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OGN Cube Control Is Out!

It did not take that long to push the application to the Android Play store (thank you, Petr!) and hence I can proudly announce the OGN Cube Control app is now available for download!

Presently you need to be online to fetch the firmwares while they are not stored anywhere in the phone. Though, offline storage for people without a data plan (like me) is considerably high on the todo list.

OGN Cube Control

The dry February in conjunction with forthcoming season kicked me out of winter dormancy and resulted into unexpected programming hyperactivity. The idea, or rather necessity of an application which could update firmware in the Cubes outside my lair wirelessly and seamlessly was forcing its way for quite long time.

I had already started with its development the previous spring based on my somewhat limited experience gained from programming the Outlanded and VFR Manual apps some years ago. However, this has been disrupted after several weeks due to hitting a dead end. Some communication problems with bluetooth devices originating from my probably deep misunderstanding of the Java-based Android API made me to suspend the app development indefinitely . Approximately six months later I circumstantially participated on Brmo conference where some weirdly-looking and talking chap was demonstrating cross-platform mobile development based on Flutter and Dart. It looked kinda neat, straightforward, simply made a very positive impression on me. All right, I really loved it! But another four months have passed till the day when I finally convinced myself into FINALLY MAKING IT! And that day has happened to be circa 96 hours ago..

I have spent 14 straight hours on Saturday, 12 on Sunday (I seriously needed to eat something), 4 hours on Monday night and 4 more today morning and now can boldly announce that it WORKS like a charm! πŸ™‚

It still needs some polishing but we already plan to publish it it into the Play store very soon so you guys and gals can upgrade your lovely little trackers to the most recent firmware there is! πŸ™‚ The other features like logbook or flights overview will come out a bit later.

Big Trouble with LittleFs

Full track recording is one of the nice-to-have functionalities of the CUBEs. The problem here, however, is that the SD card which is used to keep the data gets easily damaged as data flushes to the FAT filesystem cause considerably high wear, especially in the file allocation table (file size & last modification time). The latter could be avoided by disabling the last file updates time in code. Still, the file size and number of sectors allocated is updated every time a block is added to the file. Keeping the data in memory and flushing in larger chunks may seem to be obvious solution, but when taking the MCU’s RAM size of 20kB (while a lot is already allocated) and FAT sector size of 512B into consideration, one can see there is not much maneuvering space.

Hence, the LittleFS seemed to be the perfect solution. Power resilience and wear leveling make it an exact fit for this troubles until you realize its code base is over 4000 lines and make it considerably spacious after compilation – 8KB, even when forcing size optimisation and omitting unused routines in the compiler settings.

In combination with the pending problem of the rest of my code being already a tight fit into the F103CB’s 128kB FLASH (there is also a custom 8kB bluetooth boot loader for firmware updates), the size of resulting binary with LittleFS included has reached the point it does not fit into the program memory space.

Well, what now? There are two options. The first one is to use an F103 MCU with more FLASH like the STM32F103RB. The catch here, are its 64 pins on the larger footprint while the current PCBs is layed-out only for 48 pins of the CB variant. And as I don’t really want to be redesigning the PCB at this moment another option seem to be quite feasible – to replace the MCU with another one. The nice thing with STM’s controllers is they tend to have compatible pinouts. And as I already have some supply of STM32F030CCs in my drawer (and have big plans with that one in another project), this one seem to be the right fit for replacement. It’s got 256kB of FLASH and 32kB of RAM (comparing to 20kB of the F103CB). Some of the libraries I use will have to be extended to support the F030’s architecture (ARM Cortex M0 vs. M3, the buses and peripherals are organised in a bit different manner) but it would keep the footprint small while opening the opportunities for further development! πŸ™‚

But as things never can go easy, there is another problem. In the recent months the Standard Periperal Libraries (SPL) are for some reason not available for download for the System Workbench for STM32 (sw4stm32) and I cannot make it work even when downloaded them manually from the STM’s web. I have reported the problem on the openstm32.org forum already in two posts (the first, the second) with no success so far. Even the SPL firmware for the F103 doesn’t work now for me.

(Edit) I’ve eventually found a workaround. It’s crude, but it does the job! πŸ™‚

(Edit2) Here you can find backup of all STM32 firmwares that were still available from the stm32targets.xml file.

CUBE3s Available for Ordering

Few weeks ago I had silently added the Choose & Buy option in the menu above but somehow forgot to announce that aloud. I have just noticed mu last post is from April and since that time this site looks kinda dead. But I am telling you – it is NOT! πŸ™‚

We have made twenty five more Cubes (yes another 25!) and those are now being shipped around the world! I wanted to speed up the production process a bit, hence this batch is partially machine-populated. This helped significantly but not as much as I hoped – mainly due to my mistrust and doubts – which were, again, completely unnecessary as it turned out in the lucky end.

I plan to write a longer post about this endeavor later on – a story about going to small production without any prior experience. Yet, the season is on, let’s do some soaring first! πŸ™‚

A LOT of Cubes

Long time no see, right? Over the last month I have been busy with some modifications on the PCB (oh snap!) as well as parts ordering, sorting, reordering missing ones, soldering and finally enclosure printing in order to finish a bit larger order of these little sweet boxes.

As thorough testing is part of the process I have been driving this load around the county for some time. I only wonder what the passersby might have been thinking.

All units passed with flying colours and hence could be nested into their new home.

Do you love it as much as I do? Great job, Ibisek, great job indeed! πŸ™‚

First Two CUBE3s Are Out!

The great day on which two units equipped with three-axis accelerometers and new flight-logbook recording feature have finally reached their happy owners. The first one is about to start its fruitful career in a Piper 28 while the second found its home in an (to me) odd-looking Morane-Saulnier MS.880 πŸ™‚

Despite their confusing micro-USB connector they can be powered directly from the 12V power rail (4 to 15V to be exact). Naturally they sport all the sweet features like the previous development stages – here I’d like to highlight bluetooth communication delivering surrounding traffic information, over-the-air updates and logbook downloads directly to an Android-based phone or tablet (the app will come later, I promise πŸ˜‰ ).

Currently I’m experimenting with various models of the enclosure: from the top – slim (for simple micro USB-power, 17mm of height), regular (RJ45, 20mm) and finally a thick boxes for the battery-powered variant (24mm).

Back on Track

Are you familiar with saying “I have a friend who has a friend..?”

I have a friend who has a friend who can solder.. and I mean really, really well! Using a microscope in combination infra-heating chamber he managed to solder that tiny 3x3mm chip with 24 (no-)legs and it works in all three specimen he produced. I have never seen such a great and clean job before! Awesome!!

It’s so delightful! Just look at that beauty!

This also means we could verify the PCB design is correct and thus we can start truly “massive” production. Even after some had indicated they have no use for such a lovely accelerometer and wish the board to be unpopulated in that spot (complications, grrrr!) But for the other not-so-blindfolded individuals I presume this would be a nice to have extended functionality πŸ™‚

Stay tuned as further detail on OGN CUBE3s build will come shortly!

Soldering Hell

Soldering of the U8 chip went exactly as anticipated. Having spent already more than 10 hours and damaged three chips this job seems to be unreasonably hard.

The QFN24 package is just 3x3mm with 0.2mm legs. Actually they are not legs, there are L-shaped surfaces below and partially on the side of the chip. I’ve already discovered the right amount of soldering paste, the chip seems to be right in place and all the visible side surfaces seem to be soldered just right only the chip does not respond. The design seems to be right and I measured the contacts to be just fine on both sides the chip and the micro. It is still possible I had it overheated during the soldering as I was getting pretty upset at the end of the day..

The rest of the board seems the work as intended, especially the new switched DC-DC step-down converter makes me particularly happy. You can also spot the new super-capacitor (C10) backing up power for the GPS receiver.

There are three different designs on the board – the 12V-powered model “A” with micro USB connector (as you can see here), battery powered model “B” (depending on which parts are populated) charged by the same uUSB connector and model “A” with RJ45 socket for which a large cutout in place of the uUSB (P7) is made (that needs to be made as a separate PCB).

Right – now just to find a way how (or someone) to solder that bloody U8 and we can fire up the wheels of a production line! πŸ™‚

OGN CUBE 3 Prototype 1 PCBs

It is mid January I finally got the message they finished my PCBs so without any thought of hesitation I left my work in mid day and I hurried to pick them up right away.

Top view
Bottom view

To be honest I am a bit frightened of the U8. Obviously not the chip itself but of the soldering fun (I really mean hell) to be expected..

OGN CUBE 3 Prototype 1

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 πŸ˜‰

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! πŸ™‚