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Apr 30, 2014, 01:20 AM
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averen's Avatar
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MinimOSD Battery and RSSI Help!


Hey All,
I'm working on setting up a MinimOSD from witespy that has the analog pins broken out on the side with some voltage dividers.
http://witespyquad.gostorego.com/min...am-mod-v1.html

Getting it going has been a bit rocky but after clearing the EEPROM and starting over things are going better. Everything coming from the Naze32 (via the serial connection) works fine but I can't seem to get the input voltage and the RSSI feeds to work.

For the battery I'm using a 3S lipo and it's currently reading 7.4V in the OSD but it's charged to 11.3V. I've adjusted the voltage divider settings and 7.4V is the max that I can get it to read. The battery has a direct line (and ground) to the Bat2 pin of the OSD.

Also I can't seem to get the RSSI to work from my RX. I'm using an FRSky RX which outputs PWM RSSI on pin 2. I have this directly connected to the RSSI pin on the OSD along with a ground reference. Checking the PWM output I get between 0.15V and 3.25V. I realize this is an estimation because of how PWM works, but it does show that it's outputting.

If I run the auto setup for the RSSI I end up with a Min of 0 and a Max around 10 with PWM turned on. With PWM turned off (but with the RX still outputting PWM) I get values of 10 - 150 which seems more reasonable. I just don't know if I should trust them.

Any help is greatly appreciated! I've ran a couple of different firmwares on the OSD. Currently I'm running KV Team 2.2, but I've also ran MW OSD with similar results.

Thanks!
Jared
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May 31, 2014, 12:06 AM
Registered User

witespy minimOSD voltage


Quote:
Originally Posted by averen
Hey All,
I'm working on setting up a MinimOSD from witespy that has the analog pins broken out on the side with some voltage dividers.
http://witespyquad.gostorego.com/min...am-mod-v1.html

Getting it going has been a bit rocky but after clearing the EEPROM and starting over things are going better. Everything coming from the Naze32 (via the serial connection) works fine but I can't seem to get the input voltage and the RSSI feeds to work.

For the battery I'm using a 3S lipo and it's currently reading 7.4V in the OSD but it's charged to 11.3V. I've adjusted the voltage divider settings and 7.4V is the max that I can get it to read. The battery has a direct line (and ground) to the Bat2 pin of the OSD.

Also I can't seem to get the RSSI to work from my RX. I'm using an FRSky RX which outputs PWM RSSI on pin 2. I have this directly connected to the RSSI pin on the OSD along with a ground reference. Checking the PWM output I get between 0.15V and 3.25V. I realize this is an estimation because of how PWM works, but it does show that it's outputting.

If I run the auto setup for the RSSI I end up with a Min of 0 and a Max around 10 with PWM turned on. With PWM turned off (but with the RX still outputting PWM) I get values of 10 - 150 which seems more reasonable. I just don't know if I should trust them.

Any help is greatly appreciated! I've ran a couple of different firmwares on the OSD. Currently I'm running KV Team 2.2, but I've also ran MW OSD with similar results.

Thanks!
Jared
Hey Jared.. I'm having the same issues. I cannot for the life of me get my voltage to read correctly. I move up the divider as high as possible and it still won't get high enough to show my actual voltage.

HAve you managed to get this working? I am debating either waiting for kvosd gui 2.3 in hopes it has a workaround built in, or trying to tinker with the code in ARDUINO. I can't find details on this anywhere. Please share the wealth if you manage to find a solution! -- infotechsailor (okdrones.com)
May 31, 2014, 12:13 AM
Words...
averen's Avatar
Thread OP
I found that setting the voltage reference to "EXTERNAL" seemed to work ok but I'm not entirely sure how accurate it was. This did allow me to get in the correct voltage range though. In the end I just decided to plug the battery into the Naze32 and get the get the voltage from the naze through the serial connection to the OSD. This is very accurate and "just works."

Jared
Jul 08, 2014, 07:32 AM
Registered User
Quote:
Originally Posted by averen
.....
If I run the auto setup for the RSSI I end up with a Min of 0 and a Max around 10 with PWM turned on. With PWM turned off (but with the RX still outputting PWM) I get values of 10 - 150 which seems more reasonable. I just don't know if I should trust them.
.......
Thanks!
Jared
Jared
can you tell em plz if u solved this or found out this to be accurate ?
i have exactly the same without PWM set ON i get range to 153
and i am not sure if it correct either.

Using now 2.3 but issue is the same
Jul 08, 2014, 07:38 AM
Words...
averen's Avatar
Thread OP
Quote:
Originally Posted by contact303
Jared
can you tell em plz if u solved this or found out this to be accurate ?
i have exactly the same without PWM set ON i get range to 153
and i am not sure if it correct either.

Using now 2.3 but issue is the same
No, those values are not accurate. The PWM that the DR4-II (and other FrSky RXs) outputs is too fast for the Atmel chip on the OSD to decode. So PWM won't work. Setting it to analog won't work either as the Atmel chip is fast enough to decode either ground (0) or 5V (255).

Essentially to use RSSI with the OSD from the FrSky you'll need to build a Digital to Analog Converter. I haven't tried this (as I've moved to OpenLRS which outputs much nicer RSSI). But this gives some info on how to build a very simple RC (resistor-capacitor) filter DAC specifically with the FrSky Receivers. https://code.google.com/p/minoposd/wiki/AnalogRSSI

Hope that helps,
Jared
Jul 08, 2014, 08:30 AM
Registered User
Yes i guess i have to build one /Looks easy peasy ..I shall try .
Because its so inaccurate as u said it goes to 40 Beeps for no reason at 200 meters then goes back to 90 etc etc .
not really nice if u get worried all the time and its for no reason .
So here is what i build, for my NAZE32 board
http://fpvlab.com/forums/attachment....2&d=1400097197
Jul 08, 2014, 08:42 AM
Registered User
MMH so which is it ? 47 or 100uF capacitor ?
The google code page u linked shows different resistors and capacitor then the diagram ....
I go with the fpvlab Diagram ..Lets see what happens
Jul 08, 2014, 10:44 AM
Registered User
Fixed found solution in other forum
Last edited by contact303; Jul 15, 2014 at 02:13 PM.
Aug 14, 2014, 04:56 AM
Registered User
AlistairR's Avatar
Wondering if you sorted the voltage problem. I'm using the minim with an afro mini so I can't monitor voltage through the flight controller. Having trouble getting it the show the correct range value. It's from white spy on 4s
Aug 18, 2014, 05:36 AM
Registered User
Hey Jared,

I just wanted to ask you how you got the RSSI working. I'm also getting mine from a FrSky D4R-II feeding into a KV-modded MinimOSD, but I was under the impression that the KV mod already puts in the necessary ADC on the RSSI pin to read the PWM correctly? Could you tell me how exactly you wired and set up your OSD to get the correct readings?

Thanks!
Aug 18, 2014, 05:39 AM
Registered User
its trial and error on the values untill it reads correct
.
I use this diagram to connect it ...
Aug 19, 2014, 08:32 PM
Registered User
AlistairR's Avatar
What about correcting battery voltage readings? I'm having the same issue as mentioned in the first post where it doesn't matter where I put the voltage divider slider I cant get the correct voltage value displayed
Aug 20, 2014, 05:19 AM
Registered User
voltage i let my naze32 do ..
plug in and done no set-up needed ..
Like in the diagram


The VI value , Amperage, is a trial and error thing ..Until u find the correct sensitivity for your set-up
Aug 20, 2014, 01:18 PM
Registered User
AlistairR's Avatar
Thanks. I have that working on my naze boards but afro mini doesn't have vbat so it goes straight to minim
Aug 26, 2014, 09:45 AM
Registered User
Well, I've been experimenting with getting my RSSI from a FrSky D4R-II to the Whitespy KV-modded MinimOSD, and here's how I got it to work:

Feeding the RSSI from pin 2 into the OSD as a PWM through the ADC (the TXSSI pin) is a no-go. No usable readings whatsoever.

Running it straight into the ADC as an analog signal (i.e. 'PWM off' in the GUI) kind of works. You'll get a pretty decent reading, but the raw value will jump to maximum signal (which was about 169 with the divider set to 8 for me) constantly. Should you lose signal it'll show on the OSD, but very very slowly. Too slow to be useful, to be honest: only 15-20 seconds after you lose signal you'd get a visual warning...

So, I decided to give the RC filter a go. I connected the RSSI through a 10k resistor to the ADC, which I then connected via a 10uF cap to the GND pin next to it. This makes the signal much smoother and less bouncy. Using the same settings as above (PWM off, divider at 8, max = 169) the reading mimicked the one on my radio perfectly. I set my minimum to 70, which corresponds to around 40% RSSI on my radio.

To summarise: if you want FrSky RSSI on a MinimOSD, get an RC filter!


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