Personal UV Sensor reboot

Back in 2011 one of my CFT projects was to develop a personal UV sensor for those who are a high risk for skin cancer.  Due to the limited availability of tuned UV sensors (i.e. a reliable source for UV Index rating values), I had to abandon the project. I produced one prototype, as outlined here: http://toddbot.blogspot.com/2011/08/uv-index-monitor-prototype-1.html but had to put further prototypes on hold due to  sensor procurement issues.

Well, apparently there is a rumor that the forthcoming Apple iWatch will include a UV sensor ( http://www.macrumors.com/2014/04/08/iwatch-uv-light-exposure-sensor/).  This is great if you have an iPhone, lots of money and want a new watch, but this isn't my target.

But, the new UV chip they are using, fits my budget: http://www.silabs.com/Support%20Documents/TechnicalDocs/Si1132.pdf.

I want something small (and cheap) enough that you could clip it to a hat, a UV windbreaker, shirt or blouse. Oh, and it should be water resistant (wear it on the beach or by the side of the pool) or even water proof (go swimming with it on).  It should also allow you to set a timer (in hour increments) to remind you (via beeping) to apply more suntan lotion.

The only UI would be a capacitive touch sensor. Press to see (or hear through beeps) the current UV index. Press to set timer.  LEDs (matching UV Index official colors) and/or small buzzer would be the feedback mechanism.  It should cost under $20 and the battery should last a few years (at least 5) under moderate UI usage.

Why do this?  Well, why is every (new to market) useful sensor device required to work with RF and/or interface with your phone?  Why can't tech just "be there" when you need it, rather than be "gadgets" that work with other "gadgets".

Heck, give me a 10 year battery life and I'd say you just sew the thing into clothing.

Okay, I've said way too much.  Let's just say that I am working on it.... stay tuned.

Teaching Forth Programming to kids... is really dangerous...

Teaching Forth Programming to kids is irresponsible and may hinder their progression into the professional programming industry.

So, let's do it.

One rather curious thing I've noticed about aesthetic satisfaction is that our pleasure is significantly enhanced when we accomplish something with limited tools.   - Donald Knuth, Computer Programming as an Art 

Forth doesn't have a lot of modern facilities, but that forces you to figure them out yourself.  Better yet, Forth encourages that you solve the problem at hand (rather than build elaborate frameworks).

I've been called out, in this blog somewhere, for promoting archaic old principles that don't apply to modern development.  But, I don't actually want to force people to learn this stuff. Find your tool and if it helps you do amazing things, stick with it.  

I've been programming in Forth since 1984.  I've learned a dozen languages since.  Forth is still the one that focuses my attention on problem solving better than any other.

Why am I writing this now?  I'm a bit late, but I just discovered this: Gforth for Google Chrome.

It's a toy right now (apparently no persistent file I/O), but I want it to be real.  I want to fire this up in a classroom full of kids and get them hacking.  I want them to build their own abstractions. I want them to see what middleware really is (a bunch of layered restrictions with the goal of making things more structured and easy, while in reality making you conform to things they want to keep hidden -- okay a rant for another day).

Sure, underneath Gforth for Google Chrome there are layers upon layers.  But there is a lesson there too: Its all about simulation.  It's Turing machines all the way down.

Statically Typed Languages like C++ and Haskell are good for lazy programmers (like me)

I've seen my errors in production code. I'm doing a forensic analysis of some "embedded" software I shipped to a customer.  By embedded I mean there is no UI and it is supposed to run unsupervised 24x7.

Server (Cloud) software often meet this criteria, but sometimes we cheat and log in (to see how things are going) or restart the OS when things aren't quite right.

But, that's not quite embedded. By embedded I mean "It has to run without me or the user intervening." and "There is no such thing as rebooting to fix a problem."

Now, I love developing code in Lua, so this isn't a Lua criticism, but when I review my daemon logs and see that the process died because I was trying to add a number to a "nil" value, I cringe.

On this same system I have a Haskell process also running.  The only time I saw it had died was when I didn't handlebeing fed bad data from a corrupt database.  Not exactly the same class of bug...

The Lua code problem could have been caught with unit tests or code review (maybe), but I am sort of a lazy programmer.  I can fall back on lazy habits such as "this is so obvious it can't be wrong".

Haskell doesn't let me do this.  It won't let me go on tossing untyped variables here and there . It won't let me assume that I never pass a string as a number (or vice versa).  It forces me to be precise.

Compiling modern C++ (C++11) with warnings on (in clang++ or g++) is similar.

I hate to say this, but after continually abandoning C++ (in cycles: 1992, 1997, 2002, etc), I am back again and I like what I see in C++11.

I'm writing deliverable code at work using C++11 and I just tried my hand at using it, *instead* of a scripting language, to do some configuration file handling.  C++11 for scripting?  Yes. And it seems to work.  Not a pointer in sight. (Actually that would be the only sane way to do this in C++: rely on RAII.)

All that being said, and especially to any potential employer who may be reading this: I am not really a lazy programmer.

The IDE called Forth, or.. Forth I wish I knew how to quit you.

I've been playing with OpenFirmware. Yep, booting it off of a thumb drive (via Grub2). It takes less than a second to boot on a "fast" laptop up to the Forth "ok" prompt.  At that point, I can start playing around with low level hardware.  Open Firmware went so far as to provide a "GNU readline" like capability where I can use Emacs-like command line editing and completion of words.

But, wait, there is no command manual!  What does this word do?  Enter "see" and the word you are interested in and view disassembled source code.

People (still) underestimate the innovations built into a "classic" Forth.   Gforth still has some classic capability built in.

Here is what I had with Forth during the 1980s (on Commodore 64 and then Atari ST):

1. Full screen block editor.
2. "See" or equivalent for looking at source.
3. The ability to ask the block editor to locate the "real" source and let me edit it (i.e. Tags).
4. The ability to play around with graphics and other hardware facilities.
5. Very fast start up (or restart for when I crash the machine).

This was the basic Forth IDE.

I'm a long time Emacs user (25+ years)  and I still not at that same IDE productivity level I was with Forth back in the day.

Smalltalk (in particular Squeak) has been the only other things that has come as close (for me).

I know that machines are bigger and software is a lot more complex these days, but why can't I have that same feeling of "being one" with the machine?

Here is what I want:  I want to load up an interesting library (e.g. libpcap, OpenCV, etc) into a Forth (e.g. Gforth) and explore.  I want to play.  Lua, Perl and Python can get me half way there (i.e. bindings), but I still have to grapple with a REPL that doesn't seamlessly integrate with the editor.  

Yes, yes I know you can bend Vim or Emacs to do these things, but the resulting IDE isn't as natural (IMHO). You are still piecing together a generic editor, a command line (linux shell) and a programming language. (For example, how do you list a directory in the chosen language? Oh, you use the shell or editor? Are the results first class elements for the language?). 

Some would say that Visual Studio is a great example of a seamless IDE, but it is still working with a language that isn't naturally "interactive".

This is why I still hang onto Forth. It isn't about Forth building better apps. I don't care what an app is built in.   It isn't about the destination, its all about the journey.

Todd's 1 question test for all new "advanced" dynamic scripting/programming languages.

Whenever a new language comes out I have a simple test to see if it is worth looking at.  I came up with this test back in the 1990s after being frustrated by the state of "advanced programming languages".

In the 1980s, as a lowly FORTH programmer, twiddling 8-bit bytes, I was blown away with my first experience with Lisp. It was on a DEC2060 (running TOPS-20) and was called "Standard Lisp".

As a student, back in 1984, I coded up a small lisp function to compute the factorial of 120.

The terminal presented me with:

6689502913449127057588118054090372586752746333138029810295671352301633557244962989366874165271984981308157637893214090552534408589408121859898481114389650005964960521256960000000000000000000000000000

My mind was sufficiently blown.

Of course, the largest factorial computed by a programming language where the number/integer type is matched to the machine word size is much smaller.  I had already programmed in Pascal, FORTH, a bit of C and BASIC.  But, this was the first language implementation I had seen that wasn't bound by that machine word limitation.

(I quickly followed that exercise by coding for the factorial of increasing numbers until, by the time I was in the hundreds of thousands, the terminal responded with a message saying that it was taking too many resources and that the process was being "spooled" -- whatever that meant.  I went home and the next morning I was greeted with an email from the sysadmin requesting that I come get a "print job" from the ops center.  I rang the ops center door buzzer, the admin came to the door and asked what I wanted. I told him him who I was and he then frowned, told me to wait and closed the door. A few minutes later he showed up with a hand truck loaded with a big box of green bar printer paper.  Apparently, "spooled" meant the result was being submitted as a print job).

A couple of years later and I discovered that Smalltalk too had this "big num" (or arbitrary precision) feature.  Why wouldn't every language have that? (Yeah, I know... performance...but, still...)

Now, when I am presented with a programming language that is supposed to be the "next step",  I look to see if it supports bignum.  Now, when I say support, I don't mean surrounding the number by quotes and submitting it to a bignum library. That's cheating. I want to say something like:

X=6689502913449127057588118054090372586752746333138029810295671352301633557244962989366874165271984981308157637893214090552534408589408121859898481114389650005964960521256960000000000000000000000000000  / 19;

I don't want to type it as a string. That's saying that there is something "special" or "hard" about large numbers.  Why, in 2014, should I be concerned about whether a number fits into 32 or 64 bits (or in the case of Lua and Javascript: a 52 bit mantissa)?  I want tnative/natural support.

So, what other programming languages pass this bignum test?

• Erlang does. 
• Haskell does... sort of... got to choose the right type.
• Perl does (and has for a while.. just type "use bigum;"  and all following numbers are not bound by machine word size.

Now, don't get me going about native/natural support for rational types.

/todd

Perl is 26 years old?

I just read on Hacker's News that Perl turns 26 years old today.  My oldest piece of open source software is written in Perl. AFT.  AFT was coded in Perl 5 back in 1996 (which makes it over 17 years old).

I originally wrote AFT in awk (sometime during the early/mid 1990s) . I ported it to Perl by using the awk to perl translator (a2p) as a starting point.

Every once in a while I revisit AFT to see if there are any new tricks to add or just to clean up the code and make it a bit more Modern Perl.  AFT is still in the Ubuntu software repository, so you can install it under Ubuntu by simply doing   sudo apt-get install aft.

I'm still using Perl. I am doing some funky stuff with the AWS cloud (EC2 instances) and find Lincoln D. Stein's VM::EC2 package fits my needs.  Perl is still great for replacing nasty bash/sh scripts (although some would say I am replacing the nastiness of  bash with nastiness of Perl).

I'm not much of a CPAN user, but those who know me understand that I am very selective of libraries and frameworks. I prefer to avoid layering and loading lots of dependencies. What I find attractive about Perl is how much the basic distribution can get accomplished  (e.g. I don't have to resort to libraries so quickly as when I program in Lua).

I'm particularly interested in investigating Mojolicious for use in my elderly monitoring project.  I use LuaJIT primarily on the base station (with a bit of Erlang).  The cloud side is currently a fair amount of Perl.  But aren't there better languages to do cloud/web development?  Isn't Perl old hat?

For those folk who think that Perl is old hat and doesn't have a place in the modern Web, do you use DuckDuckGo?  It was developed primarily in Perl....

Power Considerations for an HVAC Thermostat (10 years off a couple of AA batteries?)

Hear a tick coming from your thermostat every time it turns on the heat or AC? Well, assuming you have an electronic/digital thermostat, you are hearing a latching relay.

Latching relays are wonderful power miserly switches. Unlike a solid state relay, which requires control current (anywhere typically between .25mA and 20mA depending on what you choose), a latching (mechanical) relay will latch (hence it's name) when pulsed.  A short burst of 100mA or so and you are done.  If your thermostat is switching the HVAC once an hour per day (which is pretty excessive), then you are still using a lot less power than a solid state relay.  Another potential problem with solid state relays is heat. They generate heat. They can overheat and if you don't choose and place your components wisely, they can affect the temperature sensor.

With latching relays,  your modern latching thermostat is not consuming that much energy.

Interestingly, I believe that the NEST uses solid state relays.

A quick google shows that some NEST customers are having battery issues. Here is an interesting one:

http://support.nest.com/article/A-low-battery-level-will-cause-Nest-to-disconnect-from-the-Internet .

This is the kind of issue I want to avoid.  The two household gadgets that I don't want to think about (battery) power problems are my smoke detectors and my thermostat. I'll check once a year, but beyond that...

Here is a target: Ignore UI and wireless for a moment. Once a temperature schedule has been set, can you design a thermostat that will run for 10 years off of a couple of Lithium AA batteries?  That is my starting point.

So, as boring as "Thermostat design" sounds, it poses an interesting power problem.  Add sophisticated 'internet-of-things' functionality and now you have two problems.

An Alternative Take on Thermostats

For most thermostats (including NEST), there seems to be a power/location problem.   At best you have 24VAC control lines you can parasitically suck for power or (worse case) you have some AA batteries that you hope will last a couple of years.  With batteries you start to seriously limit what your thermostat can do (a reminder htat your thermostat is NOT a general purpose computer).  With parasitic sucking off the control lines you start playing games with how to ensure that you always have enough power (OMG,  HVAC off for maintenance or power outage and what should the thermostat do?).

So okay, we've got a power management problem.

A question:

Why is your thermostat's primary User Interface (UI) mounted to a wall (and often in a place not where you are comfortably located)?

The location of your thermostat probably has a lot to do with the "best" place to measure room temperature (out of the sun) and where you can run HVAC wires.  There are other factors, but it doesn't matter.  I have to get up and go there to read or adjust the temperature. (Of course, with NEST and other networked thermostats you can change temperature from almost anywhere).

A proposal:

Don't put the UI into the thermostat.

What?  But where do we put it?  Surely not rely on the smartphone, right?  Yes. But consider this:

The thermostat will now consist of a small discrete box (hide it behind a picture frame or paint it to blend in) with a temperature sensor (maybe), the required solid state relays to control the HVAC, a couple of AA (or AAA) batteries, and an small RF transceiver (433MHz if you desire).

Pick a convenient location (or two) and install the UI there (and a temperature sensor too). It can be on the wall, on the kitchen counter, maybe a shelf, etc.  The only requirement is that you have AC power (see where I am headed?).

Now, let's rename this UI a "control center". This control center (still very small) can not only host the UI but can also support Bluetooth and/or Wi-Fi, so you can use your phone to control the HVAC from your bed or couch.

If we do the RF correctly it can be safe (validated/encrypted) and reliable.  Because the control center is plugged into AC, we don't have power management issues. The thermostat itself is running off of batteries or even parasitic power.  We still have some power mgmt issues, but we can duty cycle the RF to reduce the overall power consumption. (A thermostat's control loop is *never* under immediate control of your thermostat's UI -- you "advise" the control loop what to do, so a couple of second lag is okay).

Now, with this setup we can put a lot of sophistication into the control center. It can be a (shudder) computer and suddenly our thermostat can become something much more interesting...

Thoughts of a Haskell (or Erlang or Lua) powered thermostat starts to become more of a possibility.

/todd

A Better Thermostat (or is the Nest the best we can do)?

I've been reading about the Nest and I am convincing myself that it is too gadget-y.
I'm thinking about my household and the usual elder market that I am currently designing stuff for.

Do I really need my thermostat to be Internet enabled? Do I really need to become a honeypot for Black Hats?  Do I really want my thermostat to have software "updates"?  Also, it is yet another device to be managed whenever I swap out routers or change wi-fi passwords.

However, I do think that we can do a lot better than the HVAC's perception of what a digital thermostat is.   Honeywell Prestige 2.0 and Ecobee Smart are the current competitors for the Nest. But they seem to think that we all want bling in our thermostat interfaces. Lots of color, lots of funky icons -- yes! Just a slide of a finger.  Here is where I think the Nest got something right. Grandma can just turn a dial to get the desired temperature. No capacitive touch screen (what about those with crippling arthritis?) and no busy trompe l'oeil effects for those with bad eyes.

Nest, apparently, runs Linux on a Cortex A8. That is a power hungry beast. No wonder it has a rechargeable Li-po battery inside.   It uses the 24VAC to charge it. (If you don't have a Common wire, and I don't, it does this clever but dangerous trick of pulse the fan/AC/heat trigger line to complete the circuit and trickle charge the battery -- apparently that cause the start/stop ping of death on HVAC units that don't debounce away the false triggers).

Then there is the problem of what if you use the interface too much, run buggy software updates or spend too much time on wi-fi. You'll drain the battery, right?  (The trickle charge takes time and you are always running off the Li-po).

I don't think Linux is ready yet for 24x7 systems that run off of battery.  (A tickless kernel is a must for battery longevity, and that is just a start). But I could be wrong.

There are advantages to running an OS. It opens up development options: I'd love to try and get some Haskell code into an "embedded device".  Without thinking about embedded development issues, you can focus on the algorithms.

What about the power miserly Cortex M4s?  They are starting to come with a lot of RAM and massive flash spaces.  I've even seen Haskell (and Lua) running on STM32F4 Discovery boards. But we are still only talking about kilobytes of RAM. Until I see real applications run, just blinking LEDs and toggling a few GPIO pins doesn't convince me that you can write serious sized applications for it (where memory allocation can kill you).

For a smart thermostat, it is all about the algorithms. There are, at most, 3-5 interfaces to the HVAC systems. These are basically switches (relays or solid state relays).  It is all about when to turn these switches.

I've been toying with the idea building upon Forth to do smart thermostat stuff.  If I stick to an ANS flavored Forth, I can implement it on bare metal and eventually up port it to an OS when they become appropriate for battery based systems.

What about Wi-Fi and stuff?  I have more to say about that later (e.g. I'd be happy to just use my smart phone in local proximity with Bluetooth to control and data-mine the thermostat).

Haskell and the Embedded Programmer

Can you really use Haskell for Embedded Programming? Well, if you define your embedded platform as (at least) an Intel Atom based computer with gobs of memory... then probably. (Yes, I know about GHC ARM, but has anyone deployed real world apps with it?)

Ignoring the really cutting edge (academic) features of the language, Haskell seems ideal for the embedded developer. What? Wait. Hear me out.

First, let's define the class of embedded I am talking about.  How about my home monitoring application (http://eldermonitor.blogspot.com/). The base station is headless and should run 24x7, so I classify it as "embedded".

It currently runs mostly Lua (it used to run Erlang) on Linux, but it could have been Java on Android OS for that matter. If you accept the notion of a garbage collecting dependent app can run on an embedded platform, then you've made the leap (for good or bad) to modern embedded development.

Unfortunately, all of these modern embedded systems don't seem to run all that well.  My Android phone pauses every once in a while (garbage collecting I suspect) and my Roku crashes after a few weeks of up time.  I am starting to worry about the stability of my home monitoring system (although it has run for a couple of months before I intentionally reboot it for upgrades, etc).   Not just due to garbage collection, mind you.

Now, Haskell also does garbage collection, but the compiler is backed with a lot of type checking and other supports for determinism. The idea is that if you code "safely" (say it with me: catch all of those potential exceptions -- they will bite you later if you ignore them), you have a better chance of avoiding run time errors.  Avoiding run time errors are very important for systems that run 24x7 with no head (display).

Erlang's "expect to crash" approach is a good meta level approach to embedded design, but if you don't have a careful design or code, recoveries from random crashes is not a good thing. Your embedded code needs to be correct. Every crash situation is bad. It is worse if the problem is due to bad code logic (and not a perfect storm of resource conflicts).

Haskell is no panacea, but I've done 3 projects in Haskell thus far (one embedded in a commercial system) and I haven't been bitten by any type-based run time problems.

So, Haskell (or a sane subset of) appeals to me for embedded development.  But when is it overkill? I haven't done a lot of sophisticated stuff with it (yet), so almost everything I've done could have just as easily been done with Erlang or Lua.

Haskell was a bear on some of these projects, but I'm finding the results encouraging.  I feel better about the resulting systems.  Maybe it is time to revisit using it for my Home Monitoring system.

The 8051 won't die... will it?

The 8051 8-bit MCU architecture was introduced, by Intel, in 1980. It is still in wide production by at least a half dozen vendors (including my fave -- Silabs) at prices as low as a half a buck.  My current favorite is the C8051F988 (currently used as the brains behind my sensor nodes). This MCU costs about $1.60 (for low volume purchases) and is essentially an 8-bit SoC.

The C8051F988 comes in a couple of packages, one of which is hand solderable. It requires no additional passive components (an internal oscillator can run at 25Mhz), but I usually throw a capacitor on the power supply pin and a 4K resistor pulls up the RST line.  It has a mere 512 bytes of RAM and 4K of flash (a beefier version can be had for around 1 dollar more). I program it in Charley Shattuck's MyForth, so the memory doesn't feel so constrained.

The C8051F988 has an ADC, internal temperature sensor, a UART, SPI, I2C, etc.  It executes 70% of its instructions in 1 or 2 clock cycles.

Here is the power specs (from the datasheet):

Ultra Low Power Consumption
- 150 µA/MHz in active mode (24.5 MHz clock)
- 2 µs wakeup time
- 10 nA sleep mode with memory retention
- 50 nA sleep mode with brownout detector
- 300 nA sleep mode with LFO
- 600 nA sleep mode with external crystal

I'm impressed. But, of course, why bother with this when an ARM Cortex blows it away? (Ultra low power consumption 32 bitters are starting to arrive.)

A couple of things keep me interested in this chip (and other 8051 variants), and that gets us to what this blog post is about.

First, look at the part count: For under $2 (hobbyist pricing): the 8051 chip, an (ebay provided) SOP board, a resistor and a capacitor.  I have the old Silabs serial ec2 programmer (for initial flashing of a forth bootloader) and use Silabs free programmer under Linux WINE.  No ARM I know of has this simplicity.

Second, and most interestingly, the 8051 architecture doesn't seem to want to die.  Its a relatively simple chip (low gate count) and can be easily implemented as an FPGA core.  When you want to do simple things, it is very handy. It is built into *everything*: Keyboards, microwaves, the new Bluetooth LE chips (like the popular TI CC254x chips).

Start taking stuff apart and you are likely to run into an 8051.

They don't want to die. Somewhere there are engineers who sniff at the new 32-bit Cortex M series (meant to replace those old 8-bit 8051/AVR/etc processors) and then get their job done with assembly or C code that has run solid for the past 30+ years.

Scale if you must, but don't forget reliability

My home sensor base station is using STOMP to transfer sensor node messages into an AWS cloud instance (running RabbitMQ).  I am using STOMP because I can't find an AMQP binding that supports SSL (outside of Java and Erlang).  Or, more to the point: the sensor base station runs Lua and my AMQP binding for Lua is with  amqplib (which doesn't support SSL).  My pure Lua STOMP binding runs over SSL. But I digress...

The STOMP client runs 24x7, pumping messages into the cloud hosted RabbitMQ at a rate of 2-3 messages per minute.  This is not a lot of traffic, but I expect it to scale.

In order to develop (and test) the "server/logic" side of the system, I am running the consumer of messages on my laptop (it connects to the AWS RabbitMQ as a consumer).  The consumer is also talking STOMP.

However, when my laptop lid is closed, all consumption stops. So, for example, overnight I can accumulate a few thousand sensor messages.  Firing up the consumer in the morning should just suck all those messages down and pick up where it left off. Unfortunately, there is a glitch (in RabbitMQ?) where after a few hundred messages (all ACK based -- fault tolerance, baby!) it stops receiving new messages and the remaining messages are marked by RabbitMQ as "unacked".  Restarting the consumer happily consumes a few hundred messages before the same glitch re-occurs.

This is a serious problem and I need to figure out if RabbitMQ is the culprit.  Interestingly, I found that by slowing down my consumption rate (read/respond every 100ms) the problem is fixed. Argh.  Well, that won't scale, now will it?

So, until I figure out what the real problem is, I'll keep consuming as fast as I can.  But, what about the unacked messages? Well, this is where "reliability" comes in.  By default, all of my consumers do timed reads. If they don't receive a message in 60 seconds, then they terminate. (I don't use RabbitMQ heartbeats. I have an "application" level heartbeat that makes sure the whole system flow is working from base station to cloud. This heartbeat fires every 30 seconds).   Failure is an Erlang technique. The consumers are written in Lua, but I did learn one thing from Erlang: Failure is okay, just plan your recovery.

So, once the process terminates, Ubuntu Upstart restarts it.  The result: The system recovers on its own from this bug.  The system continues to run.  The unacked messages are requeued and delivered.

Scaling is great, but don't forget reliability!

Using Forth to question the Status Quo

Whenever I face a  tough problem I try and break it down to the essentials.

Often using traditional methods only leads you to traditional solutions.  Sometimes traditional solutions are just fine, but what if you need something special?

This isn't about programming in Forth. It's about taking the Forth Approach. This means looking at the problem in a different way.  You can use your own favorite language, but consider the path taken (time and time again) by Chuck Moore (Forth's inventor). His chip designs are novel. His approach to problem solving is stunningly minimalist.  Go ahead and google him, I'll wait...

Sometimes is worth it to think; "What is the simplest possible way to do this?".
In my mind, simple doesn't (necessarily)  mean easy.

Consider designing a wireless temperature sensor.  You want to mount them in every room in your house. Now before you whip out your Raspberry Pi, consider three factors: Cost, Power and Size.  This sensor should cost under $20 in parts, be discrete enough to attach to a wall, and should run for at least 1 year reporting temperature once per minute.

Now, thoughts of Wi-Fi enabled Raspberry Pi (too power hungry and expensive) wane. How about something with Bluetooth LE? ($15 at best; no money left for the board, battery and other parts, plus you have to deal a fairly complex "standard").

I've discussed my approach a year ago here (Why Forth still matters in this ARM/Linux...). It basically describes a $7 RF transceiver and a $3 MCU (that requires only a couple of resistors and caps to function).  The MCU has a built in temperature peripheral.   I hand wrote an implementation of RC4 for a modicum of security. I've coded this all in Forth, but I could have used C. The implementation language doesn't matter -- the approach is inherently Forth-ish.

A year later and I still can't find anything cheaper.  The status quo says I should go to Bluetooth LE (or at least Zigbee). But, at what benefit?

Update:
Okay, this is an even cheaper RF transceiver (just $2.99, but in the crowded 2.4GHz band): http://www.ebay.com/itm/HopeRF-RFM73-2-4GHz-Transceiver-/251209604525?pt=LH_DefaultDomain_0&hash=item3a7d425dad

Complexity and the Future: Revisiting technological foundations of Smart Phones

Every once in a while it is good to sit back, take a deep breath and look at the state of things.

As technology hurls forward we accept building complexity upon complexity.

The Internet is very complex. Fine. I would call it "deeply" complex. In that manner, it is similar to an organism. However, it is based upon a very simple infrastructure called IP (Internet Protocol). Upon that we have a host of other protocols with the most pervasive being TCP.   From there, the complexity escalates rapidly.  But that's okay.  Underneath is TCP/IP and I can always grab hold of it -- it is the earth, solid and firm beneath my feet.

Now, my phone is very complex. A Smart Phone is  made up of a bunch of software. Let's consider Android. Underneath is a Linux kernel (but you can't normally touch that -- imagine floating about the earth just a few inches but never touching ground). On top of that there are processes, a VM, and a bunch of apps.  Oh, and off to the side is the actual phone stuff (sacred and untouchable).

Every once in a while the phone gets slow or needs a reset.  It is indeed a complex beast.

I'm okay with the Internet being unfathomable by a single mind, but my Smart Phone is headed firmly in that direction. So many things working together, so complex. But, unlike the Internet, my phone's software is not self healing. There is no notion of routing around bad processes or chips. When bad things happen, the phone is nearly useless.

What if I want to just make a phone call? Or perhaps send a text message.  Maybe all I want is to message someone over the internet or read my email?

What if we stripped a smart phone of everything but the communication essentials.

Nokia is trying to (re)find a niche. They are offering a new phone for the third world: http://www.nokia.com/mea-en/products/phone/105
This will sell for about $20 in the European market.  The standby time is 35 days.

If there were a bunch of these phones deployed with free text messaging, what could you do with it?
What if there was a slightly better alternative to SMS (larger payload). Or perhaps a multi-segment protocol on top of SMS that the phone could parse.

Why does the entry level into the 21st century Internet require a Smart Phone ($$$)?  Why can't I have a slightly dumber phone that plays well on the Internet?

Home Alone Elderly Monitoring System now has its own Blog

Starting today, I'm posting all of my notes on my Elderly Monitoring system here: http://eldermonitor.blogspot.com/

All of the old home automation  material will remain here, but look for new stuff on the new blog.

A Pattern Language for Haskell System Programming?

Continuing on my previous blog entry (Haskell for the Working Programmer), it occurs to me that there needs to be a set of idioms to define a Haskell for System Programming.  Or, perhaps more strongly: There needs to be a Pattern Language for developing System Programs using Haskell.

When I say System Programs, I am stretching the term a bit to mean an application that touches the real world a lot. That is, it isn't so much focused on doing a ton of data manipulation or business logic, but spends most of its time interacting with the system (hardware, OS, or network) at hand.  This is the land of embedded development, network tools and server management.  Haskell can play here, but I don't see a lot of literature about how to do this.

Haskell is a rich ecosystem for implementing cutting edge ideas. This is its academic heritage and it keeps the language healthy and forward looking. But for us working programmers, we can't always be interrupted from our tasks to explore new mind blowing techniques (e.g. "Okay, I grok Monads, so let's get some work done... whoa, wait... Arrows? I need to start using Arrows?").

So, you want to build Home Monitoring base station (something to collect sensor data, analyze it and perform some action or notification via the Internet).  Oh, and it needs a built in web server for configuration.

How do you do this using Haskell?

That isn't quite a fair question. A Haskell newbie would not be advised to adopt such a big project until they've mastered the language a bit. So, let's ask again, but a little more focused:

I'm an Erlang/Clojure/ML/Scheme programmer (so I understand FP); I've played around with Haskell and now I want to implement my Home Monitoring base system. Where do I start?

That's better.

So, what is needed here is way to guide a developer towards their goal with just a subset of Haskell. (I've recently written over  3000 lines of Haskell for a commercial system. It doesn't sound like a lot, but since it was mostly system programming stuff, I leveraged lots of Hackage libraries and FFIs.  In retrospect, I would say that I used a fairly small  subset of advanced Haskell features to get the job done.)

An aside:  I mentioned  the phrase Pattern Language as opposed to Design Patterns.  I don't want to bring up an old war in the Pattern Community (is there an active Pattern Community these days?), but I am talking about a group of related Patterns (or Idioms) that you can select to help you build a specific thing. Patterns in a Pattern Language are not adhoc. Each Pattern leads to one or more Patterns you may choose to help you build the thing. Check out the original source for further understanding and information. (I'm too lazy to find a great example of a software Pattern Language for system programming, but you can look at my own 1997 contribution to the community: A Pattern language for User Interface Design for the general idea of what I am talking about.)

Now, where were we? Subset of Haskell...

This subset of Haskell wouldn't be restrictive. By all means, if an advanced Haskell technique helps get the job done or makes the program more manageable, then use it.  But Haskell has an ocean of ideas and new users are apt to drown in lieu of getting their project completed.

You don't need to master all of Haskell, just master what you need.  Just by using Haskell (in particular the type system), you are already on your way to constructing correct system programs.  (But, please remember to handle exceptions -- the monadic wrapped real world is full of unexpected behavior).

So, what next?  I don't know. I am wondering if something like The School of Haskell would be a good place to start building such a pattern language (where examples could be not only listed but tried out).

Haskell for the Working Programmer

There is a need for a book.  I would call it "Haskell for the Working Programmer".
The audience would be, you guessed it, working programmers.  Maybe even for working functional programmers.   I already grok functional programming. I have been doing it for over a decade now. It is Haskell I'm trying to grok.

Sure, there is Real World Haskell, and it is great. But, it is also getting dated and perhaps the pacing is a bit too iterative for my tastes. That is, they start off with sub-optimal (naive) solutions to problems and then (in later chapters) proceed to make them better and better.  Too much reading!

As a working programmer, I tend to learn better by studying and stealing exemplars. 

Maybe I want a cookbook.  Or, perhaps, what I am really looking for is a book that recognizes that my first goal is to compose a working program.  Of course, I want to understand why something works, but maybe, just maybe, I want to see something (anything) work first!

Should I feel ashamed that I still haven't mastered Monads?  (Sure, I've used them, debug them and have even constructed a few, but I can't say yet that I have mastered them -- at least not the theory). Can I call myself a Haskell programmer?

Read this: http://www.free-variable.org/2012/08/i-remember-the-time-before-monads/  by Paul Callaghan (you can skip down to the Monads section).  It rings true.

In this way, I feel that Haskell is a bit like Perl.  You can write lots of good, usable Perl without diving into the deep dark arts of Perl objects (bless them).  And, you don't have to write a CPAN module to be a productive Perl programmer. The Perl community has accepted this (or at least seemed to).  Do a google for Haskell and you'll find lots of  computer science-y (aka research) blogs and perhaps a dozen or so explanations on why Monads are easy, how everyone uses them and then you feel dumb when you can't figure them out.

Haskell needs more Working Programmers. Erlang seems to have snagged them all and it was the Monad that scared them away.

P.S.
If you live in the DC area and want to meet with (at least one) Working Programmer, consider joining the DC Area Haskell Users Group and help make it a reality.

Intel Atom (Haskell) vs ARM (Lua) for Home Monitoring Station

ARMs are cheap and plentiful, but computationally limited.  I'm looking to do some image processing (motion detection is done by cheap webcams rather than PIR sensors) using OpenCV. This should work on an ARM, but how slow will it go?

Haskell doesn't have much of an ARM presence and I can't rely on bindings to port well.  If I use Haskell (and I have already prototyped some motion detection using Haskell and OpenCV), then I'll need a beefy server. Why?  Imagine 5 or 6 motion detectors working in parallel to form a comprehensive picture of movement in a household.  Plus, some of the visual detection is fairly fine grain (detecting steam, smoke and burner flame from a stove -- more on that later!).

I feel like I am selling my ideas short by going with ARM (at this point). I'd toss the Haskell code and use Lua (upon which I've also done some OpenCV prototyping).

What is the state of small (set-top) Atom PCs?
Well, this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16883220294  looks promising ($244). The price is a bit high (compared to Android/ARM stuff out there), but it can be a good system to target.

/todd

Home Monitoring / Elderly Care project reboot

This blog has been an  on-and-off  forum for my Home Monitoring project for Elderly people. (A non-intrusive, internet aware means of keeping track of Grandma/Grandpa).

For the past year I've been exploring different technologies, from X10 to Z-Wave to Cameras to homebrew sensors.

Within just a year, prices have dropped dramatically on embedded (ARM) computers, Android tablets, and USB/Wi-Fi cameras.  I'm not so much dedicated to cheap hardware, but I am open to any options given the steep prices for Z-Wave and other proprietary tech.

More info to come.  This is going to be interesting and... different.

For background, check out:

http://toddbot.blogspot.com/2012/08/webcam-based-motion-detection-unix-style.html
http://toddbot.blogspot.com/2012/06/my-home-monitoring-project-goals.html


Stay tuned.
/todd

Thinking Big and Home Monitoring?

Sometimes I think too small.  I come up with a small idea and pour a lot of time into it,  cutting and polishing diamond from stone.  That is fine. That is where I spend a lot of time. But that is not me.

I like Big, bold ideas.

Now is a good time to be looking for Big Ideas.  The internet is huge.  It is the largest thing that humankind has devised. But it is not a single thing. It is not a networked collection of servers and clients. It is the essence of virtual. We run our ideas in virtual machines.  We use virtual memory.  In our distributed, concurrent web of things we don't ask how big, but how many?

What if my home monitoring project isn't really about a bunch of internet enabled sensors. What if the sensors are just players in a virtual network that represent home.  How do I make sense of all of the collected data?  How do I maintain privacy?  How do I make of all of this ubiquitous?

The Nest smart thermostat is a diamond.  It has one task and it does it (apparently) beautifully.
But I am interested in the bigger picture.  I'm interested in a more radical idea:

What if  you could monitor your home by modelling your home (sensors)  as intelligent agents in the cloud?  What if this model ran on a virtual network dedicated exclusively to you?  What if you virtual network of sensors could tell a story (a story about the well being of your home)?

What I don't want:  An alarm sent to my phone notifying me that Grandma's stove has been left on for over an hour without any sort of movement in the kitchen.

What I do want: An alarm sent to my phone because it is 11pm, the stove is on, no one has moved around in the kitchen for 20 minutes,  the TV is on in the bedroom and Grandma has never used the stove that late (her profile has shown that she has never used the stove after 9pm).

I dunno. There is a realistic, big idea somewhere in there. I just need to tease it out.

Next week I am heading off to the San Francisco Erlang 2013 conference.   Hopefully it will remind me that I am not a diamond cutter.