Back to the Original Purpose

Enough with the SDRs and Chumby's and other distractions. Well, mostly...

I've been a subscriber to EE Times for probably 20 years. It used to be a weekly paper like format, but is now a skinny magazine, but with amazing web bits to supplement it. A couple weeks ago, there was the an invitation to a webinar on RTD and Thermocouples put on by Maxim. The webinar happened on Wednesday, and I listened to it. Pretty good talk, the speaker couple have been more exciting, but was well prepared, and talked about some good products. He didn't convince me to switch to RTD's but I am now thinking of using an integrated SPI chip to do everything.

The webinar hammered into me the reason for the second temperature sensor at the cold junction. The reason is, that ends up being a second thermocouple, since the copper wires that we are connecting to are of different material than the wires in the thermocouple. If we don't know that temperature, then the actual temperature we want to measure will be off a bit. Having the second temperature sensor will add to the complexity, and cost of the circuit.

The one complex circuit presented used the MAX6126 for voltage reference, and DS600 for the cold junction temperature sensor and the MX7705 for A/D converter. There was some discussion about keeping a constant current source, and other details using these three chips to get a good measuring circuit.

Then he showed the MAX31855, wow, pretty simple. Connect the thermocouple on two pins, some power on a couple more pins, a crystal and capacitors on other pins, and then the SPI to the processor and you are done! About the simplest convertor I have seen for under $5! It does SPI, so I should be able to piggyback 8 or 12 or 16 depending on engine chosen. I won't have to use up the A/D convertors to get past a 6 cylinder engine. There is an SPI library for the Arduino and everything.

Now I am still dreaming, I need to actually build something. I need to order about 8 of them, 4 J type, and 4 K type. DigiKey has them for about $3.55 each, but only if you order 2500 at a time! Single quantities are over $7.50 each, and hard to come by. Maxim is generous, and offers them as free samples. I was able to get 2 of each that way. Well, I ordered them tonight. They are just up the street, well some part of the company is (right down Beltline on Midway in Addison, probably 5 miles west, yup google maps says 4.7 miles).

Another toy

This is sort of related, since it is Android. I got an Mk808 android device. I say device, because I am not sure how to categorize it. It plugs into a HDMI port on a TV or monitor and uses that for a display. Otherwise it mostly acts like a tablet processor. There are no g sensors or touch screens, but you can plug in mice (or bluetooth mice) and control the desktop that way. It can run crackle or netflix, and youtube so it is good for an entertainment device. It has a browser (two), and can read and write office like documents (or use google docs).

So what you say, I can get a tablet and do all that. How about replacing your PC with one of these? What would it hurt? You say you can't download photos to it, no you probably can't. You can't play games on it? Well, my kids are driving my wife nuts playing angry birds. You can download all kinds of games. It has the whole google play store on it. Games, apps and media are all available.

What if you wrote desktop type apps for it. Why not, you know, a 32 in 1080p monitor would be way cooler than two 20 inchers, there would be no line, and the mouse would smoothly slide between windows.

What does a desktop PC cost, $400, maybe $1000? Well this is under $100. Yes, that is right, 1.6GHz processor with 1GB memory isn't much, but it might be worth a try? EBay has 'em for about $50 if you want to experiment and don't want to blow too much. Get one of the fancy wireless keyboard mouse combos and you have a full multimedia center. Cut the cable and do some fun stuff.

Chumby Links, and Tips

People are starting to ask me questions about the Chumby. I am not sure what to think, but rather than getting asked the same questions dozens of times, I thought I'd offer some answers ahead of time.

How did I load my software?

You can start up an SSHD on the Chumby. Go to the about device screen in setup and click on the pi symbol in the upper right corner. Using something like putty on windows, or ssh on linux/mac command line, you can connect as the root user. On my chumby, I connect by typing:

   ssh root@192.168.2.10

or
   ssh 192.168.2.10 -l root

By default there is no password. You can add one, but on reboot, the sshd turns off, and no one can connect. There are instructions for adding passwords on chumby tricks web site. Actually that page has lots of useful links.

I am an emacs user. It is a wonderful tool/IDE/editor. There is no emacs on the stock chumby. I used my laptop to enter the code, this provided me a place to backup the code, so now it is on both the Chumby and my PC. I then cut-n-pasted to a simple vi session on the chumby.

Of course Perl is already there, and all I needed to do was write some code it could interpret. Yes, interpret, but trust me, well written Perl is stinking fast. I've done some image processing using it, it is fast enough.

Where did I store my app?

There is a micro SD card in the Chumby. It can be removed, and I imagine you could load your code on there. You don't need to, you can use the read write file system /mnt/storage to put your code on. I made a sub directory and called it bin, to be standard with the rest of *nix. (If you want to learn about the philosophy behind Unix/Linux etc, the book The UNIX Programming Environment by Kernighan and Pike, read it study it, and you will be the best programmer ever).

How to start the app?

Every time the Chumby boots up, or any *nix system starts, it runs some fixed sequence. There are some scripts in /etc/init.d that has the scripts. I didn't use them, because that partition is read only. You can do a mount -o remount,rw / on that partition, and put in your script. 

I did it the old fashion way; using the command line. Unix is funny, if you start an app on the command line, and the terminal that that app was started from the app goes away also. There are things we can do to get around that. The nohup command is how we ignore the hangup signal when the terminal goes away. Just start the program prefixing the command line with "nohup" and end it with an ampersand "&", and the program will keep running until it gets a fatal error, or the computer reboots.

Another way to make an app keep running after the terminal goes away, involves fork and exec, and a disoconnect. The Stevens book Advanced Programming in the Unix Environment (another book you should be at least familiar with if you want to be a great programmer) has that answer.

Sending Mail 

Oh boy, how does mail work. The chumby acts as a client to a mail server. The mail server is usually called the "SMTP" (Simple Mail Transport Protocol) server. Your ISP probably has a SMTP server that you can use, or google users can use the Google one. The sendmail program on the chumby is the client program that talks to the SMTP server program. The SMTP server will help route your message to the appropriate next hop on the way to the mails destination.

SMTP servers have many options. Some require authentication, some don't. You will have to read all your server documentation to figure out what kind of authentication (if any) is needed. Sendmail can handle most, maybe not in the orientation you are thinking. Like sometimes you need the ssh port, other times it will leave everything visible.

There is some documentation about connecting to gmail at:

     http://forums.fengoffice.com/index.php?topic=190.10;wap2


If it isn't working, run the sendmail command using the strace. Something like:

   strace sendmail cozytom@gmail.com -f sender@example.com  -S smtp-server.tx.rr.com -au senderusername -ap senderpassword < mail.txt

The output will be pretty chatty, but you should be able to see any errors or find clues as to where it is quitting. 


There is probably more to consider, but that will get you started anyway.

 
 

Don't Try This at Home

It isn't dangerous, or anything, mostly just dumb. I wanted a way to know my garage got shut, after I left. Sometimes things happen, and the door doesn't shut all the way, maybe something fell while it was closing, or maybe a cat ran in or out. The optical sensors pick it up, and think it is a kid, so it reverses. I didn't always wait for the door to close, before driving away, then two blocks away, I wonder, did it close.

I used to be really interested in home automation. My previous house had most of the lights controlled by X-10. I had a Unix computer as the hub, allowing a bridge from the X10 to cron jobs, other sensors, and sprinkler controllers. I could be out on my deck, and press a button on the X-10 remote to start a sprinkler. I could turn off the sprinklers by pressing a code on the phone. The Unix machine was a Sun 3/110, mostly because it had a VME serial board, allowing 10 serial ports. The bedroom had a light that would start out low, and get brighter minute by minute, for my morning wake up. It was fun, and I tried to sell this stuff for a while.

My  Plan

I know Craftsman has a garage door opener that will talk to your smart phone and let you know the state of the door. I thought, maybe it was an add on to any craftsman or other garage door, but it wasn't so. It is only available with the specific assure link models. Thinking what I would pay for such a thing, maybe I'd be willing to go $60. The AssureLink also has an annual fee.

I thought if there was a simple board, that had some GPIO, and a WiFi link, for about $50 that would be perfect. I thought maybe there would be some ARM or Pic chip based board that would be perfect. I couldn't find one, not standalone.

To get the message to a smart phone, I thought I'd be able to use one of the free email systems, maybe use an address like tomsgarage@gmail.com or something. The smart phone would be able to subscribe to that address, and I'd know the state of the door. When the door changed states, an email would be sent out.

I asked the DPRG group about such a plan, and got a few ideas. Folks offered suggestions, but eventually what I did find was a Chumby clone, the Best Buy branded Insignia Infocast, on eBay for about $35.

The process

I got on eBay, and someone had an actual Chumby, for under $20. A closer look showed it came without a power supply. Well, it is open source hardware and software, what can be so hard about getting a power supply for it. I bid on it. Then I started looking for a power supply. Ooops, the official Chumby power supplies are $15-20 on eBay. So much for saving money, I guess I don't need the official power supply, I can use the bench supply until I can source something else. hmmmmm.....

Ok, I am still under $50, let me look around. Sure enough, I found an Insignia Infocast for about $30 so I ordered it. The chumby came, and I messed with it. Dang, my simple power supply didn't have enough current. The diagram says 2.5A, wow! This isn't a green project anymore (that is a few watts). Finally the Infocast showed up with it's power supply. Cool it works for both the Chumby and the infocast.

My kids then stole it. If you don't know what the chumby is, it is pretty cool. A little 3.5 inch LCD touch screen (resistive), and ARM processor (400MHz or something). It is Linux based, and uses webkit for the Gui. You need to be registered to get apps are for it. There are some apps that come with it, including radios both software (IE Pandora) and a true FM receiver.  Most of the inside of the case is dedicated to giving the little speaker sound good! It isn't bad, and would make an excellent bedroom alarm clock.  The kids loved the radio, I didn't try to explain Pandora or any of that back.

Eventually I was able to steal it back. I kind like it, using it for a radio, and I could see it useful for other stuff, so I didn't want to break it.

A little work with the soldering iron, and I got a ribbon cable connected to the GPIO port. I didn't think a connector would fit. The main LCD cable goes right across the GPIO port (connector for the LCD ribbon is the upper right corner).

I used to solder ribbon cables all the time. I did a bunch of keyboards when I had the old Xerox 820, and the serial cables before I found the press on ones, so I got the technique. How about this:

I thought, I'd keep things simple. I knew to control a switch, I needed ground, thinking that the GPIO pin would float high, and then I thought I would help the pin float high with a pull up. The schematic ended up being something like:

The control pin is that middle pin D3, the one across from the GND, keeping the wiring simple. +3V is on the end. I got a magnetic reed switch, like used for alarms for the switch. The magnet was stuck to the side of the door.

The Software

 I was surprised, someone said just use GCC. Nothing to it, right, I use it everyday, there are instructions to download gcc and program the chumby natively. It didn't work, not sure if the chumby folks gave up on it, or I did it wrong. I noticed there was a perl interpreter included. Why not, this won't be very complicated, read a single pin, when the state changes.

I used regutils command to read the pin. And sendmail to send the mail out. It isn't fancy, or efficient, just something that will run in the background, tests the one pin once a second. here is the code:

#!/usr/bin/perl
#
#  setup the chumby for reading, and read pin3.
#
#  tgb 10-20-12
#

## setup IO
`regutil -w HW_PINCTRL_MUXSEL0_SET=0x00000003`;

my $curVal="";
my $newVal="";
my $results;
my $ccmp;
my $val;


while (true) {
    $result = `regutil -r HW_PINCTRL_DIN0`;
    chomp($result);
    $result =~ m/Value at.*: (.*)/i;
    $ccmp = $1;
    $val = hex $ccmp;

    print " CMP 00 ".$ccmp." 11 $val ";

    if ($val & 0x08) {
    $newVal = "CLOSED";
    } else {
    $newVal =  "OPEN";
    }

    print "$newVal\r";
    if ($newVal ne $curVal) {
    sendmsg($newVal);
    $curVal = $newVal;
    }
    sleep 1;
}

sub sendmsg
{
    my $msg = shift;

    #sendmail cozytom@gmail.com -f sender@example.com  -S smtp-server.tx.rr.com -au senderusername -ap senderpassword < mail.txt

    open MAILFILE,"> /tmp/mail.txt";
    print MAILFILE "from: cozytom@tx.rr.com\n";
    print MAILFILE "subject: garagedoor $msg\n";
    print MAILFILE "Garage is $msg\n";
    close MAILFILE;

    `sendmail yourgarage\@gmail.com -f "me@email.com"  -S smtp-server.yourdomain.com < /tmp/mail.txt`
}

Why did I do this

Which part, do the actual project? Well that I discussed already. Wanted to know the state of my garage door. How about, why publish it. Well, I needed to show folks I actually am able to accomplish something. Yes this works, I finally completed something. Once I get around to collecting all the parts I am able to make it work.

What was dumb? Well 2.5A for a silly monitor system. It is much better than the silly Sun 3/110. It isn't doing X-10, or anything, but it doesn't need to. I still have a radio and other uses in the garage for it. Probably no one else will use it, but maybe it will inspire someone to do something similar.

Good Luck

I am trying get fire myself up

I've sadly been neglecting this. Life is busy again, or still, or whatever. Shoot, I'd love to have a couple hours a day to work on this, but I don't. Between kids and homework, normal home repairs and other distractions, I haven't been too consistent.

SDR

I did get the SDR receiver, and I played with it. Not sure if it is the antenna, or what, but it only kinda works. It works well enough that I can say the vendors charging more than $100 for a UAT or 1090ES ADS-B in are charging too much. Here is another blogger working on the same idea: http://www.sharebrained.com/2012/05/10/progress-on-my-sdr/ 

Why do you want an ADS-B only receiver? Not only can you see where the other planes are, but FIS-B will give you weather, and NOTAMS and other good info. It is all broadcast the same way, and it is free to everyone in the air. (XM might be in trouble).

Arduino

Holy cow, people who did know about open source stuff are suddenly finding out about Arduino's and wanting to put them in airplanes. They can be very useful, with the UAV autopilot stuff, and IMUs and all. Lots can be done, we just have to get to it. There are ARM boards that will host the Arduino shields, and developer software coming soon, so you can have even more power, for only a little money (less than $100).

IMUs 

There have been lots of IMUs around for a little while. Some better than others, and most aimed at the RC plane market. STM is coming out with a dev board that has all the hardware for an IMU. Developer market is all they are shooting for, but the board is supposed to be about $10! http://www.st.com/internet/com/press_release/p3323.jsp . Maybe they will be available by Halloween, and I'll have yet another distraction.

stuff

I had a spike in viewers this week. That is good I guess. Maybe eventually all of what I've built will generate enough traffic to pay for some of this stuff.

Write Soon!

Another Distraction

Of course last weekend was the holiday, and this week was full of adventure. I got to ride a new airplane up to Chicago (new for the airline, not new to the world). It was full of employees, so the rules were a little relaxed. Everyone was taking pictures, and the cockpit door was open the whole flight. Really fun for that part of the flight. I had to make my own way home, so that was frustrating and all the normal fun of non-revenue travel.

I ordered a EZ430 Chronos about a week ago. I needed a watch anyway, but this was too good a deal on tideals.com. $25 for the whole kit. That showed up when I got home from my trip to Chicago. Been using it as a watch for the week, but last night I tried to get the development environment going. Well the laptop has shut me down again....

The CCSv4 needs to run in eclipse. Guess what, it didn't install again. I rolled back to helios from indigo, and that was no help. I am so frustrated with this laptop, probably vista, but who knows. I'll probably go ahead and load everything on the desktop, and it'll work.

I did load eagleCAD on the laptop while waiting for a flight in Chicago, and started getting the schematic drawn. Ran out of time, and still haven't finished that. Maybe I'll have some time next week.

Stay in touch.

Android vs iPad

Uh Oh, religion...

Well, to some people what I am talking about is heresy. Forgive me, and listen. Both Apple and Android make fine tablets for different purposes. Actually, for the common use, both are probably equal. Maybe for watching movies on a portable device, the new iPad is better. For word processing, I don't think either is suitable for long term use, but for occasional, they each are probably equal.

We aren't watching movies or word processing. We are trying to monitor something. Does a retina display help that? Not really.

The place where the iPad completely fails is in Bluetooth profiles. The iPad comes out of the box without the serial port profile (SPP). Apple rightfully says you don't need it. Not to watch movies, answer email, play angry birds or word processing. You can add it, but that is a challenge. The are things like the BlueSnap Bridge, but at best I'd call that a kludge. It only sends ASCII, no problem, but it is another box to maintain (battery charge, etc).

The Android has SPP as a standard. Many people realize this is a huge feature of the android, and are building their products to take advantage of this. There are automotive engine monitors that will do this today, and won't support iOS because of the lack of SPP.

So you say "all the aviation companies support iPads". That is true, to an extent. Certainly Jeppesen, WingX and others support iPads. WingX also supports Android, and there is a whole site dedicated to Android aviation apps. Flightplan.com, flightaware.com and others also have nice Android apps.

How about form factor. Say you have a big panel, and you want to fill it with tablets. No problem, get a couple 10 in displays, and you are good. How about a small panel, maybe 2 7inchers, and a 4inch for backup. But you say iPads only come in one size, how do they compete? (you might be noticing a pattern).

Then the argument about the enterprise. iPads work great in the enterprise, they sync email and scheduling. Okey doke, but not a 10,000 over eastern Montana they don't. You want to sync with your engine, and maybe your air data computer. That is what matters. If you need to sync with your office, you'll  need a data connection to the ground (row44 maybe?). By the way, Androids' sync to email and scheduling just as well.


Licensing and releases, well the android probably will win that. Apple comes along and thinks what is best for iTunes, not your charts. Remember the iOS4 trouble when the iOS would clean up your "old" files for you, thinking they were old movies or songs. That low altitude enroute chart that was 25 days old didn't survive, and you had to scramble to find a sectional or high altitude chart to cover for you. You can vette out the system that works for you, and take or not upgrades for your display.

How about RIM or Windows. Maybe, they will work. I still haven't seen a windows tablet, and the PlayBook is only available in one size. If someone has time, we could work on it together (you want to send me one, I'll play with it, I promise :-). Critical mass is the magic here, are they available, can I get one, and what do I need to develop for it?

The SDK for the iPad and Android seem to cost about the same thing, nothing. Writing for the iPad is in Objective-C. The Android is Java sorta. Both languages are object oriented, with a C base. There are many people in the world who can develop for them, so that wouldn't be a reason to pick one over the other. Apple tends to control the iTunes store, and that is about the only way to deliver apps to the iPad. Android allows others to host and distribute apps, you aren't locked in to the Android market. There are risks getting apps from a non-android or non-apple market, but most are honest, so they work. There are malicious apps in both market places, and they get cleaned up fairly quickly.

For me, I have chosen the Android eco-system because of the openness, or at least appearance of openness. I havn't spent a dime on software, I have a demo cooking, and it'll work with my stuff as I designed it. Your mileage may vary, and I'll listen to any argument.

Keep on soldering.

Another SDR Post

I started putting together the hardware for the thermocouple amplifiers, but quickly realized I didn't have everything I needed. I needed some reasonable sized capacitors (0.47uf 10V or so) and a trimmer resistor. The closest I could find in my collection was a .10uf at 25V or .33uf at 1000V. I thought, crap, for less than a dollar, I should get what I need. That 1000V cap, while close to what I needed, was bigger than the chip. Board real-estate would be a challenge.  I know it is just a proof of concept, but I needed something better. I have some surface mount caps, but even those were all over the map, like 47uf, or 100pf, nothing kinda medium.

I was thinking a quick order at Mouser or Digi-Key and I would have what I need by Wednesday. Well, it would take a $25 minimum order, and I'd obsess over what else to buy for 5 days, and I wouldn't get what I need until next week. I had a coincidence happen on Tuesday. Traffic was awful, and I needed to try a different way home. I ended up in Farmers Branch. Tanners Electronics is right there. I thought I am close, maybe they stay open until 6pm. IT was about 4:50pm, and I was close, so I thought I'd go for it.

They are open until 6 Monday through Saturday. I could pop in there and get what I needed. When I got there, I was surprised. They had about the same collection of small capacitors as I did, .33uf at 1000V and some surface mount ones. I did find a couple medium ones, one disk, and one film and a small one, mylar I think. I bought an assortment, at least 2 of each, and a couple trimmer pots, spending all of $3, and I had them.

I haven't had time to do anything with them though. I hope to this weekend.

I've been thinking what a full system might look like. How about the Arduino as the engine controller and monitor. This is for the full FADEC system. Then a USB connection to a central hub, maybe an ARM controller running Linux. Another Arduino running DIY Drone air data computer, and IRS gyro package connected to the central controller over USB. Each Arduino would have their own blue tooth connection for sending to the display computers. Display computers would be Android tablets. I am not sure what the central system would do other than data collection. I guess it should share information, with the two Arduino's. Like putting in a TOGA button, the FADEC would run the engine up for takeoff power, then the autopilot would fly the missed approach procedure. The central computer would have some GPS and mapping software, unless that was outboard also (Android tablet may have that?).

Lots of planning and dreaming.

I said this was an SDR post. Well, here is the SDR info. Suddenly SDR hardware is down to about $20! You can buy USB tuner cards for PC's that have untuned front ends for $15-25 on EBay. There is software available to use them, and they are quite popular. They can tune anything from about 64-1700MHz and should work in almost any mode (even TV, since that is what they are designed for!). Reddit has a hardware compatibility chart. 

I ordered one, maybe, I'll have time to play with it. It sounds like it has most of the software written. All I need to do is plug it in and run some code.

I also found the LinuxCNC website. That might be my answer to the 3D printer I've been wanting to work on. Again, when I get some time, I'll take another look at it.