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Radio Equipment => 2.4Ghz 35Mhz => Topic started by: chris-s on February 04, 2014, 11:09:02 PM

Title: FrSky X8R RSSI Output
Post by: chris-s on February 04, 2014, 11:09:02 PM
I was just looking over the specs of these receivers and noticed that the rssi output is now an analog voltage unlike its predecessors which gave a pwm output.

I hadn't noticed anyone else mention this and had just assumed it was still pwm.

I've got one in my unfinished skywalker, originally I fitted a D8R-II which I used a rc filter to convert the pwm to analog and after swapping it out for the X8R I left the filter in place, guess I can remove it and recalibrate the rssi on the minimosd now.

Chris

Title: Re: FrSky X8R RSSI Output
Post by: CurryKitten on February 04, 2014, 11:16:10 PM
It's not analogue, it's PWM.  The original manuals and specs said it was, but they've been re-issued, and it's definately PWM.  I know having plugged it into an OSD expecting analogue voltage, and having it basically not work.

I wrote to FrSky and asked them what was up - who just said, it's PWM, and sent me a screen shot of a capacitor and an resistor wired up as a filter.
Title: Re: FrSky X8R RSSI Output
Post by: chris-s on February 05, 2014, 09:09:12 AM
Ok, thought it a bit odd why I hadn't previously read about it. Guess I'll leave my rc filter in place then.

Cheers

Chris
Title: Re: FrSky X8R RSSI Output
Post by: rob.thomson on February 05, 2014, 09:37:29 AM
It's one of the things that annoys me.

Why not just do a voltage!

Sent from my GT-I9300 using Tapatalk

Title: Re: FrSky X8R RSSI Output
Post by: skyscraper on February 05, 2014, 11:35:07 AM
Quote from: rob.thomson on February 05, 2014, 09:37:29 AM
It's one of the things that annoys me.

Why not just do a voltage!

Sent from my GT-I9300 using Tapatalk

Various reasons.

1 the mcu may not have a DAC.
2 If it does have a DAC then its output will need a buffer amplifier to drive down long lines. More expense and bigger pcb.

Digital output are much less fussy and can provide a reasonable good current output direct from the MCU port in most cases.

You did ask  :)

regards
Andy