Brian Krontz has done it again. The instructions for ClockTHREEjr have been posted. We will update the manual periodically. In the mean time, please check here for updated and clarification.
ClockTHREEjr Instructions and Errata
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Author Archives: wyojustin
Raspberry Pi, à la mode?
Lot’s of people are excited about the Raspberry Pi, a complete computer for $25 (or $35 with ethernet).
The initial shipment is entirely sold out, and there are 200,000 more on order. Lots of people have been saying that this is the end of the Arduino, as it’s about the same cost, but is a full linux system with keyboard, mouse, and hdmi video output.
We think this is an oversimplification. Arduino is fantastic at interfacing to the physical world in a way that no linux (or Windows) PC could hope to approach at any cost.
The Pi does have a GPIO connector, but it pales in comparison to the humble Arduino. No built in PWM (servos anyone?) and no Analog to digital conversion.
We consider both platforms complementary to one and other, like pie and ice cream. Of course we call the result “Raspberry Pi à la mode”, the Linux side handels all of the displays, human interfaces, and number crunching. The low power Arduino compatible “à la mode” board handles sensors, motors, and provides a highly accurate real time clock. 
“À la mode” is an Arduino clone specifically designed to interface with the Raspberry Pi. You can of course connect a standard Arduino to a Pi USB port using a cord, but when you want a turnkey solution, how about an Arduino compatible “plate” (what the Pi folks call shields) that fits right on top of the Raspberry Pi with direct access to GPIO port?
You can plug your existing Arduino shields right in, and you can even run the Arduino IDE on the Pi. Since the Pi’s core mission is to provide equal access to computing to all children, this will also give the kids the opportunity to mix it up “Arduino-style” with real world hardware.
We couldn’t have a vanilla add-on, so we added:
- A battery backed real time clock: RTC: DS3231 (same as ChronoDot)
- uSD card for logging
- Socketed Atmel Atmega 328p in case you make a wiring mistake and need to replace it.
We’re sending off for prototype boards soon, so if you have feedback, let us know!
Inside SeeedStudio, ClockTHREEjr Assembly
Nana Chou took these great production photos of the ClockTHREEjr final QC checkout. I guess we figured these would be assembled deep inside the bowels of some enormous building. We were pleasantly surprised by the lovely work environment at Seeed Studio.
Not only do they care about Open Source Electronics, they obviously care about the health, safety and well-being of their workers.
Way to go Seeed Studio!
Draft CHRONOGRAM2 layout available for comment.
Please comment on the CHRONOGRAM2 draft layout. Here are the zipped images if you want to look through them one at a time.
Post comments here or on the forum: https://wyolum.com/forum/showthread.php?tid=56.
Thanks!
Justin
GPS Disciplined RTC
The power packed I2GPS board (photo by Brian Krontz)
Here is a sneak preview into a product we are working on: the I2GPS. The I2GPS is a slightly modified I2SD. The only difference is that Anool added an interface to the hacker friendly Fastrax UP501 GPS reciever. We think we have found a winning combination: for processing an arduino compatible ATMEGA328, a micro SD for massive amounts of storage, the ChronoDot (macetech.com) compatible DS3231 real time clock and finally the UP501 GPS module. This board also has on board voltage regulators for both 3 and 5 volts and plenty of break out pins for hackablity.
The initial application is a GPS disciplined timing reference that acquires and maintains 1 microsecond timing accuracy. This even works in the basement of my house! When the GPS signal is lost, the RTC maintains 1 millisecond / hour accuracy on its own. I know that for many DIY apps this is overkill, but we are building a race timing system that requires this level of accuracy.
But why stop there? With GPS in hand, we can determine the timezone! This sounds like a piece of cake, but turned out to be a pretty tricky problem. There are literally thousands and thousands of individually defined timezones! In fact there are 27,732 defined in the generously provided shape file by Eric Muller at http://efele.net/maps/tz/world/.
The good news is that I found a Java library that looks up time zone by GPS fix, the bad news is that they wanted $2000 for it! With Eric’s shape file in hand, and an open source shape file library written in Python only one more piece of information was missing: the list of GMT offsets which was thankfully provided by Wikipedia.
We had an internal debate here at WyoLum. Kevin Osborn found an elegant solution based on zip codes that worked for the United States but was not easily extendable to the rest of the world. While driving to work last week, I realized that we could easily store the timezone for every single latitude and longitude in a fine grid over the Earth on the SD card. And why not? With a measly 1GB SD card, the I2GPS has way more memory than processing power.
Within an hour I had a function (albeit non optimized) that could look up the timezone for any latitude, longitude pair. I guess that answers the make/buy decision that the propriety code begged me to consider. Within 5 hours I had a database of latitude, longetude, timezone, daylight time that was about 22 MB in size. Large for a micro, but fits with ease onto a 1GB card. I used 1 degree latitude bins and 0.1 degree longitude bins for about 648000 points.
For implementation reasons I broke the large file up into manageable chunks by latitude and put them on the micro SD card. Finally I wrote a lookup routine for the micro controller that looks up the timezone by latitude and longitude.
Aahhh setting your awesome word clock for daylight savings time is so yesterday…
Code and hardware will be available soon.