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Thread: PPM to Analog Converter (For EzUHF RSSI)

  1. #21
    Bazinga! Maximus's Avatar
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    I picked up my PPM to Analog Convertor at the post office today, thanks Michael! Installing was straightforward.
    RSSI seem to work great, but I can't get Link Quality to work on the DragonOSD. The calibration voltage range I can set on the DragonOSD is 0-3.3V, but the Link Quality range is from 3.89-5.1V. I'm okay with using RSSI instead of Link Quality, but if there's a way to get it to work that would be great.

    Edit: how about a resistor in series on the output signal wire? Will that bring the voltage reading down?
    Last edited by Maximus; 9th February 2012 at 05:10 PM.

  2. #22
    Michael Mictronics's Avatar
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    Click image for larger version. 

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    You can use a voltage divider for that purpose.

    R1 shall be 47KOhm and R2 100KOhm. This will result in 3.3V output to the DragonOSD when the input is 5.1V.

    If you use SMD resistors this mod should be possible directly on the converters PCB.

    By the way, which channel to you use to output the RSSI or Link Quality? Hopefully not ch8?

  3. #23
    Bazinga! Maximus's Avatar
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    I did use channel 8. I saw something in a post about channel 8 doing something funny and that Sander is mucho embarrassed about it and will release a fix soon. I didn't expect it to cause issues with RSSI/LQ readings as well. Does it?

    Thanks for the solution. Is the bottom wire the ground, and the top wire the signal? Should I wait for the firmware fix which will solve the voltage issue, or does it not affect it? I'm using up all other 7 channels, and feel very geeky flipping switches and turning dials on my Tx!

  4. #24
    Michael Mictronics's Avatar
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    Up to to EzUHF RX firmware v1.24 the ch8 has an offset of 300us. As far as I know this will affect also the RSSI/LQ output. At least I saw a timing up to 2.3ms when it should only 2ms max. You can just temporary check against ch7 for example.

    Although the voltage problem will not be solved with the RX firmware fix. Since at 2ms PPM timing the converter will output 5V. So you need the resistor divider in any case.
    Regarding the above image, yes, ground is bottom and signals go in and out at the top wires.

  5. #25
    Bazinga! Maximus's Avatar
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    Thanks, will do the voltage divider and test ch7. What do I look for compared to ch8? A different voltage output level?

  6. #26
    Michael Mictronics's Avatar
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    Yes, the voltage on ch8 should be higher than ch7 at 100% LQ.

  7. #27
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    Hello Michael or anybody who can help me

    Could you confirm some readings for me please?

    I connected the converter to the EZuhf receiver and channelled CH8 to the quality signal and MK is selected

    My readings are: TX on- 4.0V TX off- 1,9V
    Does this seem right?

    On your video I see 1,9 but when TX on I see 4,99.



    I just read the last few threads but what is going on with channel 8?? don't get it really.
    Thanks

  8. #28
    Michael Mictronics's Avatar
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    The output voltage is not that critical, it depends also directly on the supply voltage of the converter. Just calibrate your OSD RSSI to min and max if such feature exists.
    You can also try to connect the converter to the throttle channel and check the readings. You should archive an almost full voltage swing. The rest depends on the timing of the EzUHF RSSI and LQ output.

    The problem with ch8 is a 300us offset in timing up to RX firmware v1.24. The bug is already fixed but it seems a new version is not yet released.

  9. #29
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    Quote Originally Posted by Mictronics View Post
    The output voltage is not that critical, it depends also directly on the supply voltage of the converter. Just calibrate your OSD RSSI to min and max if such feature exists.
    You can also try to connect the converter to the throttle channel and check the readings. You should archive an almost full voltage swing. The rest depends on the timing of the EzUHF RSSI and LQ output.

    The problem with ch8 is a 300us offset in timing up to RX firmware v1.24. The bug is already fixed but it seems a new version is not yet released.
    Thanks Michael,

    When I connect is to the throttle channel I DO see the ~5V as a max.
    So should I put 5v as the max in the OSD? (yes, min and max V I can put in the OSD)

    Or do I need to keep the 4V as a max; Tx next to the RX I see the 4V .... (or is this 1V the difference or the 300us 'error'?)

  10. #30
    Michael Mictronics's Avatar
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    You need to put in the voltages you see with the RSSI, so the 4V is max.

    But, as soon as a new firmware for the EzUHF RX will be relased, which addresses the ch8 bug, then you might need to do a calibration of the OSd again, because the max voltage will be slightly lower then, and so will be the min.

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