Homemade GPS logger

[dave windymiller]

Arduino based GPS flight logger - Dave Windy Miller

What follows is quite in depth but hopefully clear enough to someone with a bit of Arduino experience and I can answer any queries you may have!

I thought I would share with you my experiments with a flight logger made for less than £25 that includes GPS coordinates, GPS speed and barometric height.  All this data is written to an SD card that can be read by Google Earth.

 

 

This is my original logger built with a Neo-6m gps module built into a Futaba receiver case and attached to a ply base for attachment into my “Hotspot” turbine jet.   I have since dropped the small oled display.  A smaller version would be possible with a purpose build pcb c/w the processor chip The data is recorded onto SD card and can be subsequently imported into google earth and displayed as a flight path.

Whilst altitude can be obtained from the GPS, ive found this is less than reliable with the altitude changing by 50ft or more just because the satellite count changes!   A BMP280 chip can be set to be zero at the point of reboot and show altitude above launch in feet and is reportedly good for +/- 1ft which is 0.5% error over 400ft but read below re atmospheric pressure effects!

 

 

 

For info:-

Barometric chip bmp280     

The height to pressure response is a curve but for our range of altitudes it is linear for all intents. The barometric pressure affects the readings with a drop of 1mb equalling ~28 feet in altitude. The difference between low pressure and high pressure weather can be equivalent to an altitude change of 2000 ft or more!    Ideally, you would set the barometric pressure and height above sea level each time its used but this is a faf.  To avoid this, I set the height to zero on power up so all altitude change is relative to this point until its reset (as it’s a near enough linear response).

Any barometric changes during a 5 minute fight are generally negligible unless there’s a severe storm looming!  If it drifts negative before take-off (baro pressure increasing), the software resets this to zero so as it stands my software would need a modification if used on a slope soarer flying below you!

 

 

The pressure these sensors detect has to be static pressure and not be affected by the air velocity.  Whilst this is difficult to quantify, mounting the sensor in an inlet duct or in front of a fan impellor for example isn’t a good idea.  If possible, mount it in, say a cockpit that isn’t greatly affected by the airspeed / throttle position.

 

 

The barometer chip I used is a BMP280 although a BME280 will work as will a BMP280/AHT20 dual module (all must be 5V versions).   There are two address for these chips so you may need to edit the line in the code:-

bmp.begin(0x76);   for BMP & BME 280 which is the normal default

bmp.begin(0x77);   for the BMP280/AHT20 combined.

Some are 4 pin and some are 6 pin.  Both work, just ignore the pins not shown in the circuit diagram

Edited March 22 by dave windymiller

[dave windymiller]

GPS module   

Bit of a minefield these modules are.  There are loads of different versions on ebay – Neo6, Neo7 & Neo8’s.  They all seem to work at default 1hz sampling rate but they should be able to sample much faster.  Many don’t remember their settings and default back to 1hz.  Some remember their settings but this info is retained by a charged capacitor and is lost after a few days.   This is down to the modules being low cost and in some cases,  the chips being fakes??  Quite what the full story is re fake chips I don’t know but they all generally work ok at 1hz sampling rate!

Some boards wont allow you to change sampling rates and these are definitely fake being TD1030 gps modules re-labelled (badly – see pic).   Given their cheap price, they do seem to work reasonably well at 1hz however.   

The GT-U7 (Neo-7m based) seems to work well and seems to remember its settings and is smaller.   There are also the newer Neo-8 modules that ebay sell which I haven yet tried but should be ok (if genuine)!  The newest Neo9 modules are less readily available and are more money ~ £30 upwards – again not yet tried one.  

                     

Neo-6m                                                                                               Neo-7m v2

 

                          

 

 

GT-U7 (Neo 7m based – smaller)                              Fake neo-6m. Original sticker outline visible and an uneven surface from old glue!

 

For smaller slower models, the default setting of 1 per second data rate is fine but on a jet at 200mph a long distance can be travelled in 1 second and a path that crosses many other paths during a flight can difficult to visualise on a screen.  

 

 

Interrogating the GPS module using UBLOX software.

Using Ublox software https://www.u-blox.com/en/product/u-center. This software allows you to interrogate the modules (even fake ones) and display live information on its many screens.  It also allows many alterations to its operating parameters such as baud rate, sample rate plus much more. 

Some GPS modules have a USB connector and these connect directly to the usb on the PC with a suitable lead.  If it doesn’t have a usb connector, you also need an “USB To TTL FT232RL FTDI Serial Adapter Converter” (approx. £4) and connect it as shown (make sure its set to 5V on the jumper).

 

FTDI       -              GPS                                                                       

VCC        -              VCC

Gnd        -              Gnd

Rx           -              Tx

Tx            -              Rx

 

Leave other FTDI pins disconnected.   

Once the UBLOX software is running and the GPS is powered up, wait for the GPS to find satellites (LED on GPS starts to blink).  This works inside a house if near a window. It may take several minutes first time round.  Make sure the antenna is ceramic side up and don’t let it touch the circuit boards.

If it doesn’t communicate to the PC, check these settings on the UBLOX software:-

Receiver > Connection  and   Receiver > Port.

You may have to tell it what Com port its connected to (its never Com1) and its baud rate which is 9600 by default unless you change it.

Once communicating, you can play with the software to get a feel of the gps module.  The next bit is for information only as my software does this automatically on reboot but its interesting to play with however.  Make sure the baud rate is returned to 9600 or 38400 if you change it otherwise my software may not be able to talk to it!

 

To alter the scan rate, go to:-

View > configuration view

Look down the list to find “Rate (Rates)” and you will see its set up for 1000ms.  Adjust this to 250ms for 4 scans per second.      Then click “send” button.

Having done this, you need to speed up the comms rate as there is too much data for 9600 baud (data is jumpy and erratic on the screen).  Look down the list to find “PRT (ports)” and you will see its set up for a baud of 9600.  Adjust this to 38400. Then click “send” button.

Finally go to “CFG (Configuration)” and check that the “save current configuration” is ticked and press “send” button again.

You should see the barcharts updating much quicker having done this.

There are many other things to play with but that’s beyond this project and me!!!

 

 

 

 

Edited March 22 by dave windymiller

[dave windymiller]

Checking if your GPS is a fake!

Connect the GPS to Ublox software using an FTDI board and once its communicating, ensure the default 9600 baud is set.

Select View – Text Console and you should see the gps communicating its NEMA messages that look like:-

 

 

You need to reboot the gps whilst its still connected so its easiest with a FTDI board where you can just briefly disconnect the +5v wire between ftdi and gps. Clear the screen of text and reconnect the +5v. and you get something like at the start of the data stream:-

$GPTXT,01,01,02,u-blox ag – www.u-blox.com*50

$GPTXT,01,01,02,HW  UBX-G70xx   00070000 FF7FFFFFo*69

$GPTXT,01,01,02,ROM CORE 1.00 (59842) Jun 27 2012 17:43:52*59

$GPTXT,01,01,02,PROTVER 14.00*1E

$GPTXT,01,01,02,ANTSUPERV=AC SD PdoS SR*20

$GPTXT,01,01,02,ANTSTATUS=DONTKNOW*33

This is a genuine u-blox Neo7m i.e. UBX-G70xx   (note - some fake NEO8m chips are actually relabelled NEO7m chips which are at least 7 years older)  

Or you may get:-

 

$TDINF,Techtotop Multi-GNSS Receiver*63

$TDINF,T3,RomFw,1.1(48),Aug 12 2016 16:57:35*02

$TDINF,GNSS=BDS+GPS,ANT=Integrate*6A

The response from a fake Neo-6m (Techtotop TD1030 processor) which has probably a iffy looking label!

Or you may find the first 3 lines of $GPTXT are missing so you don’t know what it is!

Like I said, even the fake ones work ok at 1hz!   A fake neo8m that turns out to be a Neo7m would work fine even at higher sample rates but its not the point as it’s a misrepresented sale! – send it back!

 

 

 

SD card & card read/write module & Data file   

  

 

 

The 32 gb or less micro SD card has to be formatted to FAT32. A disk of 1gb is more than enough so an old card is perfect.  Obviously, you also need an SD card reader or a converter to USB to get the data onto your PC too.  Around £2.00 from ebay if you haven’t got one!

 

The time-data beamed from space is accurate to fraction of a second compared with a radio time signal clock but the hour is in universal time UTC (same as GMT).  I add an hour in the code so it displays as BST as I’m more likely to fly in summer.  I could add a switch (summer/winter) but decided it was unnecessary.    If you are elsewhere in the world, you can add whatever to the hour code to get your time correct.

The software automatically starts a new file on the SD card each time its rebooted. These are named “Data00.CSV” up to “Data99.CSV”.  After 100 files, you need to wipe the card for it to write again.  The raw data can be read by a text editor or into Excel as it’s a .CSV file (comma separated values) which means each data item is separated by a comma and Excel starts a new column.

 

Below is a typical data file taken from car ride up a hill sampling at 4hz (0.25 second intervals) hence the 1/100ths column showing steps of 25.

 

When the datafile is “ingested” into Google Earth the data can be visualised and coloured to suit e.g. for height, speed, time etc.  Height can be visualised with vertical bars. In the first post theres a pic of my jet taking off at Buckminster last year (at 1hz).   I will explain how to set up Google Earth later.

 

[dave windymiller]

Making the GPS unit

I will describe the latest version which consisted of :-

1)      Arduino Nano   £3.50                     (CH340 versions need ch341 driver loading onto the PC 1^st - https://www.wch-ic.com/downloads/CH341SER_EXE.html )

2)      BMP280 board  5V                            £3.50   (either 4 pin or 6 pin version but must be 5v)

3)      SD card read/writer board  5V    £2.50

4)      Neo7M  c/w antenna                      £8.50   

5)      Veroboard & wires

6)      SD card 32gb or less (fat32 formatted)

My module was powered by a 400mA AAA NiMh and will run all day on one charge. Ive tested it down to 3.5v so could be powered from a 1S lipo, balance lead or 3 cell nimh!  I recommend that the power source is independent from the Rx battery for obvious reasons!  

I used Veroboard with the tracks cut using a drill bit and wire links added to achieve the circuit as shown below.   I only soldered in the pins required on the Arduino Nano rather than all of them which simplifies things.  If you add wires to run underneath the Nano, make sure they are insulated to avoid risk of shorting to the Nanos underside.  

A 4.8v to 3.8v supply can be used as shown but its also possible to connect 6-10V to pin “Vin”.  The Nano generates 5 volts through a voltage regulator which then connects via the “5V” pin to the other boards as shown.  The risk here is a mistake with 10V may burn out one or all of the boards (best get it working on 5V first).  Also note – the Nano’s voltage regulator isn’t designed to power other modules so run it on the lowest voltage possible to avoid overheating.

The 5V (vss) and gnd power connections are self-evident and connect to all boards.  Below are the other connections.

From	To
Nano D2	SD card reader CS (chip select)
Nano D3	GPS TX
Nano D4	GPS RX
Nano D11	SD card reader Mosi
Nano D12	SD card reader Miso
Nano D13	SD card reader Sck
Nano A4	BMP Sda
Nano A5	BMP Scl

The Nano has a reset button and pressing this when its running will close down the current data file, open a new one and reset altitude to zero.  This is useful just before a launch!   I used a nylon screw/nut through the case, left with some slack so pressing the screw head hits the button!

It can be first built on plug in bread board first just to get it working of course!

 

 

Software

Software version “gps_var_rate_serial.ino”    and     “gps_var_rate.ino”

I decided to have the software sample at 4 hz but write at a variable rate to the SD card. Every 1 second up to a speed of 75 mph, every 0.5 second up to 150 mph and every 0.25 seconds above 150 mph.  These thresholds values can of course be altered!   To overcome the issue of cheap modules “forgetting” their settings, the sample rate and GPS baud rate are programmed into the GPS module from the Arduino during each reboot.  This also saves having to pre-program them manually before use!

To accommodate the faster sample rate, the gps baud rate is set to (38400) and the serial data output is at 230400 baud.   This version will not work on a Fake Neo.6m (rebadged Techtotop TD1030 GPS).

 

 

Software version “gps_1s_serial.ino”    and     “gps_1s.ino”

This software uses a GPS that samples once per second and a gps baud rate of 9600 (the default settings). Suitable for a GPS module that cant be adjusted and is ok for slow to medium speed models.  The serial data output is at 115200 baud and should work on all Ublox GPS modules (and their fakes).

I have noticed that spirited aerobatics can temporarily affect GPS reception but this is usually only a few data points affected (the data freezes briefly!).

 

The software need various libraries installed into the Arduino IDE to work.

https://github.com/mikalhart/TinyGPSPlus/archive/refs/heads/master.zip

https://github.com/greiman/SdFat/archive/refs/heads/master.zip

https://github.com/adafruit/Adafruit_BMP280_Library/archive/refs/heads/master.zip

If you don’t know how to install library files, see https://support.arduino.cc/hc/en-us/articles/5145457742236-Add-libraries-to-Arduino-IDE  in particular the bit about importing .zip files.

 

Each version of the software has 2 options, one that reports the data as a serial stream as well as onto the SD card. The other version only stores data to the SD card.   The serial version shows the data live to the Arduino IDE’s “serial monitor”.  The non-serial versions have this disabled simply to give a bit more headroom for the software memory on the Arduino and is best for the version that will fly!

Using the Serial monitor

With the dataloggers Arduino attached to the PC via a USB lead and the Arduino IDE program running, press the serial logger (top right of the screen and looks like a magnifying glass with a dot in), check its connected to the correct COM port (Tools > port) and set the baud rate to 115200 or 230400 depending on software version. You should see the data appear line by line each second on the screen.  You can see its altitude vary if you lift it up a few feet.  If its gibberish you have the wrong baud rate!

 

 

[dave windymiller]

To view data, use Google Earth

Download & open Google Earth.

Remove the SD card and insert into an SD reader on your PC.  

In Google Earth, use  - File – Import – {select the file from the memory card reader Dataxx.csv}.   Ensure “Delimited” and “Comma” are ticked then press “Finish”.

It will ask , “Do you want to apply a style template to the features you ingested?”  Create a new template and you will get:-

 

In “Color” 

1)      Set “color from field”.

2)      Select “speed” as the field.

3)      Set the start colour to blue and the end colour to red.

4)      Change the number of “buckets” to a high number say 50 (this is the number of shades between blue and red!). 

Note - you cant have more buckets than you have number of different speeds in your data!

5)      Press “height” tab.

 

In “Height”

1)      Select “Set height from field”

2)      Select “Height” as the field.

3)      Select “Continuous”

4)      Slide the slider so the maximum height to be displayed is approximately the same as the maximum in the data for realistic height display on the map (you can make it bigger if you want to exaggerate the altitude display?).

5)      Select feet (the gps records hight in feet on the SD card).

6)      Press OK.

7)      Save the setup file as a name e.g. “height and speed.kst”

 

More to follow!!!

 

 

[PDB]

Thank you @dave windymiller, pleased you've gone ahead and documented this, I'll be making one, very much appreciated. 👍

[Peter Jenkins]

Great job Dave.

 

Others might also be interested in the Flight Coach system that has been developed for F3A aerobatics but can be used for any type of flying.  This website gives detailed information on setting up hardware and how to use the free plotter software to display your flight.  This project has had the benefit of working with the Arduino folk to produce an excellent post flight debrief facility.  

 

The plotter is designed to segregate each manoeuvre in the FAI schedule but you can use the plotter without recourse to this function or you can choose to call each of your manoeuvres one of the named manoeuvres.  There is a facility to extend or contract the path of each manoeuvre if you wish to look at each segment in detail.

 

There is plenty of information on the Flight Coach website on how to set up the hardware/firmware and how to configure the plotter.

[Peter Jenkins]

Just found this video by Juan Rombaut, a world Top 20 F3A pilot, talking about how he uses Flight Coach to help him practice and improve.  Link.

[FlyinFlynn]

Well done Dave, I mistakenly thought you were using a Quectel L80 and I see you do initialise the module!  

 

Did you link the sketch?... I didn't see it.

[dave windymiller]

Hi. Yes i will post the codes, just havent got that far yet!     

 

-------------------

The map wont display it until you tick the data file you imported in “Temporary Places” on the left hand panel (below).

 

You can now zoom in and see the height and speed data on the map. Move mouse with LH button pressed to pan about. Middle button / roller pressed to rotate the view (as if looking out of a plane window!).  RH button zooms in / out.

Below is test data from me driving.  You can click on any data point to see the info.  Colour is speed and line markers are the height.  The fastest speed is in red!  Slowest is blue.

 

 

You can open any new dataset and apply the .kst file to format it. 

Note – there is a bug in Google Earth that fails to show the height when recalling a style template .kst file.   Simple Fix - When you apply the style template .kst file that you previously saved, also tick the “edit selected template” box.   You don’t have to save it again but this tick makes the height display correctly for some reason!

 

If you want to change the “style template” settings either create a new .kst file or tick the “edit selected template” when you select an existing template (.kst file).  Make your changes to display the data with revised ‘style’ (you can choose to save it or not).

You can open more than one GPS file and select which one to view with a tick in the data (LH “Places” panel).

Google earth is not particularly easy to use but the above will get you started!

 

 

 

[dave windymiller]

“Max speed and altitude o meter”

Whilst talking to a fellow model aircraft flyer about GPS’s etc, his view was that he cant be bothered to faf about with computers and just wanted a max speed and altitude indicator “so I don’t have to put my phone inside my funjet”.  I figured this wouldn’t be hard as it is similar to my max altitude recorder (my first tinkering with Arduinos) and adding a GPS would get the speed data.  

This is the same circuit less the SD card reader and with an 0.91inch SSD1306 128 x 64 OLED module (address 0x3C) connected to the same connections as the BMP280.  Ive written the software based on a once per second GPS data rate. 

As with the full-blown logger, the software also has a “serial version”, which is more for interest/testing/setting up purposes with its typical output as shown below (sat on my bench going nowhere!).   Only a few satellites picked up so not full accuracy at this point!

 

 

After power up, the display shows Max speed 0mph and Max alt 0ft.  These values increase as the data does and is only updated if the values are higher until the reset is pressed.

 

Max speed and height circuit.

 

Library files for the display

https://github.com/adafruit/Adafruit_SSD1306/archive/refs/heads/master.zip

https://github.com/adafruit/Adafruit_Sensor/archive/refs/heads/master.zip

 

 

 

 

 

[dave windymiller]

Attached Sketches (or programs for us oldies)

gps_1s.ino gps_1s_serial.ino gps_var_rate.ino gps_var_rate--serial.ino

[dave windymiller]

altimeter.inoaltimeter-serial.ino

 

Max speed and altitude o meter files

Edited March 23 by dave windymiller

[FlyinFlynn]

Looks good Dave!  Thanks for posting.   I'm looking to utilise a smaller uP and GPS and have some bits on order. I have taken a look at porting your sketch over and I think it should be ok. I did start writing a sketch from scratch and this is as far as I got (without the hardware to test it all out). It does produce a nice serial output though!

GPS_Logger.ino

[Brian Dorricott 1]

Thanks everyone something to get me interested putting the E back into RCME . I copied completely a GPS/Arduino data logger with SD card from the internet and made a couple for lads at my club with just a few alterations to the code to display speed etc . The format of the output isn't right to display on Google but I will have a look at the code above and see if I can work it out . I've got an homemade Arduino Frsky GPS logger I got that to display in the Frsky suite the location and height data. The SD card version just displays location,height,speed and time which is all the CAA want for +25Kg models I think .

Nice to know someone else is tinkering and getting results .

[FlyinFlynn]

OK, Dave, I have made a couple of minor mods to your sketch and now have it working on the same hardware as the RiD I was playing with. It is currently working on a ESP32C3 super mini dev board and a ATGM337H GPS module but I intend to swap the gps module out for a HT1818Z3G5L module when new supplies arrive.  I am now working on designing a PCB for it.

 

busy busy busy

🤪

WindyMillersDataLogger.ino

[dave windymiller]

Hi FlyinFlynn

 

Looks good. Interested to hear how it goes with both gps'.  Ive ordered a ESP32C3 to play with and a smaller sd card too (i used what i had in "stock"!)! 

 

Point to note that the my original sketch was evolved to suit the barely adequate memory of the nano,  particularly with respect to the writing of strings of data. Making a single string with several appended variables pushed it over the edge with erratic results.  Your processor wont have that issue!

 

Re flight coach, i have looked for hardware requirements for it but yet to find any (the first link from Peter Jenkins doesnt work for me!)  Any info would be appreciated. 

 

cheers 

Edited March 25 by dave windymiller

[Peter Jenkins]

4 hours ago, dave windymiller said:

 

 

Re flight coach, i have looked for hardware requirements for it but yet to find any (the first link from Peter Jenkins doesnt work for me!)  Any info would be appreciated. 

 

cheers 

The Flight Coach website seems to have gone down as I cannot access it either.  You can find a short write up on it on the CK Aero website (link) and some information on boards here.  I will try and find out why the FC website is down and post the outcome on this thread.

[Peter Jenkins]

Comment from one of the Flight Coach team:

 

We are having some DNS issues in European. We're looking into it, could be something to do with some new EU rules. For now you can access it by setting a preferred DNS in your ipv4 settings. I just chose a random one in Australia (one from here: https://public-dns.info/nameserver/au.html) and that fixed it.

 

I did try the URL I posted and it now seems to work but for how long?  If you get to flightcoach.org, then you will see this home page:

 

 

The Software Manual and Hardware Setup tabs should give you the information you need.  It doesn't seem to specify any particular board though.

 

[FlyinFlynn]

PCB done, now just the long wait to discover where I messed up 🤪

 

I tried to panelise them because 4 would fit under the 100mmx100mm minimum price PCB  size but I'm not sure it worked!... 

 

I'll wait until a successful test before releasing the gerbers but I think the circuit is right if anyone wants to design their own PCB.

 

 

[Bob Burton]

17 hours ago, dave windymiller said:

Making a single string with several appended variables pushed it over the edge with erratic results

Do you mean Strings or strings ?

 

The former is notorious for causing problems in the small memory footprint of AVR processors, whereas the latter keeps the use of memory under control.  Having said that, more memory and a faster processor at a reasonable cost is a welcome upgrade

[FlyinFlynn]

It progress init!  The Arduino drawer in my parts box has gathered a good layer of dust. The latest offerings from the ESP32 family are faster, smaller, contain more Flash memory, more Sram, faster clock speed, have WiFi and bluetooth capability., etc ,etc...... the prices of the super mini and their ilk are dropping and are the same price of a nano or less (I've seen them well under $2 each), The only limiting feature would be the number of I/O pins but if you need more there is always the ESP32 dev boards. There is wide-ranging support for the Arduino IDE for programming if folks are still wedded to it.

 

What a great time to be an enthusiast!

[Brian Dorricott 1]

FlyinFlynn if you are UK based would you be interested in selling some pcb boards to offset your costs ? I'm a complete numpty when it comes getting circuit boards done , last lot I ordered ended in the bin.

[FlyinFlynn]

21 hours ago, Brian Dorricott 1 said:

FlyinFlynn if you are UK based would you be interested in selling some pcb boards to offset your costs ? I'm a complete numpty when it comes getting circuit boards done , last lot I ordered ended in the bin.

I'm in France but please don't hold that against me!.    I am not adverse to selling some on once I have built and tested one 🙂, especially if the  panelising works because with 6 boards to each panel and the minimum order of 5 boards I will have a few spare. It cost me ~$10 per batch but it kept me busy the whole day so I see that as a good price for a whole days entertainment - any price will be pretty much just postage.... if it happens!

 

I have also done a design using a Seeed Studio Xiao ESP32C3 instead of the super mini. I have a few of them and as the design doesn't employ wifi it doesn't need the external antenna those boards come with. I don't suppose anybody will really be interested though because the Xiao costs quite a bit more than the super mini .

 

Incidentally, there are two ESP32C3 'super minis', this is the one you want - 

 

This is a ESP32C3 Zero, sometimes conflated with a esp32c3 supermini, it has a RGB Led on board and has a different pinout -

 

 

Easy to confuse the two!

 

Here is the Xiao - It is very slightly smaller than the supermini if you ignore the external wifi antenna

 

 

 

Quite a few of my previous boards ended up in the bin too, it is amazing how little time you need with the PCB in your hand to spot the fubar you spent a whole day looking for before pressing the 'buy' button.

[Bob Burton]

1 hour ago, FlyinFlynn said:

it is amazing how little time you need with the PCB in your hand to spot the fubar you spent a whole day looking for

That sounds all too familiar