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Jan 03, 2017, 03:46 AM
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FrSky S.Port sensor for ECU, Powerbox and link quality

I have put my code in Github to share:

Very rough version with little instructions for now. There are currently 2 sensors:
- ECU: Supporting Jetronic VX and Xicoy Fadec with EGT / RPM and 2-way telemetry for acting like an ECU terminal.
- Powerbox: Supporting batt voltage and GPS speed / height for now.
- LinkQuality: Reports the actual link quality in %. This is NOT the RSSI but actual quality of the received signal.

Powerbox will be updated with battery usage after i test with another powerbox that supports it. ECU will be updated later for more functionality and more types.

The best thing is you only need an Arduino mini (and a diode for 2 way ECU) to get it to work. Very cheap and small.

Building instructions added
Last edited by Tadango; Mar 03, 2017 at 02:33 AM.
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Jan 05, 2017, 07:04 PM
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vonkross's Avatar
Seems quite interesting.
Will you please elaborate a little more on the link quality sw/telemetry .
Jan 05, 2017, 10:10 PM
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Interesting, thanks for the code.

So the LinkQuality is an actual physical sensor, using an arduino mini, who is checking the data from SBUS and sending back that info as a sensor in the telemetry data?

Is it not possible to get the frame loss count in the radio in any other form?
Jan 06, 2017, 02:37 AM
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Correct. Frame loss count is done with an external device monitoring the S.Bus stream for the frame lost flag. This is the only way i can think of with the current firmware in the receivers. FrSky could easily add this to the existing firmware but until then a simple Arduino mini will do just fine. You only need a transistor and 2 resistors to create an inverter for the S.Bus. I will work on another solution (S.Bus compatible software serial) for that later.

You can also use 2 sensors for monitoring 2 receivers when using a RX8R or Redundancy bus / powerbox since you don't get an RSSI from the second receiver. Another usage could be testing a new or suspected faulty receiver by letting it fly along with another plane and monitoring the link quality. You can also create multiple sensors and test multiple receivers (different types / antenna's) at the same time when experimenting... the possibilities are endless

Btw, more detailed build instructions will be added later when i have my new batch of cheap Pro mini's and i have some more time....
Jan 07, 2017, 01:06 PM
Carbo (-nator) ;-)
Nice sketch, thx. I can confirm it works fine, very fast update frequency (10Hz?). Unfortunately the weather here in very uncomfortable now for flying. Here is an indoor test in rangetest mode. It is the first time, that i see a working link below 25 dB RSSI, usually it is a total breakdown - i will investigate this further (OpenTX 2.2 RC8).
Last edited by Allerhopp; Jan 07, 2017 at 01:22 PM. Reason: typo
Jan 07, 2017, 01:48 PM
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I see the same, below 40db rssi the link quality drops fast. I think a link alarm below 75% (for 1 second or more?) is a good warning for something wrong.

Low RSSI values in range test mode are normal. Only the TX power is reduced and the RX is still transmitting at full power so telemetry range is much more than the uplink.

The refresh rate depends on the amount of sensors also. I now send a value every fifth request.
Jan 08, 2017, 09:25 AM
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I logged the link sensor during 2 flights and the results showed a good link during both flights. The second flight had a strange interference (there was a UHF transmitter close the RX at that time) for a brief moment. Both flights were with a maximum distance of about 500 - 600 meters so nothing special. It was a 1300W electric jet trainer with 1300mm span.

A warning for a link below 80 or 85 for more then 0.5s should be a good option.
Last edited by Tadango; Jan 08, 2017 at 04:02 PM.
Jan 12, 2017, 01:02 PM
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This is very interesting. Are you planning to sell the sensor/ interface? I have Xicoy and Jetronic and since switching from Jeti I miss the EGT and RPM telemetry from the Xicoy Module. Really just looking for a way to detect a flame out as soon as possible.
Jan 12, 2017, 01:07 PM
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I am working on build instructions right now. Selling them would be difficult because of high shipping costs (probably). If you know someone who can build them for you that would be very cheap.
Jan 12, 2017, 01:36 PM
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Great, looking forward to the instructions. Thanks
Jan 12, 2017, 02:42 PM
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I added the building instructions
Jan 12, 2017, 03:06 PM
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Sweet, thanks
Jan 12, 2017, 03:23 PM
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lordsirob's Avatar
Thank you very much!
Jan 16, 2017, 02:31 AM
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Last weekend i (almost) completed the Powerbox sensor. It support all values now except for the GPS position, that needs some work.

The following values / sensors are available:
  • Battery voltage. Voltage is with 0.1 precision for sensors RB1V and RB2V
  • Battery capacity left (when the powerbox supports it). This shows the mAh left as RB1C and RB2C
  • Receiver errors: 2 custom sensors with ID 0x5130 and 0x5140
  • Framelosses: Custom sensor with ID 0x5150
  • Holds: Custom sensor with ID 0x5160

When a GPS is attached to the powerbox the following sensors are availalble:
  • GSpd: GPS 3D speed
  • GAlt: GPS height
  • Distance to home: Custom sensor with id 0x5110 that shows the distance in meters
  • Distance traveled: Custom sensor with ID 0x5120 that shows the distance traveled in meters (100m precision)

When a sensor is not availalble is it not tranismitted and cannot be discovered.

LED now shows the connections status for the Powerbox and ECU. When a valid frame has been received it turns on. Makes trouble shooting a bit easier.
Jan 16, 2017, 10:08 AM
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I'm new on github and I don't understand howto download the .ino files in order to use with my Arduino software.


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