OGN Cube

Over the Xmas “break” I finally saved some time to amend the schematic and add two new blocks. The first one is switched DC supply to eventually replace the linear regulator and thus save a lot of battery juice when powering the tracker directly from 12V on-board battery.

The second improvement or actually a new feature is footprint for the promised accelerometer / gyroscope on board. There are two solderable options – MPU-6500 or MPU-9250. The guys from Invensense did a reasonable job to put those in compatible package with only one extra jumper to be solder-bridged on the PCB when having populated the latter.

A third tiny gem is a miniature supercap on the backup input of the GPS module to retain last known location (for approximately 12 hours) in case of power outage. It shall be significantly faster than from a cold start!

By routing the board I pushed again my capabilities way farther while putting in all the additional parts and saving space on the board as there were so many of them and the remaining free space was so scarce. Groovy!

A little thing still the bugs me a bit. It is mainly the MPUs are marked as “not recommended for new development” on Arrow and Farnell but hopefully will be still available for some time. And during that time the future will show whether this part is of any use and advantage or completely none 😉

The prototype board has been sent to production on 27th December and shall be finished in mid January. I presume a week later I should know if there are any problems on the board and the design will need some additional rework or not. I hope for the better, of course.

And then, finally, I will have to find someone who will help to manufacture the units because as I said last year – I will never solder so many boars by hand again! 🙂

After  a long break (seasonal, really) I am finally back with yet another good news ~ I have finally saved time and devoted rainy afternoons and many sleepless nights to the long-promised feature – the data logging.

It had had been such a long run mainly due to my initial intention the code must be original, based on “pure” STL and every part must be clearly explainable, no black boxes and fuzzy libraries. Hence, to make the FAT live on the uSD connected via SPI  was  anyhow close to a piece of cake (as obviously is for the other folks our there). There were virtually no clues how to bend Chan’s FatFS library to my needs. Until after a  considerably long desperate days of hopeless searching I have discovered this site which old version contains a treasure box in form of these two blog entries that really made my day. Cheers buddy, whoever you are!! 🙂

After having mastered the FatFS operations there was another riddle to solve – the format in which to store the data. Initially, the .IGC seemed to be a natural choice (and also many suggested so) but as we need to store some more information than the IGC format supports (e.g. acceleration data), this was not the right one. Additionally, the IGC seems to be rather verbose and since there is no plan or vision to make the OGN Cubes certified FAI recorder we do not need the record to be signed and processed in the traditional way. On the contrary, human readability of the recorded files would be beneficial.

For that reason we came to the conclusion a simple CSV file with meaningful header could be the best choice. It can be easily read by a spreadsheet processor, converted to various formats (GPX for example) and the resulting files are of reasonable size also in case of considerably long flights.

You can see an example of selected recording lines right here:

$OGNR;HHMMSS;gpsFix;pressure[Pa];lat;lon;gpsAlt[m];gpsSpeed[m/s];gpsTrackCourse[deg];ax;ay;az*CRC
$OGNR;112332;3;92884;49.860138;17.613463;727;56.4;327.2;0.222;-0.886;1.370*2a
$OGNR;112341;3;92917;49.864000;17.609517;726;57.7;326.6;0.598;-0.640;1.093*28
$OGNR;113317;3;91468;49.898227;17.543775;852;46.2;246.3;0.592;-1.177;1.069*25
$OGNR;114233;3;93324;49.815882;17.234948;686;52.5;78.9;-0.697;-1.389;1.520*3f

As the logging feature is finally in its mature state can been released to the wild. Those of you who have a tracker box with the uSD card slot present will receive firmware update shortly. The update procedure is  as described in the leaflet. You will need to use the firmwareLoader to upload the new binary to the unit from your laptop via bluetooth.

The work on further releases is still not done, however. In the upcoming weeks and months the plan is to implement:

• Android app to download and flash the firmware updates seamlessly,
• to download the flight logs from the unit using the same app so we don’t need to remove and put back the tiny uSD card every time,
• to integrate the accelerometer to the PCB (there is still a lot of work, experimenting and decisions to be made),
• and finally, one day, to add the you-know-whose protocol support.

And that’s all for this time! 🙂

May turned into its second half when a package with so much expected PCBs finally arrived from Apama (a local manufacturer in Brno). During the following weeks they gradually migrated from one box to other, then yet another and back until they grew up and matured to their shiny functioning state.

This is the story how it all happened.

Breaking up the frame into separate little boards was a pure pleasure.

Followed a thorough visual inspection of each piece from its top and bottom side. You know, when electric check is not enough..

First populated power source & MCU. Bringing it to life and also first test of correct battery operation on the second revision of the PCB.

Soldering a single MCU is a piece of cake. Five is still OK. But TWENTY?!

Adding microUSB and SMA connectors.

All SMDs are finally on board – let’s start with modules!

Populating pressure sensors means to solder only 20 x 6 = 120 legs. Easy! 🙂

Bluetooth modules ready for soldering as the next; they go to the bottom side.

GPS and radio modules.

And first fully populated OGN tracker is alive! Hooray! 🙂

They are starting to pile up..

.. till they are everywhere!

Each and every antenna was carefully packed in a tiny plastic bag. Unpack one is a short operation, but twenty of them took some time.

Aren’t they cute? 🙂

Every tracker comes with a tiny but still powerful battery (nothing for the drumming rabbits). The fella in the shop was looking a bit suspiciously when I was requesting 22 of those, asking what do I need so many Nokia phones for.. B-)

And seriously,

It has taken some time but this waiting was worth it. First two prototypes of the Cube TWO have been tested both on ground and in the air and at this moment I can proudly announce they work reliably under all reasonable conditions and thus can be released into the vast airspaces around us! What an announcement, right? 🙂

There are two flavours of the box – one specially designed for competitions with an internal battery. This required to develop and validate a battery charging and protection circuitry which makes it a reason for being so late into the season.

On the device front facing side there is a switch to power the tracker up and down and a micro USB connector to charge the battery from a 5V power source/phone charger. Finally,  there is an indication LED which gives you instant information about state the device is in. The battery capacity is 1070 mAh and lasts for approximately 30 hours when fully charged.

The latter flavour of our tracker is intended to be permanently mounted on board of your sweetheart. It is powered through a standard RJ45 socket which gives you the opportunity to power it directly from your 12V batteries. It also brings the opportunity to control the transmission mode via a three-way switch on your dashboard: normal TX mode, competition mode (with the competition flag set) and finally a TX-disable mode (while keeping the reception on).

In addition to all of this, there is a slot for a micro-SD card to log your flights or encounters for later use. However, this functionality is not implemented yet and this can perceived be this is a preparation for future firmwares.

Both versions are also equipped with bluetooth connectivity so you can see all the information right in you navigation device. The bluetooth interface is also used from relatively seamless firmware updates.

With the upcoming season time has come to present the shiny OGN Cube in second generation. What is new, different and (of course) better?

Firstly, and most importantly – there will be only a limited amount of Chinese components. Despite being so tempting to use stuff with free shipping from the country behind the wall, my experience from the past two years is so dark that I refuse to use them more anymore. But still, I had to bite my tongue and use two of them as procuring them from the reliable sources is impossible (the BMP and the BT).

The obsolete GPS receiver is being replaced by the GPS/GLONASS-capable Quectel L86 module with 33 concurrent channels and antenna with greater gain. Radio module will now be the RFM69HCW and as the barometric sensor the BMP280 is going to be populated.

The back side of the board is occupied by a bluetooth (bt) module with two features. The main are firmware updates (as the only current possibility to do so is to crack the box open and flash the firmware using a dedicated programmer – not very handy in the field). The process is now provided by a python script running on a bt-capable computer but in the near future this will be done using an Android phone (no fruit options!) directly on-line from the web. The secondary (although also primary :)) use for the bt is connection to navigation software to transfer spatial information about other planes in the surroundings.

The second new development on the rear side is presence of a micro SD socket to store flight recordings and who knows what else..

The OGN Cube TWO is designed in two strains – for competitions and for cross country flights. The former is distinguishable by a micro USB connector used to charge the internal (BL-4C / BL-5CB) battery. This battery is a widely known and used Nokia model which can (and hopefully will be for long time) easily available everywhere. The MCP73811T will take care for its correct charging together with all the madness around that clever chip.

The latter variant is a box to be fixed into the dashboard. It connects through the RJ45 jack which is present in all the other device we already have on board. Additionally, it lets you connect a three-pole switch to control the competition mode (do-not-track flag), no-TX and the regular mode.

New board also requires a new box, right? It needs to be a bit bigger than before but will let you to open it for possible tuning, changes or even (unlikely) improvements. There are going to be another two options: a 3D-printed ABS plastic box of various colours and combinations or an sweet aluminum enclosure with possible black anodised coating.

It’s gonna be a piece of art. Stay tuned! 🙂