Showing posts with label compute module. Show all posts
Showing posts with label compute module. Show all posts

Tuesday, September 5, 2017

Updates: Intel Joule, LoRa, Arduino and Protocase

Blog Break

It has been a while since I posted a blog entry.  I have been knee-deep in a challenging internal project and haven't had much time to come up for air.  Today, I've got a chance to reflect on some of the things that have been happening here at Gumstix and share my perspective with you.

First, there's the EOL announcement from Intel that blindsided the x86-focused IoT community:
 the Joule, Edison, and Curie modules are soon to be no more than a footnote in the history of embedded computing.

Also, Just recently, hardware support for LoRaWAN was added to the Geppetto module library and 3 LoRa boards were released.  I got to play with that quite a bit.  It also brought with it an ATmega32U4 Geppetto module, supplanting the Curie module as our primary Arduino-compatible MCU.

Finally, I've been talking a lot with Protocase.  These guys are cool.  They provide design and production services for custom small-run enclosures, rackmounts, brackets, and consolets. I'm very excited to see what they're making for me.

Intel EOL Announcements and Me

I'll admit it, I took the Intel Joule news harder than maybe I should have.  I spent a lot of time working with it and it's carrier boards.  I was looking forward to putting the GadgetDrone in the air with the AeroCore 2 for Joule, the Caspa HD and one of the RealSense point cloud cameras we have at the office.  I liked the idea of setting up my Workstation board in a 3D-printed enclosure as a Yocto build slave.  Oh and I still hope to test the Caspa 4K's "tone-mapping (Er, I mean HDR) Video" mode.

I was also sad to see the Curie go.  Working with our Radium 96Boards IE board is a lot of fun.  It had been a while since I'd worked at the MCU level.  Bare-wire programming on an 8051 and using a dual-Arduino Uno plus ZigBee robot controller were highlights of my academic career, but I haven't done anything of the sort since.  The Radium's nice and small, IE compliant and has all the cool features of the Curie, like Bluetooth, 6-axis IMU and Neuron pattern recognition nodes.

For whatever reason, Intel decided to terminate their IoT-targeted endeavors.  Maybe it was the slow - and sometimes negative - response from the community.  It's also possible that the challenges in providing software support for their hardware were more monolithic than anticipated.  Either way, the Joule, Curie and Edison are gone.

For all of you who jumped on board with Intel's IoT hardware just over a year ago, I empathize with your plight.


If you're into IoT, you may have heard of LoRa, LoRaWAN and the LoRa Alliance.  It's a communication protocol for sub-GHz long range LPWANs, and it's sweeping Europe and North America's IIoT industry.  It works like this:  

You set up a Gateway. This is the equivalent of a WiFi router in your home, but the difference is these things can have a range of up to 15 km, depending on the quality of your antenna.

You deploy nodes.  These are your data acquisition points - temperature, presence detection, air quality, etc.  Whatever you need to know.  Put them where they need to be and hook them up to a battery, solar panel or hamster wheel (No hamsters were harmed in the writing of this blog post).  The idea is that they require very little power to run and can last anywhere from a week to several months on a single charge, or indefinitely with solar.  These tend to have a range of 2-5 km.

You monitor the data and use it as you see fit.

Gumstix released a gateway/concentrator and a transciever module in Geppetto, as well as a gateway dev board for both the Overo and the Raspberry Pi Compute Modules (Overo Conduit and Gumstix Pi Conduit boards), and a weather station sensor board (Strata Node).  They're in the store and available in both North American and European frequency bands.

Once I had my Gumstix Overo Conduit gateway and an RHF0M301 gateway/concentrator module in hand, I was impressed with how quick and easy it was to set up on  The Strata node I recieved was pre-release and hadn't had the bootloader flashed yet (they come pre-flashed now), so it took a little longer, but writing a sketch and setting up a project on TTN and went super-smoothly.  It just so happens that I made a bit of a quick-start video:

Arduino Stuff

Arduino is a great thing.  For artists, makers, inventors, amateur developers, and teachers, it's a great way to avoid the challenges of bare-wire programming and get physical objects doing what you want them to do.  For professionals, it's a good prototyping tool, delivering your proof of concept to the project manager in hours or days instead of weeks (or worse).

Adding the ATmega32U4 to the Geppetto library means I'll get a lot more time to play with Arduino hardware, projects, board support, and the IDE.  It also means that there will likely be more Arduino boards coming to the store and hardware modules coming to the Geppetto library.

I'm also going to have to find a quick and easy way to set up my 'arduino_pins.h' file.

Discovering Protocase

If you've seen my previous posts, chances are you've seen my low-tech enclosures, mounting brackets and test environments.  My indoor quadcopter test flight had a paracord tether tied to the rafters so that I didn't give my co-workers a hair cut.  I like to think of it as ISRU (In Situ Resource Utilization).  However, in some cases, a solid, well-made case is more than just a good idea.  When I went shopping for enclosures for my Overo Conduit board so that I could deploy it outside, my boss pointed me to  I think he just wanted me to stop asking for a 3D printer for the office.

These guys are awesome.  They're working on something for me and I can't wait to show it off.  They have a huge variety of custom products: L-shape, U-shape 5-sided, milled aluminum, and more!  They'll build from your CAD drawings and have free templates to help get started.  They even have their own design software for you to use.  If all else fails, they will work with you and design a fully customized enclosure for your device.

If you've got a prototype, an invention or a first-run for a kickstarter campaign, Protocase might be for you.  Just check out their page and see for yourself.

To Summarize:

I've been busy.  From grinding away at that internal project to working on LoRa and Arduino board support to designing enclosures to recovering from the Intel IoT fallout, I've hardly had enough time to catch my breath.  Now that things are settling down a bit, I am looking forward to spending more time telling you all about the cool stuff I'm working on.

Friday, March 17, 2017

Gumstix Pi Compute Boards are CM3-Ready

If you follow me on twitter (@gstixguru), you might know that I recently ordered an RPi CM3.  Lots of people have been contacting us to find out how well our Pi Compute boards support the new, faster module, so I found a bit of time to play around with it.  I'd worked with the original CM on our dev board for my GPS and RTK project a year ago with great success, and was looking forward to getting back to the Pi Compute boards.

First Steps

As always, my first step was to flash a brand new image onto the CM's eMMC.  I downloaded the latest Raspbian Jessie Lite ISO and mounted my CM on a Gumstix Pi FastFlash.  Next, I ran rpiboot, plugged the board into my USB hub and CROSSED MY FINGERS!

RPi CM3 on a FastFlash getting flashed. Pardon the clutter.
So what happened next?  Exactly what should:  the eMMC was mounted to my file system like any unpartitioned flash drive would be.  So I dd'ed the image, moved the module over to the Gumstix Pi Compute Dev Board and got ready to Pi.

First Boot

At first, all I wanted was proof of life.  That and I was sure the default wpa supplicant and network interfaces config would not get me on the WiFi network.  So I screen'ed in and powered up the board.  And yes, the console came to life, spewing forth those familiar Linux startup messages.  No kernel panic, no errors, no problem.  So far so good. Raspbian Lite was up and running.  Oh, all the things I should test: GPIOs, I2C, SPI....  BORING!

Let's start with USB (Oh, and get the WiFi up and running while we're at it; screen is not my friend and SSH makes me smile:).  The WiFi dongle goes into the port and lsusb shows a list of devices.  And there it is.

Bus 001 Device 002: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter

Beautiful.  I fix up /etc/network/interfaces and add the office WiFi network to wpa_supplicant.config and shut it down.  Time to set this asside and get back to my other tasks.

Day 2

Before ditching the USB console connection, I have to go into raspi-config and enable the SSH host, and reconfigure the daemon:

sudo rm /etc/ssh/ssh_host_*
sudo dpkg-reconfigure openssh_server
After a restart, ssh works fine.

Let's got straight up the food chain to the camera!  That's what I want to see!  I want to get that Sony IMX219 taking stills and recording videos.  I want to see those LVDS signals in action.  The CSI-2 camera connector is by far my favorite feature of the dev board.  So while I was in raspi-config, I made sure to enable the camera as well.

Here's my Frankenberry Pi camera rig, ready to go, I hope.
So I hooked it up, fired up the module and... nothing.  Did I forget something?  Of course I did! I needed the device tree overlay blob for the camera.  Oops.  OK, so I grab the binary, -- I get the one for both camera and display, just because I can -- copy it to the boot partition and restart.

And did it work?  See for yourself:
Me and my clipboard.
Edit: Here's me trying to pretend I'm not being recorded by the Pi Camera:


I also took a few minutes and got the USB-Ethernet board fired up, and yes, everything works great.
I am very happy.  Stay tuned!  I have a Raspberry Pi DSI display around here somewhere and I want to get that up and running too.

Wednesday, February 15, 2017

There is Nodana...


For those of you who don't know about the 96Boards open-specification hardware platform, it's a design spec for single-board computers (SBCs) that enables SoC vendors to provide their hardware in a standard form factor for increased compatibility.  It's also an engaged community working together to develop applications, software, and mezzanine cards for this ecosystem.

96Boards now has 3 different specifications for 3 classes of application.  There's Consumer Edition (CE), with standardized breakouts for both high-speed and low-speed signals, USB ports, HDMI, and so on.  There's also the Enterprise Edition (EE), which is more for server and networking applications.  It's a larger and more free-form design, with a low-speed header, USB and Ethernet, minimum 1 GB DRAM or expandable SODIMM slots, and optional 1 - 16 x PICe.  Finally there's the brand new IoT Edition (IE) spec.  It's designed to be tiny in order to fit anywhere.

All of these specifications have variants that allow hardware developers to add extra bits to their boards, making this a very flexible way of standardizing the important parts of SBCs.

The big benefit is that you can unite developer communities accross platforms.  The mezzanine card or maker project developed for board A will be compatible with board B, and vice versa.  With support from Linaro, providing a common Linux ecosystem for these boards, not even software compatibility should get in your way.

My honest opinion is that this open specification is very cool.

Gumstix is a 96Boards Partner

Yep, we're in cahoots with the folks at 96Boards and Linaro to bring you compliant hardware.  The release of the AeroCore 2 for Dragonboard 410C was only the start.  At the same time, we added the 96Boards Mezzanine Connector module to Geppetto D2O's library so that users can design their own mezzos for other applications.  If you don't know what Geppetto is, you can learn more by going to the Meet Geppetto page, read my earlier posts, or go straight to and give it a try.

I did a demo for 96Boards OpenHours, hosted by Mr. Robert Wolff (@sdrobertw) and actually flew my MAV, using a Dragonboard and the AeroCore 2 live in my office -- complete with a visit from the "demo demon".  The whole thing's on YouTube.

...Only Joule

So for those of you who don't know, a little compute module was released last year with quite a lot of juice hidden under its heat dissipator. The Intel® Joule™ module delivers unprecedented compute power in a tiny package.  From its two 100-pin Hirose connectors pour USB 3.0, MIPI LVDS,  PCI Express, HDMI, and a lot of what you already expect from COMs and SoCs.  It also houses its own WiFi and Bluetooth hardware.  All with the power of a quad-core processor akin to the Core-I7s you find in your desktop PCs.

Surprise, surprise, Geppetto's got that too!  You can go in and build your own host board using the Intel module and harness most of what it has to offer.

So a Square Peg and a Round Hole Walk Into a Bar...

On one hand you have this fantastic open spec hardware platform [round hole].  In the other, this epic compute module [square peg].  "those will never fit together," you might say (in fact, one 96Boards community member did).  Well, we gumstixians are very resourceful.  And the spec doesn't restrict the SoC's architecture to ARM, that's just the expectation.  So what did we do?  We took all of the components that make the 96Boards Consumer Edition spec great, we wired it up to the Joule connectors, (tested it), gave it a name, and unleashed it on the unsuspecting masses.

And that is how the Nodana 96Boards Consumer Edition (96BCE) for the Intel Joule module came to be.  Here it is:

Gumstix Nodana Features

The Black Sheep

That's right, all you doubters.  Now you can test your 96Boards projects on a powerful 64-bit multi-core Intel chip.  It's the first of its kind -- the first non-ARM 96Boards device.  Take it for a spin and tell me about what you do with it.  You can order it at

x86 IoT Fun

Psst!  We are also taking the IE spec to this dimension.  Our Radium 96BIE board complies with the 96Boards IoT Edition specification and runs the Intel® Curie™ module.  A 32-bit Quark processor  in bed with an ARCv2 MCU, a 6-axis internal measurement unit (IMU) and an independently programmable Bluetooth controller. Check it out at

Monday, September 19, 2016

A New Board and New COM Connector in Geppetto: TechNexion PICO-IMX6

Some of you may be wondering why I haven't posted any updates with respect to my RTK project.  Well, truth be told, it's been pretty busy here at Gumstix.  The release of Intel's new 64-bit IoT compute module at IDF, and our recent induction as manufacturing partner with 96Boards, gave me a steady flow of work.  And now we've released a new development board for the TechNexion PICO-IMX6 COM.

NXP's i.MX6 SoC has a fantastic selection of features - from 1080p HDMI to Gigabit ethernet, PCI express to image processing - and TechNexion has done a fantastic job of breaking out these features in a compact, low-profile compute module, complete with on-board WiFi and Bluetooth, an Edison-compatible low-speed header and two high-speed expansion headers.

Gumstix has put together a board with a long list of features to help you get going with TechNexion's PICO-IMX6 COMs.  Here's a list of its key features:

  • HDMI connector
  • Dual USB 2.0
  • microSD
  • Gigabyte Ethernet
  • MIPI DSI and CSI2 connectors
  • Audio in/out
  • NewHaven 4.3" cap-touch LCD connector

These and several more features, packed onto an 11x8cm PCB, make this board developer-ready for all kinds of projects such as handhelds, home automation control, tiny workstations or home theatre applications.  It's available now in the Gumstix Store

If you like the Gumstix PICO-IMX6 expansion board but it's missing something, or you just don't need this header or that display for your application, Its Geppetto design is available on the "Designed by Gumstix" tab in GeppettoD2O.  You can re-position, remove and add board modules to match up with your needs.

Tuesday, August 16, 2016

Big News From the Intel Developer Forum

The Big News

Intel just announced a new compute module for IoT, pro makers, hardware startups.  It's a big deal and Gumstix brought Geppetto to the party.
The Intel Developers Forum is in full swing in San Fransisco and during the keynote demonstration, the Intel® Joule™ module was introduced to the world.  This thing is a powerhouse!  It boasts a quad-core x86-64 processor at 1.7GHz, 4GB RAM, and up to 16GB on-board storage.  this, plus UEFI-capable bios, 1080p HDMI, two-lane PCI Express 2.0, and USB 3.0 and 2.0 give this tiny 20x40mm compute module the power of your massive desktop workstation.  In fact, you can see the Gumstix Workstation for Intel® Joule™ in action at our booth at the IDF!

Gumstix and Geppetto there for Intel® Joule™

That's right! We are there!  A connector module for Intel®'s new compute module is already available for your Geppetto board design and we are demonstrating it for you right at ground zero.  We have already designed six boards for the Intel® Joule™ and have brought some of them with us to show you.  Now, I won't be there but I and my partners in crime will be introducing Geppetto and the Intel® Joule™ module connector to booth visitors via telepresence.

All six of our boards are available in our store.  Take a look at the current selection:
The Gumstix boards for the Intel® Joule™ module 

If You're There, Come Visit Us.  If You're Not There, Come Visit Us

We want to show you what Geppetto can do.  The boards we brought with us were Designed by Gumstix in Geppetto and you can design your own right there in a few minutes.  The whole team is there to help you out and answer your questions.  If you don't happen to be there, go check out and give it a shot yourself.

Intel, the Intel logo and Intel Joule are trademarks of Intel Corporation or its subsidiaries in the U.S. and/or other countries. 

Thursday, June 30, 2016

RTK Rover Project Chapter 4: Final Stages

Well it's time to wrap up the RTK project.  My rover is driving nicely. I now have a Pre-GO, Pre-GO PPP, WiFi antenna, 4x AAA battery pack and my motors connected to my Gumstix BBB Rover cape, And my Gumstix Pi Compute Dev Board is rigged with my Pre-GO PPP SMA and antenna, as well as its own battery pack.  I have not, sadly, finished my automated driving software, but that's going to be a little time-consuming, so I'll stick with what I've got.

The Plan

I am going to simultaneously track my rover with RTK, PPP and standard GPS as it circumnavigates one of the tennis courts.  I'll be steering it from my laptop, logging the raw datastream from the two GPS modules with the BBB and the RTK solution data by way of the RTKLIB Windows tools on my laptop.
Then I'll plot the data and share it in my next post.

Sadly, the skies aren't co-operating today so I'll have to put the experiment on hold until the weather clears.

The Hardware

Now that I have everything assembled for the final experiment, here's a manifest of the primary components I used and where you can get them:

This is what it looks like all put together:

There's only one GPS header on the Rover cape so I had to solder the cable for the second Pre-GO directly to the BBB connector header.  Now it looks like this:

The Software

You can check out the git repository at:

I'm only using RovCtl for this experiment, but I intend to finish my automation software somewhere down the road.


 I have to admit I've been testing my rover control software a bit more than necessary.  Honestly, how can you resist driving a little robot all over the
office, chasing co-workers to the coffee machine, etc.  For kicks, I taped a camera to the bot and recorded my shenanigans.

I think the BBB's batteries were running low.  There were a couple of moments when there was noticeable lag between command and response, but I still managed not to hit anything too hard.  With a full charge and some clear weather, we'll have this experiment wrapped up in no time.

Check out the video above to see how it did.

Up Next: Results!

Friday, June 10, 2016

RTK Rover Project Chapter 2: The Early Development Stages

I am working diligently on my RTK project and have hashed out a lot of the details.  I've made progress in software, my hardware is on the way, and some of the specifics have been hashed out.  Here's my progress.


RTKLIB is not a trivial API.  Coding an automated base-station / rover application from scratch would take more time than I can dedicate to this project.  So I have taken the two apps that pertain to my needs and have begun making modifications to them.

First off, I need a background communication channel for instructions from the base station and data from the rover.  The easiest way to do this, of course, is to set up a TCP socket.  Str2str, an app that takes the data stream from your GPS device, converts it into a universal format and redirects it, uses sockets to stream GPS data between rover and base, but its use is obfuscated away in the depths of the library and isn't configured for secondary data structures. Likewise with rtkrcv, the rover-based workhorse that interprets the SNR data to get a hyper-accurate fix.

What I've done using a very straightforward abstraction layer for the standard gnu-sockets library, Simple Sockets, is built a back-channel for data from the rover's IMU, as well as its precise coordinates (which I am well aware I could get for free from rtkrcv, but would have to cherry pick. Besides, I may as well retransmit it to where I want it since I need the second socket port anyway) to the base station, and for waypoints for the rover.

I also removed the console for rtkrcv. This won't be necessary as the base station will issue all the required commands to the rover.

The next step is to make this whole thing ARM-compatible and set up some makefiles.  The makefiles are easy, even if my format is a little naive.  I don't have a lot of experience in writing them so they're fairly verbose and don't use much in the way of macros or regular expressions.  Now that the build process is nicely automated, I need it to cross-compile.

There were a few compatibility issues, but most of them were solved by installing or updating glibc.  The worst transgressor of all was Simple Socket's use of vsprintf() to collect and format a list of arguments into text.  The problem is the function requires a list of arguments of arbitrary length.  something along the lines of:

foo(char* format,...)

I replaced vsprintf() with sprintf() and so far it hasn't broken anything (fingers crossed).

Now it's cross-compiling and running on both the BeagleBone Black and RPCM.  Next step is getting motor control and IMU data working.


A couple weeks ago, I ordered this robot chassis and this motor driver from The chassis was on backorder so my shipping date got pushed back but I got an email this morning and my equipment is en route.  I also grabbed some 4-cell AA battery cases and barrel connectors from DigiKey for my two boards and I have some NiMH and LiPo cells to choose from here in the office from previous AeroCore 2 tests, which will work well for powering the robot's motors.  I've considered adding IR proximity sensors for obstacle avoidance, but that's just icing so I'm going to skip it, at least for now.

The Plan

Here's what our autonomous robot will do. It will receive waypoints from the base station and, using the magnetometer, it will navigate to that waypoint.  As it moves, It will transmit its coordinates, including altitude, to the base station along with its heading and pitch from the IMU.

A motivated individual (potentially myself later) would be able to generate an accuarte 3D mapping of the terrain the robot traverses.  Kind of sounds like a good surveying technique.

Up next: robot and data test!

Friday, May 20, 2016

RTK Rover Project Chapter 1: RTK and RTKLIB

Not long ago I posted about getting the Pre-GO PPP GPS modules up and running on BeagleBone Black with our Gumstix BBB Rover cape.  Now that I have them working on both this and the Gumstix Pi Compute Dev Board, it's time to take the GPS fun to the next level.  So what can we do with two incredibly accurate GPS modules running on tiny devices?  How about Real-Time Kinematics?

RTK eliminates the jitter experienced by solitary GPS receivers using differential techniques.  It requires a base station with known co-ordinates and a mobile reciever. By using the difference in signal-to-noise (SNR) ratios and phase for common satellites, RTK algorithms can cancel out atmospheric effects that can pollute geopositioning results.  I won't go into incredible detail here since Navipedia has a great wiki on the subject.
This image shows the GPS/GNSS data in pink and the RTK results in green of a rover driving around in a  6-meter circle.

So why do we care about RTK?  It's primarily used for surveying, but there are many situations when a robotic rover may want to track its path, report its exact position or navigate to a given waypoint with a high level of accuracy.  That's what I'm excited about.  I'm going to rig an automated robot with a BBB and Rover cape, use my RPCM rig as a base station and use the GPS data to control the rover.

First we have to get some RTK software up and running.  There aren't a lot of options for this in the open-source world, but the biggest name is RTKLIB.  It's not only an open source library, but it also includes a complete set of GUI and CLI apps to get you started.

Sadly, the GUI elements are written for Windows, so there's no chance of using them on the Pi Compute dev board, and I'll have to monitor operations from my laptop.  But the str2str and rtkrcv command line programs are the two most important elements of the software suite for my needs. these applications, and eventually their source code, will be the backbone of the RTK project.  The easiest way to compile these for ARM Linux is to download the source code onto your BBB and Raspberry Pi and compile them natively.  I ran into a little linking problem after I cross-compiled the applications on my PC and tried to run them on the COMs.  In the end, it was just far less hassle to go native.

Having set a precedent with the Gumstix Pi Compute Pre-GO PPP project, I felt I had to build a fancy box for my Gumstix BBB Rover.

I got the COMs equipped with their expansion boards, Pre-GO PPPs and antennas and wrapped up in a nice package.  With the RPCM being my base station, I used a Pre-GO PPP SMA so I could use a more sensitive antenna.  This will get me a more accurate fix on the rover's position.  The antenna I'm using is the Dominator AA.161 from Taoglas.  The BBB Rover has an on-board TI WiLink8 WiFi and Bluetooth modem that requires a u.FL antenna, and I'm using the Pre-GO PPP with the built-in antenna.

With the binaries and data files on the boards, I started experimenting, streaming data from the COMs to my laptop and trying to get a fix.  I tried a myriad of config files and, after some digging, I put together this file. The commands therein are transmitted to the u-blox NEO-7P on the PPP boards and instruct them to transmit tuples that are normally blocked across the UART channel.  These strings carry the phase data of the satellite signals which RTKNAVI, the GUI I use on my laptop, uses for RTK solutions.

After some trial and error, I began to see SNR data.  It looked something like this:

The top graph is the data from the BBB, and the bottom from the RPCM.  Each bar represents the SNR from a satellite.  In order to get a solution, the two computers have to be able to get a strong fix (shown as a colored bar) on several common satellites.  Unfortunately, the window in the office only provides half a constellation.  Not nearly enough for RTK... Barely enough for a single fix.
My little computers are getting their fix.  Tux is helping.

 Clearly, I need to get outside.  That'll have to wait until next week.  In the meantime, I'm all set up, apart from a battery pack for the BBB, to do some real testing.

NEXT TIME: The great outdoors, differentially.

Monday, May 16, 2016

Gumstix Pi Pre-GO PPP Project Chapter 5

I took my equipment to the tennis court yesterday and gathered some data.  When I arrived, I was saddended to discover that the two main courts were occupied so I went to the last one. Ten minutes at each of the eight corners I'd mentioned before  gave me quite a bit of data.  When I plot it on Google Earth, it looks like this:

OK so something's wrong.  First off, the orientation Google's image is clearly incorrect. Secondly, there's that tree!  It's covering the entire back-right corner!  I might be able to go again some other time, but let's make some observations first.  Looking at the inner corners, [LBS, RBS, LFS, RFS], the dimensions are reasonably correct.

What it looks like to me is that the court sits on a slope, which I hadn't considered to be a major source of error.  I had assumed that the courts would be level but, having been there for some time, they have most likely sunk in places and bubbled in others.  I may have had more luck had I acquired access to Wimbledon,  but the fact of the matter is I'm trying to measure exact distances with chunks of metal free-falling high above the earth and no fixed point of reference on a surface with random elevations.

Here is my conclusion for this project:  The Pre-GO PPP works beautifully with the Raspberry Pi Compute Module through the Gumstix Pi's UART breakout connection. It is able to measure GPS position with decimetre-level accuracy and sub-decimetre jitter.  However, measuring distances with sub-metre-level accuracy is next to impossible using GPS coordinates alone.

There are many reasons.  First off, environmental factors, such as trees and bridges will drastically increase dilution of precision.  Reason number two is explained above.  Lastly,  I can't seem to get enough court time to collect all my data points.

Clearly, a new strategy must be employed.

Up next: BBB Rover and RTK

Thursday, April 28, 2016

The Gumstix Pi Pre-GO Project Chapter 4: Tennis Anyone?

I went to find the survey marker from and discovered that it was directly under a bridge.  It's also in the middle of a road.  I think that the coordinates they're publishing are not as accurate as I would like.  Strangely, there does not appear to be any more markers in the near vicinity of the office.  In the absence of an accurately located marker, I'm going to try and measure the dimensions of a tennis court with GPS data.   
So far, I have been very impressed with the Pre-GO PPP's performance.  I took it out for another field trip recently and had very nice 0-8 cm diameter groupings.  HDOP has been consistently near and below 1.0.  Geodetic engineers and surveyors would be pleased as punch.
I intend  to define the outer bounds of the court and the service lines within.  If I draw a 11x24m box with an 8.2x13m box smack in the middle, the test will be a success.  These measurements are based on the regulation court dimensions outlined in the image to the right.  I'm also considering measuring the accuracy of the altitude measurement.  The net is 1.6m high and if I can get that measurement from the base of the net post to the top, that will be an interesting data point as well.
The difficulty I have faced with my setup has not been the hardware itself.  This has performed perfectly throughout my experiments.  The issue has been with logging and interpreting the data.  I have been using my cellphone as an ad-hoc network router to ssh in to my Pi and during one experiment, the connection between my laptop and my GPS rig kept dropping out.  As a patchwork solution to this issue, I have added a physical connection to the RPi's system console: Just a short USB microB-to-A I can connect to with an extender cable.  If the WiFi drops out, I can just plug in.

Added to this is the fact that, in general, GPS modules spit data out once per second.  The Pre-GO PPP is no exception which means that, for a 1-hour test, there are 3600+ records to process. I'm using Python to interpret and plot the data but it still takes time.
Up next: RESULTS!

Monday, March 7, 2016

The Gumstix Pi Pre-GO Project Chapter 3: I can't Rely on Google Maps.

There was a nice break in the weather yesterday and I managed to get outside to take some readings.  I set up on an exposed hilltop with my laptop, my Pre-GO-to-go and my smartphone.  I was hoping that I might find some kind of survey marker with exact GPS coordinates at the base of the flag pole, but no such luckI fired up my Pi, gave it a few minutes to warm up, and connected it and my laptop to my phone's WiFi hotspot.

With no guarantee of clear weather, I decided to do a quick test and grab four different data snapshots over a 15 minute window.  I'll formulate some more informative tests for when the weather is better.  For now, I just want to see how accurate it is.

The PPP in Pre-GO PPP stands for Precise Point Positioning.  PPP provides centi- to decimeter-level accuracy so, even if Google doesn't drop its pin directly on the flagpole, my data points should be very close together.  I have to assume that Google Maps co-ordinates are going to be somewhat skewed.  Without an accurate geodetic survey marker, I can't be certain.

When I got back to the office, I dropped some pins on the map and here's what I came up with:

The outlier is my initial result.  The tight grouping south west of it are the three other results I recorded.  They sit about 1.5m away from the outlier but are all within 12cm of each other.

I found this blog post that confirms my assumption about Google's geodetic accuracy.  If you compare my Maps screen shot to his, it looks like the skew is about equivalent.  I trust my results over Google's now.

So I still have not concrete baseline measure of accuracy.  I really want to know if my horizontal co-ordinates, when HDOP (horizontal dilution of precision) is less than 1, are accurate at the decimetre level.

To that end, my colleague sent me a link to, where I found a survey marker nearby.  GPS enthusiasts have, thankfully, taken the time to accurately measure its geographic position.  OK great, but I have been rained out.  I guess the next test is going to have to wait awhile.  While we wait, let's see if the Pre-GO works with the BeagleBone Black and the Gumstix Rover cape.

Next Time:  Pre-GO and the BeagleBone Black Rover Cape

Thursday, March 3, 2016

The Gumstix Pi Pre-GO Project Chapter 2: Pre-GO Packaged to Go

So, while we're debugging the UART header, I thought I may as well get some results from the Pi using the FTDI cable. With the help of a USB hub, a WiFi dongle and some masking tape, I set the Pre-GO up on the window.  I figured if I was going to get any kind of signal anywhere in the office, this would be it.

I SSH'ed in and ran gpsmon. This is a great tool related to GPSD that spits out human-readable GPS data in real time.  It looks something like this:

Yep, my Pi kind of knows where it is... within 10 metres, that is.  Not good enough for a Precise Point Positioning (PPP) GPS module.  I have to get it outside to get accurate geolocation.

Good news! The UART problem was resolved with a single line:


I appended this line to /boot/config.txt and said goodbye to the FTDI converter.  With the bulky USB cable and hub gone I decided to get my gear ready for test.

A circuit board with a delicate makeshift UART connection is not easily transported.  Not to mention the need for a power cord makes taking my rig on the road a bit of a challenge.  No problem. Tape, scissors, and a shipping package, combined with a little time gives you this:



Next Up: Where am I, Precisely?

Friday, February 26, 2016

The Gumstix Pi GPS Project Chapter 1: Break it out and get it running

As my first gadget project as Gumstix Guru, I'm going to connect a Pre-GO PPP GPS to a Raspberry Pi Compute Module by way of the Gumstix Pi Compute development board, pictured below.

Getting Started

I could just build a board in Geppetto with the GPS connector on it, but I've already got my Gumstix Pi in hand.  The Pre-GO communicates over a UART connection, a header for which the Gumstix Pi has.  The trick is that I need to manually rig the connection.  Easy enough.  Let's break out the Pre-GO's header:

I made a point of labelling each one of the wires just to make life a bit easier later on.

Of minor concern is the fact that the pitch of the Pre-GO's header is considerably smaller than that of the dev board's UART header so I had to use a finer gauged wire.  Not a big deal but they aren't a good fit for my jumper wires.  My solution?  Easy:  Fold 'em.

Next I decided to forgo the extra mess of jumper wires and go straight to the jumpers.  A nice way of keeping the rat's nest to a minimum.  Oh, and my labels fell off.

First Power-Up

At this point I'm very excited.  The board's all hooked up, the Pi module is in place and it's time to plug it all in.  Hope I didn't forget anything!
Once Raspbian is up and running, I go hunting for my GPS module to no avail.  What's wrong?  Why isn't it working?

Time to go to the test bench to make sure the module works. 
  • Board configured for 3.3V - check
  • Connectors attached correctly - check
  • Waveform resembles data output - check
So I hook it up to an FTDI-UART adapter and check its output.  Looks like GPS data to me:

The Verdict

Okay so the Pi is working and the GPS module is working, they're just not talking to each other.  So the UART header isn't configured correctly.  I'll get that sorted out later.  For now, I'll just hook it up with the FTDI adapter and get some results.

Next Up:  Raspberry Pi CM and GPSD