No RSSI with Naze32 and FrSky Delta 8 -- RESOLVED

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Crady
Posts: 11
Joined: Wed Oct 08, 2014 4:47 am

No RSSI with Naze32 and FrSky Delta 8 -- RESOLVED

Post by Crady »

I'm setting up a Naze32 for the first time and have run into a snag; I'm not getting an RSSI reading from the Rx.

Gear:
    Full Naze32 - latest firmware
    Baseflight - Windows 7 Ultimate
    FrSky Delta 8 in CPPM mode
    Naze32 set to read RSSI on AUX 3
    FrSky RSSI output connected to AUX3
    AUX 4 is connected to a servo and is functioning
    In the CLI I have gimbal_flags = 4 and rssi_aux_channel = 3
    AUX 1 and AUX 2 are unassigned/unused
    Note: KV OSD on order but hasn't arrived yet

I've tried connecting the FrSky RSSI output directly to the Naze and through an RC filter but Baseflight always shows 0%.

I don't have a scope, but if I measure the RSSI output frequency from the Rx I get 197 Hz (rate too slow for the Naze?).

As an aside, if I use an RC filter on the RSSI output of the Rx I get the expected range of 0v to 3v.

I'm guessing the RSSI frequency is too slow but I have no way to test that.

Ideas?

Thanks!
Last edited by Crady on Tue Oct 21, 2014 8:06 pm, edited 2 times in total.

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Crady
Posts: 11
Joined: Wed Oct 08, 2014 4:47 am

Re: No RSSI with Naze32 and FrSky Delta 8

Post by Crady »

I received a response from 'geebles' on the RC Groups forum that solved the mystery. As I suspected the Naze32 cannot read the FrSky PWM RSSI data however, there is a workaround in that you can configure a pin on the Naze32 to accept an analog RSSI voltage via the CLI using set rssi_adc_channel = 1. This reconfigures the Naze32's RC Channel 2 pin to be an analog RSSI input (I'm using the Delta 8 in CPPM mode which frees up the unused Rx input pins on the Naze32).

After that I installed an RC low-pass filter (effectively a PWM to proportional DC voltage converter) between the PWM RSSI output of the FrSky Delta 8 and the newly configured "analog RSSI input" of the Naze32.

The final step was calibrating the percentage scale produced by the Naze32 using rssi_adc_max (a 100% reading) and rssi_adc_offset (a 0% reading) in the CLI. The range of both values can be anything from 0 to 4096.

:D

hndaluvr
Posts: 4
Joined: Tue Oct 07, 2014 1:36 pm

Re: No RSSI with Naze32 and FrSky Delta 8 -- RESOLVED

Post by hndaluvr »

Crady,
I'm working thru the same issues that you've encountered. Having never built an RC filter for one of these applications, what values for resistor and capacitor work best for this setup? If you could list part numbers that would be GREATLY appreciated.

Thanks!

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Crady
Posts: 11
Joined: Wed Oct 08, 2014 4:47 am

Re: No RSSI with Naze32 and FrSky Delta 8 -- RESOLVED

Post by Crady »

Hi,

The values that worked for me were 10uF and 1K ohms, though capacitor values as low as 1uF should work but you'll need to increase the resistance value to 10K ohms. Be aware that longer RC time constants would likely result in sluggish readings.

As an aside, I've since added a MinimOSD w/ KV Team Mod v1.0 from Witespy/Ready To Fly Quads.

It was only $11 and if you use it with the MultiwiiOSD r1.2 firmware it will read the FrSky PWM RSSI signal directly — no RC filter required.

As a bonus, the firmware provides a slick auto-calibration routine.

Cheers!

Crady

Finished RSSI RC filter
Finished RSSI RC filter

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