Voltage on Pixhawk ADC signal pin?

Hi all

Is there supposed to be a voltage on the signal wire of the ADC port with nothing plugged in?

I’ve installed a SF02 on my plane and it works perfectly if I monitor the output analogue voltage. However, I’m getting nonsensical values on the pixhawk when viewing the range on “sonarrange”.

I understood that the ADC is for reading data, yet I’m getting a signal, which of course clashes with the SF02’s output.

Can anyone confirm that they have a voltage on their signal pin of the ADC port?

Many thanks

Have you setup the sonar scaling parameter which is critical to viewing the correct range values in the sonarrange parameter in the MP?

Thanks for replying, yes indeed I have. Even the raw sonar voltage output is haywire and does not reflect the voltage that is supplied by the SF02’s output if I use a multi meter.

Which ADC input are you using?
I am using the 3.3vdc ADC converter input for my sonars.
Have you selected the correct input pins?
On the 3.3vdc ADC virtual input pins 13 (connector pin 4) and 14 (connector pin 2) are the input pins.

I’m using the same port as in the wiki, just behind the LED: plane.ardupilot.com/wiki/common- … nder-sf02/

My pins are also as instructed, pin 14 (physical #2).

I don’t have something on pin #4 though??

See images.

Thank you very much,

The pin 14 input was just there for reference.
Can you post your rangefinder parameters for me to look at?




@heinduplessis, Tom asked me to have a look into your problem.
All your settings seem correct. The only think I couldn’t check is what value of RNGFND_PWRRNG you have set. If its 1 for instance then the SF02 will try to be doing power saving from 1m which could explain things. However its probably set to 0 as that’s the default.

To answer your original question I put a multi-meter across pins 1 (5v) and pin 3 (GND) and sure enough I got 4.68volts. I put the meter across pin 3(GND) and pin 2 (ADC IN) and I get 0.15volts - so 0 effectively.

So I’m not sure what your seeing on you pin 2 - how many volts do you read on it when you have nothing else plugged into that port?

Thanks, Grant.

The RNGFND_PWRRNG parameter only applies to the PWM connected PulsedLight Lidar. It doesn’t apply to the analog Lidars.
The signal pin will be floating when nothing is connected. The SF02 should pull it to the right voltage.
Cheers, Tridge

Thanks Grant, Tridge

I also get a voltage of around 0.03v. I didn’t know that’s acceptable.

I’ve rechecked everything, if I power the SF02 from the ADC port, the output signal voltage fluctuates from 0.1 to 3.3v continuously. If I power it from USB or from a separate UBEC, it works 100%.

Seems like the problem only occurs if I power from the ADC port.

I’ve now powered the lidar from my receiver and the sonaarage is now correct, fluctuates a bit (some centimeters) but it’s much better. I’ll do a test flight and check ranges.

I’m not sure why it’s a problem from the ADC port - there’s a solid 4.95v coming off it. I’ve got two more pixhawks in route, I’ll cross check.

Many thanks for your help debugging!

If your receiver is powered by the Pixhawk (on RCIN pins) then you should not use that to power the SF02. The receiver port on the Pixhawk can not sustain much current, and is not protected against over current. If you draw too much current then it will kill the Pixhawk. I’ve got 3 dead Pixhawks here to prove it :slight_smile:

Oh my 3 dead pixhawks! Lesson learned I guess :slight_smile:

I’m taking it from the same ubec that’s feeding the output rail of the pixhawk, rated 2 amps I think.

Either way, that didn’t solve the issue. It’s more steady but it’s still all over the place.

See attachment.

[attachment=0]2015-03-04_14h47_26 (Small).jpg[/attachment]

I’m ordering a new pixhawk and SF02 today.

I’ve tested again. If I power the SF02 separately, the pin 7 reports exact voltages representing altitude. Happy. As soon as I start up the pixhawk and it shares a ground with the pin 7 signal, the voltage fluctuates wildly.

I’m thinking my pixhawk is faulty.

Does APM currently support the SF02 via the UART as per pixhawk.org/peripherals/rangefin … inder_40_m ?

I would really appreciate help from anyone that has experience in the SF02 for landing…

I’ve received a brand new 3DR PixHawk and STILL the same problem. Voltages read fine from the pin 7 on the lidar until the moment it’s plugged into the pixhawk, then it goes nuts. Without the lidar plugged in, there’s again a (low) voltage on the signal pin of the ADC port. I think that’s what’s screwing up the readings.

Is anyone else using the SF02 successfully with the pixhawk??

I think I’ve resolved the issue after struggling for WEEKS! It appears the low voltage circuitry onboard of the SF/02 is sensitive to RF interference. I have my telemetry antenna about 20mm from it and the video about 100mm. I’ve moved both out to the tail and now I’m within 2cm accuracy, pretty much matching the documentation.

I hope this helps someone.

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