
 
Originally posted by D Peart:
http://tvwbb.com/eve/forums/a/...931090216#4931090216

Is that the correct one?
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As Ed said, I'll confirm. Both are currently inaccurate. I'm waiting to get my boards in the mail to test out the new design. As soon as I have a working design I will post a full schematic, board design, parts list, supplier links.

The board can be used as standard non-wifi non-RF HeaterMeter, creating an easy-to-assemble LCD+Buttons temperature controller for something on the order of maybe $60-$70 (probes excluded).

The board can also be built for going inside a LinkMeter with or without RF probe nodes.

Because of the 3 configurations, there's a lot of optional parts so the parts list will also reflect this. Hold on, should just be another week or two!
 
I can wait, it'll be hard but I can do it
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Is it possible to control two pits at once? Not sure what the rf module adds. Does it add two temp and a pit probe?



Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
http://tvwbb.com/eve/forums/a/...931090216#4931090216

Is that the correct one?
Click to expand...
As Ed said, I'll confirm. Both are currently inaccurate. I'm waiting to get my boards in the mail to test out the new design. As soon as I have a working design I will post a full schematic, board design, parts list, supplier links.

The board can be used as standard non-wifi non-RF HeaterMeter, creating an easy-to-assemble LCD+Buttons temperature controller for something on the order of maybe $60-$70 (probes excluded).

The board can also be built for going inside a LinkMeter with or without RF probe nodes.

Because of the 3 configurations, there's a lot of optional parts so the parts list will also reflect this. Hold on, should just be another week or two! </div></BLOCKQUOTE>
 
Originally posted by Ed Pinnell:
EDIT: Well, that didn't work, either...it froze again about an hour ago, after running for nearly 4 hours. I'll get back to you on R2, but I'd still like to know if anyone else is using it. I learn so much more when I try to solve my own problems.
Click to expand...

Ed how did it freeze? Did the Atmega freeze? or did it just stop graphing?

The reason I ask mine too would freeze and I had to hit the reset button on the board, after I got ther bigger blower. It would look just fine looking at the graphing on the net but it would be froozen at the time the atmega would freeze.

The only thing that fixed it, was getting rid of the IRL510. I have not had a single freeze(lock up) since then. That maybe a ok part but it was not in my case.
 
Originally posted by D Peart:
Is it possible to control two pits at once? Not sure what the rf module adds. Does it add two temp and a pit probe?
Click to expand...
No it is still limited to one pit. The RF module allows you to have any of the 4 probes be in one or more LinkMeter Remote modules. It is just simple ATmega + RFM12B that transmits back its probe data to the LinkMeter to replace the internal probes. The idea being if you have something that you can't run a wire to (e.g. a rotisserie) you can use a wireless node to monitor the temperature there.

Ed: Are you getting router lockups? Is this on the device you've increased the memory on? You might want to try checking your /etc/config/lucid and check the main section for "option 'threadlimit'". It should have been set to 2 by the install but lowering it to 1 might be a fix if you're running out of memory.

You can also check it from the serial cable on ttyS0 I believe. If you're running out of memory you'll see the kernel invoking the "oom-killer" which dumps a crapton of information.
 
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