Wednesday, 12 December 2018

The Supair Delight 3

The Supair Delight 3 is a delightful harness - it really lives up to its name!

This post is loosely related to the Bluefly (in the video below you can see some Blueflys on the Delight 3 flight deck), but is more of a general review of paragliding gear and how it can complement each other.

During over 20 years of paragliding I have only ever purchased three harnesses for solo flying - the harness I got with my first wing, then about eight or ten years ago a Kortel Karmasutra II (I added a pod about six years ago), and now the Delight 3. In this post I hope to describe why I choose the Delight 3, and after flying it for a bit, what I think about it.

In a previous blog post I described flying my Nova Mentor 5. In that post you can read about what kind of pilot I am (classic weekend pilot, and more recently with the occasional comp), and what it is like flying around Canberra (technical, mix of mini xc and ridge soaring).

I purchased the Delight 3 from Mark at Cloudbase Paragliding. It is in his shop here. He was great to deal with and shipped it to me very quickly.

Why the Delight 3?

The decision to move away from my older Kortel Karmasutura II was motivated by its weight and bulk. It is a very comfortable harness in the air, but it is really too heavy to carry up a hill too many times. It is also pretty big, and only fits in my glider bag with a lot of squeezing during pack up. It is lovely in the air, but on launch I was annoyed that it got in the way of my helmet when looking up at the wing, and the pod knocked me in the back of the knees during take-off. I have been looking for the right harness to come along for a while.

There were a few features I was after in new harness - lightweight, pod, integrated flight deck, and good back protection. The Delight 3 had all of these. I trusted the excellent reviews by Flybubble and Ziad and decided to order one. Read those reviews as well as this to consider if this harness is for you.

First Impressions

I have the Delight 3 size M. When I first put my 180cm - 77 kg frame into it I thought I might be right near the top of the size - it was not too small, but it was a bit tight around the hips. However, I was doing the adjustments under a hang point on the ground, and the risers were not wide enough apart to simulate being under a wing. On the ground, I initially let most of the adjustments fully out.

Since then I have flown it a few times in very rough thermic conditions and very gentle smooth ridge soaring. Every flight I have adjusted everything a bit tighter and now feel that the size M is perfect for me. All of the adjustments have ended up at about the halfway point. Adjusting a harness to match your flying style can be a bit finicky, and this is especially the case for lightweight gear. Now I have tuned the adjustments, the Delight 3 is exceeding my expectations.

The video below shows the harness in the air during a very early morning ridge soar at Lake George. Please forgive my sloppy camera work and editing.



Comfort On The Ground

The harness fits nicely into the Nova glider bag with my wing, and I still have room for helmet and lots of other things. I have been really surprised the difference 4 kg makes. Sure, it is much better for hiking up a hill, but I also notice how different it is just putting the glider bag in the car and putting it away when I get home.

When strapping in ready for launch it feels much more comfortable than my old harness, although the attachment arrangements are very familiar. The integrated flight deck sits a little awkwardly prior to launch at first, but it really only took me one launch to get used to ground handling with it. Overall I can ground handle much easier, actually tilt my head to look at the wing, and the launch process feels a lot tighter.

Pleasant Flying

After launch I found it easy to get into the pod and into sitting position. I still need to adjust my pod straps a bit more to make them tighter, and this will help pull the flight deck closed a little more. The small seat board allows some weight shift control, and when I managed to work out the adjustments any tightness was gone. I like flying a little more upright than many pilots, and the semi rigid back supports that really well.

I like the extra feeling this harness provides compared to my old one. The Mentor 5 is a high end B wing, and the extra feedback through this harness allows me to squeeze a little more performance from a broken thermal. In the rougher conditions I was thrown about a little, but not too much and it actually gave me more confidence that I could fly the wing more actively.

The flight deck position is good, and as you can see in the video above is perfect for the Bluefly :)

Quality Features

This is a top quality harness with some great features.
  • Flight deck. The integrated flight deck is large enough for two main instruments, and one or two little ones. For comps I will end up flying with a Bluetooth model of the Bluefly that I will use for audio, an Android phone running xcosar, the Kobo Mini + TTL_GPS Bluefly, and a Spot. There is enough room behind the flight deck for a backup battery, radio, lunch, and other random things. I like the added extras such as the little loops and clips for attaching instruments, and the hole for a charging cable from the backup battery to the phone. 
  • Reserve. The reserve configuration appears smart and accessible. I am flying with a full size reserve, and was able to pack it so that it fits, but can still be test thrown without too much force. 
  • Pod. Nice things about the pod include the magnetic closure clips - they just seem to work. The way the speed bar is attached makes it easy to access - but is it still kept out of the way.
  • Internal pockets. The internal pockets on each side under the risers are really handy. One side has the tree attachment carabiner and cable (the one I used for the camera in my test flight), and the other is the same configuration internally but without the cable. I put my camera on a selfie stick in that side. 
  • Passive safety. I am familiar with the benefits of passive foam back and under seat protection. I am probably alive because of this kind of protection after a bad accident a few years ago. 
Overall Impressions

I am super happy with this purchase - it really is what I was after. The harness is a great match for my high end B wing, works well with my instruments, is comfortable on the ground and in the air, and has a bunch of features that I wanted. I am not sure that I could suggest any improvements to the Supair designers.





Friday, 7 December 2018

BlueFlyVario_TTL_GPS_v12 firmware update

Today I have released a firmware update for the BlueFlyVario_TTL_GPS_v12 (firmware version 12.219). This update changes the way data from the on board XA1110 GPS is cached by Bluefly processor and multiplexed with the normal Bluefly output. Updating the firmware on a Bluefly attached to a Kobo requires that it be removed, so this post also describes how you can use an xci file to adjust the GPS without having to update the firmware.

When the TTL_GPS_v12 model of the Bluefly was released the GPS module was upgraded. The new XA1110 GPS module communicates with the Bluefly processor over UART at 115200 baud. A few months ago some issues were found when using the Bluefly with LK8000 that we thought that were being caused by occasional errors in the communication. This knowledgeable article describes how to change the baud rate as a workaround.

However, additional testing discovered that in some circumstances (such as when tracking a lot of satellites), too much UART data was being sent from the XA1110 in a short time and the Bluefly could not keep up. This was causing errors in some re-transmitted GPS sentences, and some sentences were even being dropped. Location sentences are being transmitted successfully, which is why initial testing did not pick up the bug.

The firmware update described in this blog post allows the Bluefly processor to cache the GPS data in a more robust way. Many hours of testing suggests that all GPS sentences will now be transmitted without error.

Thanks to those Bluefly users who helped us workout the bug.

What models are affected?

The bug affects BlueFlyVario_TTL_GPS_v12 (with the XA1110 GPS/GLONASS module) shipped between initial release on 7 Jul 2018 to and 27 Nov 2018. Varios shipped from 28 Nov 2018 date have the updated firmware.

This firmware update does not apply to the Bluetooth_USB or USB models of the Bluefly.

If your vario is installed on a Kobo and you are running xcsoar you can see what version of the firmware you are running by starting (or restarting) the vario while you are looking at the Device monitor (Menu|Config|Devices|Monitor). See the image below which shows the firmware loaded on this device is version 12.218.


What should I do?

If you have firmware 12.2.18 there are a few options:

Option 1 - Do nothing. If you are happy with the performance of you vario, and it is installed on a Kobo on which you are running xcsoar, then you may wish to do nothing. This will be ok for some pilots, but if you are using your GPS tracks for competitions or want increased confidence in the performance of the GPS then I recommend option 2 or 3.

Option 2 - Change the baud rate. Changing the baud rate between the Bluefly processor and the onboad XA1110 is a workaround which provides a reliable fix. If your Bluefly is soldered to your Kobo, and you are running xcsoar, then this is probably the easiest thing to do. You can change the baud rate in two ways:
  • Use the baud rate update procedure described in the knowledgebase article.
  • Use the BlueFlyDebug_28Nov18.xci file to send the same commands to the Bluefly to change the baud rate, but without  having to disconnect it from the kobo. See Nev's extensive information on xci files here for more information on how they work. To to this:
    1. First download the xci file to your pc, then get it onto the Kobo in the xcsoardata directory. 
    2. Load this xci file to create the BlueFly menu using Menu|Config|System|Language,Input|Events
    3. Restart to apply changes. 
    4. Look at the monitor (Menu|Config|Devices|Monitor) to make sure the BlueFly is running by seeing the data is streaming in. The GPS sentences are the ones starting with $G
    5. Check that your new BlueFly menu is working and that you have two way communications with the Bluefly. (Menu|BlueFly|SimulateButton). You should hear a beep as if you were pressing the button on the Bluefly. If you don't hear anything from the Bluefly then there is probably a problem with physical connection and you will need to fix that before continuing. 
    6. Go into the GPS Adjustments menu (Menu|BlueFly|GPS Adjustments). 
    7. Press Menu|BlueFly|GPS Adjustments|GPS Command Mode. That sends the command PGCMD,380,7 which puts the XA1110 GPS into command mode. Note that xcsoar adds the appropriate checksum and end of line information to the command. 
    8. Press Menu|BlueFly|GPS Adjustments|XA1110 9600 Baud. That sends the command PGCMD,231,1 which adjusts the XA1110. 
    9. Fully shutdown and restart the Kobo. This ensures that the Bluefly, and its attached XA1110 GPS, are fully powered down and restarted. The baud rate changes to the GPS do not take effect until you have done this restart. 
    10. Have a look at the device monitor again. Now you should not see any GPS sentences. We have adjusted the data rate from the XA1110, but now we need to adjust the rate of UART 1 on the Bluefly process so it picks up those sentences. If you do actually see GPS sentences before you have adjusted U1 then you might not have successfully done step 6, 7 and 8. 
    11. Change the Bluefly U1 baud rate by pressing Menu|BlueFly|GPS Adjustments|U1 Baud 9600. 
    12. Look at the monitor for the last time and you should now see GPS sentences again. The GPS Tx baud rate is 9600, the Bluefly U1 Rx baud rate is 9600, and if you have the defaults the Bluefly U2 Tx baud rate is 115200, which allows it to keep up with the GPS information. 
    13. Note that I have also included buttons for adjusting U1 back to 115200, and also for adjusting the XA1110 baud back to 115200.
Once you have done that, you are still running the older firmware, but the U1 baud rate means that the Bluefly processor with that older firmware can keep up with the GPS data sending rate without errors. 

Option 3 - Actually update the firmware. To update the firmware you will need a USB serial adapter, the Bluefly must be removed from the Kobo, and you will need the ds30 loader from the firmware page. Removing a Bluefly from a Kobo can be tricky, and if you are not very practiced with good soldering techniques then it is likely you will damage the Bluefly, the Kobo, or both.

The firmware update procedure is the same as for the v11 as described here: http://blueflyvario.blogspot.com/2016/08/firmware-update-for-v11-models.html.
Alternately, you can ship the TTL_GPS back to me and I will update the firmware for you. If you want to do that please contact me and I will send you the address and instructions.

Saturday, 7 July 2018

BlueFlyVario_TTL_GPS_v12 released

In April 2016 the v11 model of the BlueFly TTL_GPS was released. That model is now in use by many thousands of pilots around the world. Most pilots install the TTL_GPS model in a Kobo and run xcsoar. Today I am pleased to release a major update, the BlueFlyVario_TTL_GPS_v12.

Why a new model?

This update was driven by the reduced availability of the PA6H GPS used on the v11 (and all earlier BlueFly TTL_GPS models). Just over a year ago Sierra Wireless purchased GlobalTop, the manufacturer of the PA6H. For some time the PA6H module was available, but over the last few months all of my suppliers have run out of stock; I had to choose a new GPS.

I have selected the SierraWireless XA1110. From their website:

'AirPrime® XA1110 Multi-GNSS Module with Patch Antenna

Compact, high-precision, ultrafast TTFF Multi-GNSS positioning with integrated antenna. The XA1110 supports tracking of GPS+Glonass or GPS+Glonass+Galileo satellite system combinations to deliver superior positioning accuracy of <2.5m (with SBAS). Based on MediaTek's latest MT3333 engine, it’s the smallest integrated antenna multi-GNSS module on the market with an ultra-compact form factor of 12.5 x 12.5 x 6.8 mm.'


In practice, I feel that there is a significant performance improvement over the PA6H, and some better features:
  • GPS + Glonass means quicker fixes and better tracking in many parts of the world. 
  • The smaller size fits better on the board, and allows for a better ground plane layout on the PCB. However, note that the patch antenna is about 1.5mm higher than the PA6H. 
  • For advanced users, there is good documentation on the Sierra Wireless website on sending commands to GPS module to customize its performance (in our case via the BlueFly). 
  • The XA1110 default baud rate is 115200 (this has resulted in some changes outlined below). 
What is in the bag?

The v12 is supplied with the same parts as the v11:
  • The main module. The PCB size is 50mm x 17 mm which is the same as the v11. The speaker, GPS, button and header locations are in the same spot as the v11. 
  • A small piece of neoprene. This is really important. It must be placed over the pressure sensor if the sensor is exposed to any light (even light through a translucent case). The neoprene allows the air pressure through, but stops the light. Light makes the pressure sensor go crazy. It is really important to place it on the pressure sensor with the black foam side down - do not stick it to the pressure sensor - you will block the hole and it will not work!
  • Some blue PVC heat shrink cut to size. 
    • Put the neoprene on the pressure sensor, and the heatshrink evenly over the module.
    • Use a heat gun, or a hairdryer on hot setting to carefully shrink the plastic around the module.

Hardware changes

There have been a few hardware changes from the v11.
  • Much of the layout is identical, but the components around the GPS have been moved around for better positioning. 
  • The behavior of the blue LED which provides a GPS indication is now different. It is not lit to start with, and then flashes at one pulse per second when the GPS get a fix.
  • There are a few pads on the back side of the board for users who want to experiment, but I recommend leaving them alone as unless you really know what you are doing:
    • SJ1 is still used to bypass the button function for turning on the module as soon as power is supplied to Vin. I still do not recommend closing this for most installs. If you are considering using it then also consider using the new startDelayMS hardware setting. 
    • There are pads to connect a super small backup battery to the GPS VBACKUP. I feel that this is not needed for most installs, and it actually causes more problems than it solves. The pads are designed for a XH414H-IV01E battery which is currently widely available from ebay and aliexpress.  
    • There are pads for an external antenna header for the XA1110. Before you consider using this you should read the XA1110 documentation in detail so you know what kind of antenna to use. The pads are designed for a U.FL-R-SMT IPEX connector. I have not yet experimented with it very much. 


Firmware Changes

New features of the v12 firmware include:
  • There is a new hardware setting called startDelayMS
    • This adds a startup delay before data is sent to the Kobo. Some models of Kobo do not react well if data is received during the Kobo boot process. If you have closed SJ1, then you might need to adjust this setting to achieve a stable startup. 
    • You can adjust the duration of the delay by sending the command $BDM DELAY*, where DELAY is the delay in milliseconds.
    • If startDelayMS is set to anything other than zero then you will hear two very short high pitched beeps as soon as the vario is started, then the delay happens, then the normal vario start up procedure kicks in and data starts flowing from the BlueFly.  
    • The default setting is 0. 
  • Some default values for hardware settings have changed:
    • uart2BRG (BR2) = 16. The default baud rate between the BlueFly and the Kobo is now 115200, which is now the same for all of the Kobo models. 
    • uart1BRG (BRG) = 16. This sets the baud rate between the BlueFly processor and the onboad GPS to 115200. 
    • heightSeconds (BHT) = 3600. This changes the default auto power off from 600 seconds (10 minutes) to 3600 seconds (1 hour).
    • toggleThreshold (BTT) = 2000. This changes the auto toggle back on feature to react to 20 m/s lift or sink, instead of 1 m/s lift of sink. Most pilots prefer to just use the button to turn the sound on and off. 
  • The maximum value for all hardware settings is now 65534 (0xFFFE), although I am yet to update the BFV Desktop app. 
  • Some pitot related code has been updated for those advanced tinkerers who are experimenting with an airspeed sensor. 
Installation

See this previous post for an example of how to install the vario on the Kobo Glo HD. There are many links on that post that describe a few different ways to install the vario.

Also, see Nev's page for many examples of which serial port to use on different models, and for a great explanation of how to create a custom xci file.

I still feel the simple install is best. The image below shows a simple installation on the Kobo Glo HD. I normally just attach the vario to the bevel which is closest to the internal serial port. I use double sided tape to hold it in place, then encase the wires and secure around the edges with hotmelt glue. In this install the xcsoar settings have been changed to landscape orientation.

Some tips which are applicable to all installs:

  • Use the neoprene, but do not use the sticky side which would block the holes in the pressure sensor.
  • Make sure you connect the BlueFly-Tx to the Kobo-Rx, and the Kobo-Tx to the BlueFly-Rx. 
  • Set the baud rate in xcsoar to 115200. 
  • Read an earlier blog post about using xci files. That is currently the easiest way to send commands to the vario (you also need to read the hardware settings manual on the support page of the website).
  • Check your wires to ensure the solder quality is good, and that the wires are not routed next to other components on the Kobo circuit board which might pick up stray power. I like to keep the wire length less than 5cm.
  • If you get 'Waiting for GPS fix' shown in xcsoar, and after 10 minutes of the vario being on, outside, and with the antenna having a clear view of the sky, the do the following debugging:
    • Check in the Devices Monitor for incoming data from the vario.
    • Record a NMEA log and look for messages from the GPS to assess what is going on with the satellites.

Thursday, 2 November 2017

Airspeed Sensor Updates

Almost two years ago I blogged about an airspeed sensor shield for the BlueFly. This blog post is about a new approach to integrating an airspeed sensor with the BlueFly. It is still far from perfect, and still requires experimentation, but is a bit more accessible for those who want to tinker.

The Sensor

Instead of producing a dedicated sensor I am relying on the widely available MS4525DO based sensor which is used by the R/C community. This uses the same differential pressure sensor as the dedicated airspeed sensor I used to produce for the BlueFly. However, because of the volume of manufacturing they can be produced at a cheaper price. Search ebay, aliexpress, banggood, hobbyking, or your favorite supplier of electronics from China for 'px4 airspeed'. You should get many results. Make sure to select one of the sensors based on the digital MS4525DO (white) instead of the older analog sensor (black). You can read more about this sensor on the pixhawk website


The Enclosure

A 3d printable enclosure is designed to hold the sensor and BlueFlyVario_Bluetooth_USB_v12 (or the USB only version). It is far from a perfect design, but even on a rough 3D printer (like mine) is useful enough. You can grab the design from thingverse. Note that the lid and main part of the case are designed to be glued or held together with tape. Below is a photo of the BlueFly with airspeed sensor installed in the 3D printed case. 


Firmware Update

Before going on please update your firmware to the BlueFlyVario_12.M16 version. The firmware changes include:
  • Fixed a bug with MS5611 temperature sensor output (that is only relevant for tinkering)
  • Changed outputMode 6 (BFV Extended Sentence) to include the MS4525DO sensor temperature. The sentence is now in the following format: $BFX,pressure(Pa),vario(cm/s), MS5611temp(deg C in 2 decimal places), battery(%),pitotDiffPressure(pa), volts(V), pitotTemp(deg C in 1 decimal place)*checksum\r\n 
  • Ensured that if you send the command $BUP 1* that it always triggers an differential pressure sensor calibration sequence (which takes about 10 seconds). 
Assembly

The first step is working out what to connect to what. The sensor is connected to the I2C port of the BlueFly. You will need to ensure:
  • BlueFly-Gnd is connected to PX4Airspeed-Gnd
  • BlueFly-SDA is connected to PX4Airspeed-SDA
  • BlueFly-SCL is connected to PX4Airspeed-SCL
  • BlueFly-V+ is connected to PX4Airspeed-+5V. Note that the the BlueFly actually only provides 3.3V, but my experiments suggest that there is no degradation in performance of the MS4525DO sensor at this voltage. 


After soldering, the connections are shown below. You will need to cut and solder the wires to the length required for your enclosure. 


The image below shows the connected sensor and pitot tube mounted in the 3d printed enclosure. Note:
  • The BlueFly mainboard mounts in a similar way as in the standard sky blue case. 
  • The upper nozzle on the differential pressure sensor connects to the pitot part of the pitot tube, the lower nozzle on the static port. 
  • You should use a few dabs of hot melt glue to keep the pitot tube and px4 airpeed sensor firmly in place. 

Configuration

At the time of writing this blog post the only app which I am aware can read the indicated airspeed is xcsoar, and only when using the BlueFly in outputMode=2 (LX mode) and xcsoar configured to use the LXNAV driver. Key points:
  • You first configure the BlueFly to outputMode=2 and usePitot = true using the BFVDesktop app or by using direct serial commands. See the hardware settings manual for information about how to adjust the settings.
  • In xcsoar, set the driver to LXNAV and connect to the appropriate port (Bluetooth or over IP as appropriate for your model of BlueFly). 
  • In xcsoar, you should now see the Airspeed IAS info box provide the indicated airspeed reading. Note that this is different from the true airspeed. At low speeds (less than about 10km/hr) it will jump around quite a bit. At our paragliding and hanggliding airspeeds it should be accurate to about 1km/hr or less. 
  • Note that you can send the command $BUP 1* (this is the same as usePitot=true) to trigger a zero calibration of the differential airspeed sensor. A zero calibration will always be triggered on startup, and should be re-triggered only when the actual airspeed of the pitot is zero. 
If you really want to tinker and develop a custom app which uses the full features of the airpeed sensor then you will probably want to read the sentence from outputMode=6 ($BFX,pressure(Pa),vario(cm/s), MS5611temp(deg C in 2 decimal places), battery(%),pitotDiffPressure(pa), volts(V), pitotTemp(deg C in 1 decimal place)*checksum\r\n ) This provides the MS5611 pressure and temp, and the MS4525DO pitot differential pressure and temp. With some smart coding you should be able to calculate the true airspeed, and even develop a total energy calculation.

On the hardware side, you might want to add a push button for zero calibration. The firmware polls RB10. An internal pull up keeps it high, but if you use a push button to ground then zero calibration will be triggered. 


Todo

As always, there is more to do; manual updates, testing, more software, better physical layout for mounting in a paraglider or hangglider, etc. 

Sunday, 15 October 2017

Flying the Nova Mentor 5 in Canberra

A few months ago I starting flying a new Nova Mentor 5. It is so lovely that I decided to write a few words about it. Read on to hear about it's precision, stability, and performance.

This blog post is only loosely related to the BlueFly. One of the common queries I get from BlueFly users around the world is what wing I fly, and sometimes what the flying is like around Canberra. I will answer both of those questions in this post. 

What kind of pilot am I? In between a full time job, making and shipping well over 100 BlueFly's each month, and doing family stuff, I get time to fly. I have been flying paragliders since 1995 and am probably best characterized as a classic weekend pilot. Most of the time I stay pretty close to launch; dancing with light thermals below airspace, or making optimum use of a little ridge lift. I also fly tandem with family and friends (not commercially). 

What is Canberra flying like? Our sites around Canberra are not suited to big XC. The flying here is very technical if we want to make use of limited lift to do some little XC. We have a great club, and you can read more about flying Canberra at www.acthpa.org

Launching at Collector near Canberra - I actually ended up catching a few thermals after a sinking launch. 

Why an EN B wing? With over 20 years flying paragliders I have flown all kinds of wings. If you have been reading this blog since the beginning you may recall that I had a bad accident when flying an EN C wing. In fact, it was recovering from that accident which gave me the time to mature the BlueFly from a few prototypes to begin shipping them around the world. After that accident, I got a Nova Mentor 3 (M) and have enjoyed every flight on it.

I don't get enough spare time to travel to many far away places, or any time to fly during the week. Around Canberra we are often low to the ground and the air can be quite rowdy. A comfortable EN B wing strikes the balance between performance and stability for someone like me who might go a month without flying, and then not get many consecutive days. 

Why the Nova Mentor 5? I loved my Mentor 3 (M), but after loosing a few kg I was near the bottom of the weight range and decided to get a smaller wing. The Mentor 5 (S) had just been released so I made a quick decision to get one. I have always appreciated Nova's premium quality and support (Nova are not contributing to this by the way; I am just a happy customer). 

Shaun (in front), and me (at the back) kiting in a very light breeze
I have now flown the wing in a lot of winter thermals, and as Spring has begun in Canberra, in a few sharper thermals that throw me around. I have nothing bad to say about the Mentor 5, and love the precision, stability, and performance. 

Precision: This surprised me. Part of the reason the Mentor 5 (S) does exactly what I ask of it is because my wing loading is greater (top third of the weight range), but it is much more than that. I can hold a tighter turn and keep the wing just where I want it. When encountering turbulence I do not get thrown out of lift. I feel like the precision is at least as good as my EN C wing of four years ago.

Stability: The wing seems to stay solidly above my head, with only minor inputs required to keep it there. Even in some rough air I have only had a few little tip tucks, and they have popped out very quickly. The wing easily enters and exits big ears, and the longish brake travel seems like an inadvertent stall is very unlikely. I have not done SIV on this wing yet, but already I have more confidence than my Mentor 3. I am using speed bar much more!

Performance. Near the top of the weight range the sink rate is less than many other wings (when comparing using my 'am I at the top' test with a bunch of other pilots on a ridge). The wing is fast; at trim other pilots comment on the sound of the lines whistling though the air. On speed bar I have found I can already reach a few spots much more easily that my older wings. 

In summary, for a weekend pilot like me, the Nova Mentor 5 is a great choice. 

Well done Nova - another very pleasant wing. 



Sunday, 27 August 2017

BlueFlyVario_USB_V12 released

A busy work and family life means that I have only so much time for this hobby, and that time is almost entirely consumed by keeping up with orders for BlueFly varios; there has not been much time for development. However, today I can announce the release of the BlueFlyVario_USB_v12. This replaces the BlueFlyVario_USB_v11 and the BlueFlyVario_USB_GPS_v11.

The USB only model of the Bluefly is much less popular than the Bluetooth_USB model, (which is what you probably want if you are going to use it with a phone), or the TTL_GPS model (which is probably what you want if you are going to use it with a Kobo). Nonetheless, there are some reasons why the USB only model might be right for you:
  • If all you want are the great sounds of the BlueFly; then you can use it as a stand alone vario that beeps. 
  • If you are sure that you want to connect via USB to a PC, or to Android phone via USB OTG; then you can use it with xcsoar or another app. 
What is in the bag?

The BlueFlyVario_USB_v12 is essentially the same as the most recent revision of the BlueFlyVario_Bluetooth_USB_v12, but without the RN4678 Bluetooth module and some associated components. It has a slightly different firmware as the analog switch is no longer required to switch between the Bluetooth and USB output. See the image below for what is included:
  • The BlueFlyVario_USB_v12 mainboard. There is a small piece of neoprene covering the pressure sensor; glued at one end to hold it in place. 
  • The sky blue enclosed case. 
  • A 750 mAh singe cell Lithium Polymer battery. 
  • 4 x 5 mm M3 black nylon hex standoffs and 4 x 5 mm M3 black nylon screws.

Assembly

Follow the assembly instructions for the BlueFlyVario_Bluetooth_USB_v12.

Configuration

The BlueFly varios have many hardware settings to adjust the audio and lift/sink thresholds for beeping. See the hardware settings manual for a full description of all of the settings. Most people will just use the default settings. However, read on if you want to mess with them.

For most users the easiest way to connect will be to use the BFVDesktop application from a PC (available on the support page of the website). The v12 models of the BlueFly include a FTDI USB to serial computer. When you plug it in to your PC a virtual serial port will be installed. In the BFVDesktop application select the installed port, make sure the baud rate is 115200, then press connect. Test connection with the BlueFly by sending the $BTN* command, which simulates a button press on the actual BlueFly.

You could also configure the BlueFly from a suitable terminal application on the PC or Android by using the raw commands as described in the hardware settings manual.

Adding a GPS

I have discontinued the USB_GPS model at this stage. However, with a little basic soldering you can still add a GPS to the U1 headers. This can be done on the Bluetooth_USB model as well, but the GPS used in this example will not fit in the sky blue case with the bluetooth module and you would need to work out a way to suitably attach it to the outside.

The first step is to select a GPS which runs on 3.3v, has an included antenna, and has a TTL serial output. By default the U1 port on the BlueFly is configured to receive NMEA sentences at 9600 baud multiplex them with the normal BlueFly output, delivering the resultant data stream via the USB_Serial port at 115200. Any sentence arriving to the BlueFly at U1 which less than 82 characters long, beginning with $ and ending with *, will be gobbled up by the BlueFly and sent through.

A suitable GPS, and the one used in this example, is a widely available model used for RC flying. Search for "naze32 mini gps" on ebay, aliexpress, banggood, or where ever you get your electronic components. It is based on the ublox7 module, and I have found it to get a lock quickly and reliably. Also, it is just the right size to fit neatly in the sky blue case. Like most GPS', it defaults to a TTL output at 9600 baud which means it will work with the BlueFly without further configuration.

First, take the GPS out of its case and strip the wires. In the image below Red is 3.3v in, Black is GND, Orange is GPS-Tx (which will be connected to BlueFly-Rx), and Blue is GPS-Rx (which will be connected to BlueFly-Tx). Note that the wire colors might be different for you.


Next connect it to your BlueFly. Make sure your solder joints are clean and well made. Put a piece of tape on the BlueFly where the bluetooth module would have been to ensure there are no shorts between the underside of the GPS and the BlueFly board.


Finally, stick it to the top of the tape with more double sided tape and fold the wires away neatly. As the GPS module is just the right height you will not need the 5mm black stand offs at the GPS end of the board. It will fit neatly in the sky blue case, but make sure to be careful not to damage the button or USB connector as you put it in - do not force anything.


If you connect to the BFVDesktop app you should now see GPS sentences streaming in among the standard output from the BlueFly.

Note that it is possible for advanced users to further configure the GPS. The uBlox software to control a GPS is u-centre. It is possible to disconnect from the BFVDesktop app, and connect to u-centre. You will actually be connecting to the BlueFly at 115200 baud, even though the GPS is at 9600 baud. Some settings are available as the BlueFly sends any nmea sentence it receives from USB-Serial to the GPS as well. However, for any GPS setting feature which relies on binary communication, such as GPS firmware upgrades, then the multiplex magic of the BlueFly will not work.

Connecting to Android

Some users will want to connect the USB model of the BlueFly to their Android phone for use with xcsoar. If you have installed a GPS this might be what you could do with an Android device that does not have Bluetooth or a GPS. However, a disclaimer - I feel that that USB connectors are not designed for movement, and over time will be fragile if used on a paragliding flight deck, so I always recommend using the Bluetooth version if you have a choice. 

You will need a USB-OTG cable. The connection method is shown in the image below.


In the above image the BlueFly is connected to the UartBridge app. You can get it on Google Play here: https://play.google.com/store/apps/details?id=com.manichord.uartbridge. This app was designed to be used with the FTDI converter used on the BlueFly. It is open source and you can find it on GitHub. Thanks to Maks for the great work.

The UartBridge app will take the data coming in via USB-Serial at 115200 baud, and create TCP server on the local host to send it out on port 4353. In xcsoar you configure a device as shown below:
 

The BlueFly data (and multiplexed GPS data) will stream into xcsoar.

What about the TTL_GPS model?

At this stage I am not planning on a TTL_GPS_v12 model. The v12 Bluetooth_USB and USB models were motivated by wanting to fit in the larger 750 mAh battery, and incorporating the FTDI USB converter, neither of which applies to the TTL_GPS model. I am sure there will be mode development in the future, but I do not have anything in planning to replace the TTL_GPS at this stage.

Friday, 17 February 2017

Pressure Sensor Anatomy

At the core of over five thousand BlueFly devices is the MS5611 pressure sensor. One of the first blog posts about the BlueFly, almost six years ago, described the theoretical performance of this sensor, then about a year after that I posted about the success in testing. Back in 2011 there was not too much information about the MS5611 on the internet; only the manufacturer data sheet. Now the MS5611 is used in most of the varios which are similar to the BlueFly, and is widely used in hobby RC flying.

In this post I get technical about how the sensor works, and some of the things worth knowing about as you take care of your vario. This comes from having personally tested thousands of BlueFlys. I try to demystify how these sensors work in an accessible way, although I know it will still be pretty technical for many pilots. I focus on light sensitivity and some failure modes.

The MS5611

The image below shows the MS5611[01BA03] pressure sensor assembled on a BlueFly device. The sensor is 3 x 6 mm and is constructed of a small metal cap on top of a green circuit board. Solder pads underneath the sensor are used to connect it to the underlying BlueFly PCB, and provide power and the data interface. The BlueFly devices connect to the sensor using its SPI interface (instead of I2C) as it provides the best performance. To further improve performance the BlueFly provides power via a PI filter.

The image below shows the inside of the sensor with the metal cap removed. Inside the sensor there are two main components: a pizeoresistive absolute pressure sensing element, and a high resolution Analog to Digital Converter (ADC). It is reasonably easy to relate the functional block diagram from the datasheet to the physical layout inside.



The pizeoresistive element on the left is the MS7101. There is not too much information about it online, but you can see a few specs in this brochure. It is 1.25 x 1.25 mm, and to the naked eye looks like a grain of black sand. Infinitesimally small movements in the top of this sensor is part of where the magic happens for us. The top of the sensor is a very thin membrane of silicon with resistors etched on the surface in a particular pattern. This is like the skin of a drum on top of a hollow cavity. The silicon membrane is pushed in when you drop 10cm in altitude and about 20 trillion more molecules rush inside the metal cap of the sensor; this causes the surface resistors to change slightly. The resistors are part of a circuit which alters a voltage by a tiny bit, and the job of measuring pressure is half done. What is important for us is that it is super sensitive and repeatable as the silicon membrane flexes in and out. However, there are other things which can affect the resistance etched into the silicon other than flexing caused by pressure changes.

You can read more about piezoresistive sensing elements at the following links:
http://folk.uio.no/livfur/FYS4230/piezolecture.pdf
https://www.comsol.com/paper/download/182789/meenatchisundaram_presentation.pdf
http://pdfserv.maximintegrated.com/en/an/AN871.pdf

On the right is the ADC. Its main job is to turn the voltage from the pizeoresistive element to a digital signal. The component is more than just a standard super sensitive ADC, it also includes temperature compensation, some memory to store calibration coefficients, a digital filter, and sufficient digital circuity to allow communication the micro controller of the BlueFly. The temperature compensation removes most of the temperature induced inconstancy from the etched surface resistors in the sensing element, while the calibration coefficients allow for manufacturing inconsistency to be removed. Together these can present a super accurate digital signal. The magic of the MS5611 is that the ADC is very accurate and is designed to work at high clock speeds. This allows the BlueFly to get pressure measurements 50 times per second at 10 cm resolution, and with further processing in the BlueFly this means we can detect altitude changes very quickly.

Physical Vulnerability

The image below is taken from a slightly different angle. Here you can more easily see the vulnerability of the sensor. The holes in the cap, although tiny, are large enough for dust, grit, water, solvents, and even brush bristles, to get in. The most obvious vulnerability are the fine gold wire bonding connections. If any one of these wire connections is damaged then the sensor will not function correctly, even though it may still report a digital signal.

In addition, each of the sensor sub-components is coated in a clear sticky gel like substance; I guess for corrosion protection and perhaps some other stabilizing effect. This gel does not dissolve in water, acetone, or isopropyl alcohol, but it does seem to attract bits of dust and grit, which I think can affect either component in some circumstances.


Light Sensitivity

I spent a bit of time trying to understand the causes of light sensitivity. The video below shows the light sensitivity effect up close based on illumination from the LED's on my microscope. I think that at this range they provide the same order of magnitude light intensity as sunlight. The video pretty clearly shows that light sensitivity is due to the piezoresistive element. With a little internet research I found some theoretical descriptions of why this is the case. However, for our purposes the key is to know that protecting the sensor from light is vital to ensuring it works properly.


Sensor Protection

You need to protect your pressure sensor if you want your vario to perform well, but it also needs to be exposed to the air. The three strategies for protection are:
  • Put the whole vario in a case, although note that the translucent sky blue case used for the BlueFly does not block the light enough. 
  • Use the neoprene. I have spent some time testing different types of foam to find one which is effective at blocking the light, but permeable enough to air. The soft squishy side should be on the sensor, not the sticky side, which would block the holes. Every vario I send out has neoprene attached to the PCB in the right place, or in the kit if you are going to assemble it yourself.
  • Use a folded piece of black electrical tape, making sure that the sticky part of the tape is folded over on top of the sensor. This is a quick hack that can be done if you have lost your neoprene.
See the image below for a few examples.