brainwagon "There is much pleasure in useless knowledge." — Bertrand Russell

6Feb/162

New experiment… Life beyond Comcast…

Today, I finally lost my freaking mind with respect to Comcast.

First of all, some background. I've have been a Comcast customer since 1999 when I moved into my house. For the most part, the service itself has been reasonably reliable and effective. I don't have a lot of technical quibbles with them.

But their customer service makes me absolutely insane.

I am currently paying $269 a month (yeah, I know, right?) for a combination of Internet, TV, and phone (which I didn't even want, but which was part of some "package" deal that was supposed to save me lots of money, that somehow never really materialized). I have mostly been ignoring it, but I finally decided that if I am paying nearly $3000 a year on television and Internet, I should review my priorities to reduce my bill since I pay for a lot of premium services that I probably don't really need.

And here is where my irritation begins.

Because if you want to do that, you can't do it online. In fact, other than determining that someone, somewhere signed me up for some package which has the label "HD XF Premier Bundle" and a somewhat mysterious "Additional Outlet Fee" for $39.00, it has no indication about what Internet speed limits can be be achieved, what channels are included or not included, and most importantly there is no way to actually determine what my options are. In fact, to make any changes to your service, that means talking to a service representative.

And here is where my absolute rage begins.

I hate losing my temper with people. I really do. I like to be easy going and polite. If someone is trying to help me, I try to help them help me. But Comcast service representatives are not there to help you. They are there to sell their package deals, which seem carefully constructed to be as opaque as humanly possible and to extract the maximum amount of money from you that they possibly can.

It's infuriating, and today my fuse was admittedly short.

To be fair, I probably wasn't fair. I wanted to a) review each of the charges on my bill and b) decide in each case whether the charge was appropriate, and what my options might be to change it. But the Comcast service representative literally could not do that. She insisted on trying to tell me that there was some other package, with some other price that she could sign me up for that would achieve some other price that was much cheaper. When I said that sounded better, she asked me whether I wanted to sign up for a "commitment" or not, and started explaining that if I signed up for a commitment, then I could not change my service for two years. And I am supposed to decide all of this without an actual itemization of the terms and conditions or even the services that were provided.

And I lost my freaking mind. Expletives were emitted. I was not a gentlemen. And then something that has never happened before, happened.

I had a customer service representative hang up on me.

So, I'm going to do something truly crazy: I'm ditching Comcast. Sonic.net has become available in my neighborhood, and they have more sensible packages available with Direct TV. I imagine that the service that I am going to get is a bit less speedy than Comcast, but I literally don't care. I literally don't care if Direct TV is better or worse than Comcast or even cheaper. I just no longer want to be a Comcast customer, and since it appears I don't have to, I am not going to.

Voting with my feet. I'll let you all know how it goes.

Filed under: Amateur Radio 2 Comments
7Jun/150

An Arduino Powered HF Beacon…

LB3RE sent me a link to this awesome HF beacon by Anthony, F4GOH and Christophe, F4GOJ that has many of the same features as my (as yet still in-progress) beacon transmitter does. And, of course, his actually exists, so it's already infinitely more awesome than my idea.

I was particularly interested in his very simple power amplifier using 4 ganged BS170s. I'm likely to be operating mostly on 30m, so I think I could probably get buy with a single harmonic filter, and I am not imagining that I need all the relay switching, but there is some good information to be mined in there.

31May/150

Some reliability problems with my DS3231…

I was working on some additional software to power my nascent WSPR project. I've been thinking that rather than using an Arduino, it would be better to use the Teensy, so I've been experimenting a lot with the Teensy LC. My idea was to wire up my Ultimate GPS and an I2C based DS3231, and then write a sketch that powers up the GPS, attains a fix, and then uses the time to set the time on the DS3231. It then will periodically wake up the GPS and check the time as reported by the DS3231 against the GPS.

But I'm having some difficulty. The GPS part works just fine, but when I try to do the first write to the DS3231 to set the time, it occasionally hangs. The way these libraries are written, the writes never time out, and the exchange grinds to a halt.

I'm not sure what's going on here. Could be a bug/issue in the library, or something having to do with the Teensy Wire library, or the pull-ups. The rise times seem very slow.

graph2
I'll keep playing around to figure out what the deal is.

Addendum: This seems relevent but the code is only for real Arduinos, and probably needs some tweaks to work with the Teensy. I am curious as to whether the delay itself may be enough to help.

27May/151

Progress Report: Big Box O’ RF

Previously, I wrote about a project I called the Big Box O' RF. I've shifted goals a bit, and done some experimentation, and have changed some of my goals and approach.

First of all, I've changed the goal a bit. Instead of being a piece of test equipment, I'm actually more interested in using it to implement a beacon transmitter. It's been quite some time since I have done any QRSS (slow speed Morse) or WSPR (Weak Signal Propagation Reporter) but I still find it to be a pretty interesting thing to do. What I've wanted to have for a while was a dedicated beacon transmitter that didn't require the cooperation of my laptop and FT-817 to send out a modest signal. It seems to me that this totally doable mostly with parts I have on hand.

Goals:

  • Output power between 250mw and 500mw
  • Controlled by an inexpensive microcontroller. While the Arduino would be an obvious choice, the Teensy LC or Teensy 3.1 are as easy to program, and offer some interesting improvements for similar cost.
  • Able to integrate multiple methods to keep accurate type of time. Initial prototype will probably use the Ultimate GPS I've been playing with. Alternatives include clock boards based upon the DS1307 or DS3231, or synchronization via Wifi/SNTP (almost certainly using the ESP8266).
  • Able to support multiple modes: at least WSPR, DFCW, and Slow Feld.
  • LCD panel to display information. Text based interface supplied via USB, allowing you to change message, frequency, timing, etc...
  • RF generated by my AD9850 module.

I've been tinkering with most of the modules independently, making sure I can interface with each of them. They all seem to work fairly well. As soon as I find an appropriate box, I'll start getting them put together. I've built a harmonic filter for 30m (where I plan to do most of my operation). I need to work on the amplifier chain, as well as a little transmatch (I don't want to dedicate one of my antenna tuners to this operation either).

More to come soon.

26May/150

Teensy LC hooked to an Adafruit Ultimate GPS…

One of the things that I really like about the Teensy LC (besides its low price) is that it has three hardware serial ports. Hardware serial ports are just nicer than the SoftwareSerial ports that you see on the ordinary Arduino platform. While the latest support for SoftwareSerial ports on digital pins work reasonably well at low baud rates, they aren't especially good or reliable at higher baud rates. The Adafruit UltimateGPS I have supports data output at 10Hz, which requires serial rates of 115200, which isn't especially reliable.

But I'm still inexperienced with the Teensy. To test my understanding, I wrote this little program for the Teensy LC, after hooking my GPS up to pins 0/1 as RX/TX. Note: the Serial object does not route to any of these three outputs: the Serial object is a distinct USB object that is not mapped directly to digital pins.

This was also an attempt to test the TinyGPS library with the Teensy LC. It worked the very first time I got it to compile.

I'm definitely leaning toward using the Teensy (either the cheaper LC version, or the more expensive but more faster/more capable 3.1, which includes FIFOs for serial ports) on my WSPR project.

//   __                                        
//  / /____ ___ ___  ___ __ _________ ____  ___
// / __/ -_) -_) _ \(_-</ // /___/ _ `/ _ \(_-<
// \__/\__/\__/_//_/___/\_, /    \_, / .__/___/
//                     /___/    /___/_/        
//
// On the Teensy LC, there are three hardware supported serial ports.
//
// Port    Rx  Tx
// -------+--+--+
// Serial1| 0| 1|
// -------+--+--+
// Serial2| 9|10|
// -------+--+--+
// Serial3| 7| 8|
// -------+--+--+
//
// It appears (as yet unverified) that these are distinct from the serial
// port which is connected to the Serial object.  This program is designed
// to test that theory.

#include <TinyGPS.h>

TinyGPS gps;

void
setup()
{
    Serial.begin(9600);
    Serial1.begin(9600);
}

void
loop()
{
    unsigned long date, time, age;
    long lat, lng ;
    for (;;) {
        while (Serial1.available()) {
            char c = Serial1.read();
            if (gps.encode(c)) {
                gps.get_datetime(&date, &time, &age);
                Serial.print("Date: ");
                Serial.println(date);
                Serial.print("Time: ");
                Serial.println(time);
                gps.get_position(&lat, &lng) ;
                Serial.print("LAT: ");
                Serial.println(lat);
                Serial.print("LNG: ");
                Serial.println(lng);
                Serial.println();
            }
        }
    }
}
23May/150

Testing the DS3231 module… I’m impressed!

I hooked up my new DS3231 clock module to an Arduino that was being fed with the one pulse per second input from a locked GPS, and counted the number of pulses from each. In 3170 seconds, the clock module generated 103874565 pulses, for an average pulse per second of 32768.0015773 pulses per second. That's really good, only about 2 seconds per year. Of course this was a short term test, under relatively stable temperature conditions, but still, I'm highly impressed. I'm thinking that using this to drive my WSPR radio beacon is likely to work out very well.

17May/153

Weekend Update: Maker Faire, new gadgets, and I ground myself…

Greetings readers. I'm hopefully wishing there is still more than one.

This weekend was the Bay Area Maker Faire 2015, the 10th incarnation of an event which has become increasingly (even frighteningly) popular. I'm tempted to channel Yogi Berra, who said "Nobody goes there. It's way too crowded." Anyway, I got out of my house around 9:00AM, with the plan of parking at one of the offsite parking lots and shuttling in. It took me about an hour to get to the Oracle lot on 10 Twin Dolphin Drive, and there were already probably six or eight busses lined up, but probably a thousand people lined up as well. As it happens, it took slightly more than an hour to make it onto a shuttle, drive in and enter the gates. Bleh. Not the most fun, but I had a good nights sleep the night before, so I was mostly in good spirits as I entered the park.

It was very crowded. I was by myself, so I just started wandering. When I go to these things, I am mainly looking for three things:

  • Projects that inspire new projects.
  • Cool new products, especially inexpensive dev boards and gadgets for future projects.
  • Cool artwork that I haven't seen before.

Sadly, I didn't see a ton of projects that made me think of new projects, but there were a couple. I had a nice chat with Ben Krasnow who brought some low-tech versions of his excellent rheoscopic coffee table, which were just plastic cells that rotated on a lazy susan. You've probably seen identical gadgets in science museums. Fluid flow is always interesting. He said the instructions were already on the Make Magazine site, but I forgot to copy the url, and didn't find it. He also said it would be in the print edition sometime soon.

I had a nice chat with Erin Tomson of Modulo Labs LLC. She's a former Pixar colleague, who has gone off and created Modulo, a set of pluggable programmable modules that can be used to assemble modules in a tiny, secure network, without the hassle of routing jumper wires on breadboards. (In fact, a system like this would have prevented a lost hour of my time tonight, I'll tell that story below.) It's a very slick little system, and I'd like to see something like this take off. I can particularly see this as useful in education.

Check out her Kickstarter video.

I particularly like optical gadgets like telescopes and microscopes. My buddies Rich and Dave from the Chabot Telescope Makers Workshop were there, grinding away and answering questions about telescopes. Nice to catch up with them. They said that quite a few people came up to them and asked "So, you guys sell telescopes?" Sigh. This is the Maker Faire. If you are in the North Bay and want to learn how to build a telescope, click on the link above, and think about attending one of their free workshops (every Friday!).

I like projects which reuse camera phones, and this microscope project seemed pretty cool. They had a little gadget that allowed you to swap out three different lenses to get different magnifications. Their system seemed pretty cool, but the basic idea is pretty simple (in fact, it's basically a version of Antonie van Leeuwenhoek's first microscopes, but instead of holding it close to your eye, it's held close to your cell phone, which can use nifty features like zoom and exposure adjustments, and can of course record video and stills. I should design such a gadget myself.

I also had a nice chat with Alan Yates who was demonstrating some "Lighthouse" technology that he's been working on at Valve. The basic idea is to create a set of "beacons" that can be scattered around an environment, and a sensor that can (for instance) be mounted on a VR headset and can be used to figure out the position and orientation of the headset with high accuracy and low latency. I don't have a link for this work yet (did I miss it, Alan?) but when I do, I'll try to update it.

That was kind of it. I did poke my nose into various people experimenting with aquaponics, which I find interesting. I had a brief chat with the creators of Chip, the $9 computer currently on Kickstarter (I hope to have more information on that soon, stay tuned.) I didn't spend much time in the "Dark Room", the noise and flashing gives me a headache. I did spend some time looking at the various gardening and bee keeping exhibits.

And, I did pick up some new gadgets. Here's a short video of my purchases, along with some links to the various items mentioned.

And that's about it. If anyone thinks I missed something super cool, drop me a comment below and I'll check it out.

Today, I had a bunch of chores to do, but I did start to play around with my AD9850 project a bit more. Since I spent so much time driving around yesterday, I had lots of time to think, and realized that the code the determined the tuning word (the 32 bit value used to select the frequency of the oscillator) was probably going to not work properly, since it used floating point arithmetic, and that probably didn't have sufficient precision to do the calculation the way that I had coded. Indeed, when I got home, I hooked up and Arduino and found that I was not getting the sub-Hz spacing that I requested. I played around with the math a little bit, and got it working better, and then set it up and started it going. I had the output of the AD9850 going into my oscilloscope, so I could monitor the waveform.

And it was glitchy. Intermittent. Not working properly. Had I made a programming mistake?

I spent the better part of 45 minutes trying to understand how I had broken the program. Nothing made sense. I was cranky. I decided to step back and go buy some cat litter than I had forgotten, and give it a rest.

And of course when I got back, I stared at the board again. And it was immediately obvious. I had the AD9850 module on a breadboard, with all the RESET/CLOCK/LOAD/DATA lines going to the Arduino. And... that was it...

There was no common GND. I had somehow tugged out that little jumper wire. Without a common ground, it was surprising that there was any communications between the module and the Arduino.

Plugged it back in and voila. All works. Sigh. An hour of my life, wasted.

Suddenly, Erin's Modulo setup seems pretty nifty. 🙂

14May/151

Time from the ESP8266…

Yesterday, I mentioned the idea of using the cheap ESP8266 as a clock source for a WSPR beacon transmitter. My initial idea was to basically write code for the Arduino that connected to a remote NTP server, formulate UDP packages... sounds like a pain. But then I found that there was alternative software I could upload to the ESP8266 that would implement the NTP client on the ESP8266 module, and then simply fetch it with an "AT" style command.

So, I downloaded the firmware, and gave it a shot.

esptool.py write_flash 0x0000 eagle.app.v6.flash.bin 0x40000 eagle.app.v6.irom0text.bin

I rebooted, and then told it to connect to my local wifi network, and then told it to start the NTP client with the following commands...

AT+CWJAP="ssid","password"
OK

AT+CIPNTP=0

And it works! I can get this connected to the Arduino and write up a simple sketch, and it should be able to update the time really easily. This is cheaper and probably easier than using a GPS as a time source. Very cool.

Screen Shot 2015-05-14 at 9.23.10 PM

14May/151

It’s about time… (with some WSPR updates)

Yesterday I finally found a copy of the code that I wrote years ago to figure out the tone sequence for messages used by the Weak Signal Propation Reporter system. To avoid losing it again, I decided to put both the C versions and the Python versions on my github page so that even if my servers go down I'll have the code archived somewhere. If you have need of the code, feel free to use it (it would be nice if you gave an attribution in any derivative works that you distribute, but I won't go so far as to insist).

When I got home, I found myself thinking about using the AD9850 as a WSPR beacon, using an Arduino (or similar) to generate the tone sequence, telling the AD9850 to switch to those frequencies, and generate the appropriate RF. This was basically a meld of two programs: the genwspr.c code that I listed above, and a simple sketch that can be used to set the AD9850 to different frequencies. It seemed very simple, so I sat down and started tinkering.

I began by copying the genwspr.c program into a new wspr.ino sketch. It pretty much would compile as is (after I added the necessary dummy setup() and loop() entry points needed by the Arduino) but it did not generate the same code sequence as the code did when I ran it on my desktop. A moment's thought revealed the likely cause: "int" values are only 16 bits on the AVR. It actually took me a bit of time to get the types sorted out (maybe 30 minutes), mostly because I didn't remember that I should use (1UL< <n) instead of just (1<<n) to get the needed 32 bit values.

Once I got that sorted out, I extracted the needed "setFrequency" routines from an AD9850 sketch, and created a loop that would send the different frequencies at the right time. The four tones needed by WSPR are 12000/8192 (or about 1.465 Hz) apart and are 8192 / 12000 seconds in duration. My initial code simply calculated the frequency for the the given message entry, sent the appropriate tuning word to the AD9850, and then called delay(8192/12) (delay uses microseconds). Because that didn't take into account the time spent calculating and setting the tuning word, the overall message was a bit long (actually only 22ms long) so instead I did a delay(8192/12-1), and then a delayMicroseconds(22000/162). That put it right at the 110.592 seconds that are specified. (I know it's silly, the clock in the Arduino could easily be off, but I thought it would be good to be tidy. If you had source to an accurate 1PPS source, you could do a better job of this).

I was a tiny bit concerned that the tuning resolution of the AD9850 was insufficient, but consulting the datasheet, the nominal resolution is about 0.029 Hz. That should be fine. I'll dig out my SDR-IQ this weekend and try to do some workbench reception tests over the next few days.

The next bit you need to make a functioning beacon is to ensure that the transmissions start one second after even minutes. That requires some accurate time keeping. My initial idea was to hook up an old Parallax PMB-648 GPS module that I had lying around. During slots where it wasn't transmitting, it could use the time signal from the GPS to ensure that the clock had not drifted. I hadn't played with this module in a while (it's listed as obsolete on the Parallax page) so I hooked it up to the Arduino, wrote a simple sketch to read data from it, and let it run.

Frown. It's just not sensitive enough to get a lock while inside my house. I thought about alternatives for mounting it. Grumble. Didn't like that idea. External antenna? Newer module? Grumble.

Perhaps a different approach was needed. I considered the various wireless modules that I had lying around. Perhaps I could use the esp8266 modules (which are really cheap) to fetch the time with NTP, and then the Arduino could use that to trigger the transmissions.

Hooking the ESP8266 to the Arduino is not quite as straightforward as the GPS because the Arduino that I use is 5V, and the ESP8266 is a 3.3v device. I have some Sparkfun level converter boards around, but it turns out that you really only need to be careful about the TX from the Arduino. The circuit below uses a little 3.3V Zener diode to drop the voltage to avoid blowing the URXD on the ESP8266. I think I have some 3.3V zeners in my box somewhere. The circuit shows a separate 3.3V low drop out regulator because the ESP8266 can be quite power hungry, and the regulator on your traditional Uno can only supply about 50ma. I believe the Redboard has a better regulator, the MICREL MIC5205 LDO can supply 150ma, so that should be fine. If I can find the Zeners, it should be easy to breadboard.

esp8266_conn

My idea was to use the ESP8266 to send out NTP packets, parse the results... but a little googling revealed a better way. There is
alternative firmware for the ESP8266 that adds support for NTP directly via AT commands. If you send the AT command below, you'll get the time back:

AT+CIPNTP?
Time: 22:22:42 12/02/2014 GMT+02

That seems awesome. The idea will be that when the Arduino is reset, it will bring up the network and try to get the time and will figure out when the next time slot begins for transmission. When that slots begins, it can decide to either transmit, or wait until the next slot. Easy-peasy.

When I get the completed sketch up, I'll add it to my github respository.

Filed under: Amateur Radio, WSPR 1 Comment
1May/153

Playing with a buffer amplifier for a DDS…

I tinkered together a circuit for a buffer amplifier that I thought would be good to use with the AD9850 DDS board I have. In particular, for the purpose of this exercise, I was trying to preserve the nice sine-wave nature of the DDS input, and present it at the output into a 50 ohm load. I dug around and ended up creating this circuit in LTSpice.

Screenshot

(I didn't do the design, it was from my notes, but I failed to crib where it originally came from.)

I know it is is ridiculous to look at this from the standpoint of efficiency, but this feedback amp is astonishingly inefficient. Overall power draw averages at 470mw, with only 2.6mw of power actually delivered into the 50 ohm load. That seems pretty ridiculous in terms of efficiency.

Surely there must be a better way (power wise) to preserve the original waveform over a large range of possible output frequencies, yes? Or maybe not. I feel like understanding this is one of those teaching moments for me.

Filed under: Amateur Radio 3 Comments
29Apr/150

Help wanted for new project… The Big Box O’ RF

As I've mentioned over the last few months, I have piles of different development boards, and lots of little display modules and the like. I've been thinking of doing a simple radio project, aimed at helping further experimentation with QRP (low-power) radio homebrewing. Inspired by Pete and Bill over at the Soldersmoke Podcast, I thought that I might use a dev board to build a gadget which I am calling:

The Big Box O' RF

The idea is to take an Arduino (or maybe Teensy?), and connect a couple of different peripherals to it that can generate RF. I have both an AD9850 DDS module:

ads9580

And one of Adafruit's Si5351 boards, which are cool because they can generate three different outputs at once, under I2C control:

2045-00

I also have one of Jason's (NT7S) little Si5351 kits that I could assemble:

Si5351ABB-Assembled-Large.500

And of course I have a bunch of I2C display peripherals, some rotary encoders, and various power jacks. All I really need would be a nice aluminum box, and I could assemble a general purpose signal source/VFO that I could use in experiments.

Sounds pretty cool, yes?

Well, I have a few details to work out:

  • I'm envisioning a front panel which has a bunch of panel mount connectors that I can attach coax pigtails to route RF to my various project. (Probably 4, one for the AD9850, and three for outputs from the Si5351). The (semi) obvious choice would be SMA female panel connectors, and use pigtails to inject the RF into various other projects. Does anyone have any recommendations for where to get reasonably inexpensive SMA male-male pigtails? Is there a better (read cheaper) alternative that could be used? I've used Type F or even RCA jacks before, is that stupid?
  • Inside the box, would you use RG174 or RG316 to carry RF signals from the board outputs to the panel mounts? Any hints on shielding?
  • Should I make a buffer amplifier for the outputs? Or low pass filter modules (switchable?)

This project doesn't need to be perfect, but it would be nice if it was good enough to serve as test equipment that I would want to keep on my desk. Anybody have any ideas?

Addendum: This box built by Bob, WV2YAU seems close to what I have in mind:

Filed under: Amateur Radio No Comments
25Apr/150

Interested in the history of my callsign: K6HX

I was originally licensed under the callsign KF6KYI (Kenwood-Yaesu-Icom, or what I prefer, Kiss Your Iguana) but when I upgraded to Extra a few years back, I dug around and was lucky enough to snag the callsign K6HX (missed out on getting the highly desirable K6TT, which would have been AWESOME). I never really gave it much thought. I remember looking up the history of the call, and finding that it was previously held by something called the "Lew Stoner Memorial DX Club", with Donald Stoner, W6TNS listed as the club trustee. Both his call and the club call (along with a second one called the Lew Stoner Memorial DX Club East W8IMS) had expired, so I hypothesized that this gentleman had become a silent key, and nobody had stepped forward to claim his call or renew the club calls.

Tonight, I dug a little deeper, and found something interesting that I did not know.

No doubt some of you are familiar with Don. He is perhaps most famous for being the guy who first dreamed of the OSCAR: which stood for Orbiting Satellite Carrying Amateur Radio. He laid out a vision for the program in a February, 1961 article for QST magazine (if you are a member of the ARRL, you can download a copy). In it, he lays out the vision of a satellite beacon, and a later satellite repeater that could be operated and worked by radio amateurs on the 2m band. It's a very cool article, and of course now 50+ years later, amateurs achieved all he dreamed of and more. In it, he mentions that he would publish the circuit for a beacon transmitter that could be built by amateurs for "less than $15", but as near as I can tell, that article was never published.

But digging around a bit more, I found that Michael Rainey, AA1TJ, had posted an interesting article referring to a 1959 article by Don which detailed the circuit that was used by Vanguard 1. Michael has done a ton of cool stuff with old, vintage transistors, and details in his article a recreation of the original beacon circuit, which he cribbed from a 1959 article by, you guessed it, Don Stoner.

I was not able to find any references to "Lew Stoner" or to any activities by the DX Club which bears his name. Does anyone else know any more information?

Filed under: Amateur Radio No Comments
25Apr/150

Exciting AMSAT-NA opportunity…

I read this today:

AMSAT is excited to announce that we have accepted an opportunity to participate in a potential rideshare as a hosted payload on a geostationary satellite planned for launch in 2017. An amateur radio payload, operating in the Amateur Satellite Service, will fly on a spacecraft which Millennium Space Systems (MSS) of El Segundo, CA is contracted to design, launch, and operate for the US government based on their Aquila M8 Series Satellite Structure.

Complete Press Release Here

This would be very exciting. The only satellites I've worked have really worked with any regularity have been the FM satellites in low earth orbit. I'd love to have an opportunity to develop a station to work a bird in geostationary orbit. I'll be watching this closely, and probably kicking in some donations to AMSAT-NA to grease the skids.

23Apr/151

New arrivals from Adafruit, and minor updates…

I think Bill and Pete have been having way too much fun with the radio projects centered around the Arduino and the SI5351, so I decided to join them and ordered one of Adafruit's SI5351 boards (I still have the kit from Jason's Kickstarter which will almost certainly be better once I get up the nerve to do a little surface mount soldering). At the same time, I noticed that Adafruit had the new quad-core Raspberry Pi 2 boards in stock. It's likely that my hummingbird cam may be resurrected onto this board to give me a little extra CPU oomph.

IMG_0016

Oh, and the other items? I like to have plastic dinosaurs in my office, and the baseball was a ball I caught during an (otherwise completely forgettable) Oakland Athletics game.

I was informed by email that Pete was unable to achieve the same minor level of success that I had following my directions on how to get the Arduino 1.6.3 environment working with the I2C LCD display. For now, Pete seems content to use the 1.0.x versions, which I suppose is okay, but maybe we will revisit this sometime in the future. In the meantime Bill has had greater success in getting his Si5351 board working as a VFO/BFO, and has it mounted on some copper clad. Looks very nice. I should do a project like this.

Anywho... today's aquisitions will likely show up in a future post/video. Stay tuned.

21Apr/152

A (not entirely simple) LCD display for the Arduino…

I am a big fan of Bill Meara N2CQR and Pete Juliano N6QW, hosts of the really great Soldersmoke Podcast. Together, they chat about homebrewing ham radio equipment, and what they've learned in their lessons along the way. Their "tribal knowledge" is of terrific help to someone like me who keeps making small forays into the world of homebrew.

Warning: this post may be written at a level either below or above any readers experience, and either might find it boring. You've been warned. Additional warning: I probably made this more complicated than it should have been. Skip to the bottom to find the resolution.

During Soldersmoke 175, they expressed some disgruntlement with what I call "the Arduino Tower of Babel". Despite the reputation of the Arduino being the easiest way to get into using microcontrollers in your own homebrew electronics project, it can be really daunting and fraught with frustration and peril. In particular, they seemed to be having problems with trying to get various "sketches" to compile and run properly, depending on what version of the Arduino IDE they were running. Via e-mail, I offered to try to help out, perhaps being as the Arduino Sherpa that could guide them to success. While I know there are lots of people out there who are more skilled, knowledgeable and experienced than I, I have enough general computer experience to often be able to sort out this kind of problem. I thought that instead of writing this all down as an email to them both, this might serve as a good bit of knowledge of general interest to those just getting started in using the Arduino and/or programming. A lot of this won't come as much of a surprise to practitioners of the digital arts, but perhaps it might be of some use to someone (and hopefully Bill and Pete, although it appears that Bill has at least made some headway).

First of all, the way most people interact with the Arduino is through the Interactive Development Environment, commonly referred to as the IDE. It is a pretty simple looking program (well, as such things go, it can be daunting for beginners) which is actually a wrapper around several different components. What the user typically sees is a window where he can enter "sketches" (what most people would call "programs"), and a series of buttons that will allow you to load, save, compile and download code to the target Arduino board that is connected via the USB port.

Like most software that is popular, it's being constantly revised: new versions are being created all the time. Because it is what is called an "open source" project, it isn't a single company that is responsible for changes, it evolves by the contribution of many different contributors. Each "release" of the code is tagged with a version number. As of this date, the latest version of the Arduino that you can download from the primary site is 1.6.3. Because people hate to upgrade software though, many people are using older versions of the software, with some common versions being 1.0.5.

I mentioned that the Arduino IDE consisted of many different components: among these are a set of standardized "libraries" that encapsulate common functionality that lots of people find useful. When you use the Serial or Wire libraries, you are actually using code that is shipped with the Arduino IDE. These "standard" libraries usually work well right out of the box, and don't change all that often. Thus, if you had a sketch which uses those libraries, or even more basic calls like digitalRead or digitalWrite, you probably won't notice a lot of differences.

But some code is not part of the standard distribution. For instance, Pete was having difficulty getting an LCD display unit working properly with different versions of the Arduino IDE. I thought it might be a fun excuse to pick up an LCD panel to play with, so I asked him which one he used, and he emailed back this link, which seemed like a cool device. A mouse click, and two days via Amazon Prime, and I had one in my hand.

IMG_0009

IMG_0010

A pretty nice little unit, a little bigger than I expected. If you look at the back, you'll see that it's got a little board that looks a bit out of place connected to the back. It's made by the company Sainsmart, and has four simple pins connected to the back. That board is an converter which turns the display board (which are fairly common, but require a lot more connections) to instead use what is called the "I2C bus". To get this display working requires a lot less wiring: just +5v and ground, and then two data pins, called SDA and SCL (the "serial data" and "serial clock", respectively). This makes hardware hookup a lot easier than the conventional (and somewhat cheaper) models.

If you had an ordinary LCD without this backpack, you could use the standard "LiquidCrystal" library that ships with the Arduino IDE (documented here.) If you read the manual page for the "constructor" (the statement which creates a "LiquidCrystal" object that you can interact with), you can see that there are a bunch of ways to create one, depending on how you wire it up. These standard LCD panels require somewhere between six and eleven connections (plus power and ground) which can be a headache.

By contrast, this panel requires only two lines. Awesome! What's even more awesome is that you can attach other devices that use the I2C bus to the same two lines. Each peripheral has a unique "address", so programs can talk to each device independently, without adding any more wiring.

But there is a seemingly small problem, one that is familiar to users of desktop computers. To use these special devices, you need a custom library (think of a custom Windows device driver) that knows how to talk to this device. And here begins the problems that Pete and Bill had.

The libraries that ship with the official IDE are usually pretty well thought out, checked to make sure that they work well with the IDE, and are compatible. But this requires a custom library, and those libraries are not always tested against all versions of the IDE. Sometimes they work. Sometimes, not so much.

And, what's worse is that this code isn't versioned or vetted. You can have different versions of the code with the same library name. It's hard to know what versions are the best, which are later revisions and which are earlier, and which were created or modified by, shall we say, less good programmers?

Okay, back to our LCD display.

I did what I always do, I googled and found this this version of something called LiquidCrystal_I2C as the top response. That seemed promising. Version 2.0! I downloaded it and installed it (by the way, installing libraries can be annoying in the Arduino IDE, maybe I will rant about that some other day, but you can find out the "right" way to do it here), opened their "Hello World" program, compiled and downloaded and...

Nothing.

Screen glitched a little, and rows of black squares. Argh.

Double checked the wiring. Nothing seemed to be wrong. Hmmm.

Deleted that version of the library, and after some judicious surfing, uncovered this driver on the dfrobot website. They make a board which looks an awful lot like the sainsmart board. I thought I'd give it a whirl, even though it's version 1.1 (and therefore presumably older).

Results:

IMG_0011

IMG_0012

It's at times like this that I feel waves of, well, if not rage then annoyance. I haven't had the chance to figure out what the issue is (I'm an hour into this already, and it's supper time) and have no doubt that I'll be able to figure out what's going on, but it's annoying to beginners and experts alike that we have to do this kind of spelunking. Until I sort out this issue, I'll just make a few recommendations:

  • If you can use hardware supported by the standard libraries that ship with the Arduino, it's probably worth doing.
  • If you can't (or choose not to) then perhaps do some searches to find what other people are doing to get stuff working.
  • Document your success and failures as best you can on the web somewhere. Be specific as to which version and platform (Windows, Mac, Linux) you are using.
  • I actually recommend using the latest version of the IDE that's available at arduino.cc, the official website. The older versions may "work just fine", but you aren't going to be able to take advantage of the many bug fixes and updates, and if you are interacting with other newbies, your code may not work. Best to get your own house in order, and then throw stones at whoever has code which doesn't work properly with the latest official IDE.

To Bill and Pete: I feel your pain. I'd expect a device as common as this to work more or less out of the box. I'll see if I can make a better suggestion soon. You might try using the code that worked for me, but that's a poor solution really: I'm recommending using a modern IDE with old code. I'll work on coming up with a better solution.

Addendum: Pete, in your email you indicated that the I2C address for your board was 0x3F. On mine, it actually turned out to be 0x27. I found this out by using an "I2C Bus Scanner", a little sketch that runs on the Arduino and tries to find any devices by running through all 128 addresses. I was shocked to find that it's not part of the standard examples, but if you google for "arduino i2c bus scanner" you can find code for many simple examples. It should be noted that this one I found screwed me up for a few minutes by printing the address in decimal, rather than hex.

Addendum2: Sigh. I may have been working too hard. Looking at the "official" distribution, it appears that the library does support I2C displays, although as near as I can tell, it's completely undocumented, and none of the examples will work out of the box. I'll figure out the right juju to get it to work soon, and will post it below.

Addendum3: In the words of Bill and Pete:


BASTA!!!!!!

Giving up for a moment, it's acting stupidly on one of my dev machines. Hopefully what I said was not entirely wrong above, but it might be.

Addendum4: I was confused, but the rabbit hole keeps getting deeper. The version installed with 1.6.3 does not support I2C LCD displays. I was misled by looking at my installation on my Mac, which is not the standard 1.6.3, but is based on a system called platformio. When it installs code for the Arduino, it installs this version of the LCD library. You can download the code for it here. It supports both the traditional 8 and 4 bit parallel interfaces, as well as the I2C based version, and seems to be well documented. One bummer: it's thought of as a direct drop in replacement for the standard system library, so you basically have to delete the installed LiquidCrystal library, and replace it with this one. Read the instructions here. It all looks good, except for one thing:

It doesn't seem to work properly with the Sainsmart interface either.


BASTA!!!!!!

I know that part of this is that there are dozens of clones and near clones out there, and it's hard for the library writers to know about all of them, but this is genuinely crazy.

Addendum5: Wow, this is totally crazy. If you go to the Sainsmart page for the "LCD2004", you'll find a rar file which includes the library to access this hardware. Except of course, that library is years old and will only work with versions 1.0 of the Arduino IDE.


BASTA!!!!!!

That's it Bill and Pete. I'm giving up on digital electronics, and am going to spend the rest of the evening looking for good deals on dual gate FETs and crystals for filters.