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 Oudie miniUSB pin4 5V instead of 3,3V?
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 22/03/2017 :  11:06:43  Show Profile  Reply with Quote
I have an Oudie 2 which I connected to my DSX.
Initially I sued the cable supplied with the Oudie, but its 5V power supply emits a radio frequency that opens the squelch on my radio.
There are multiple solutions to this problem, but since my DSX also output 5V I thought of uninstalling the Oudie cable and using one of my own cables which I built back when I was using the MIO 400.
I know that the miniUSB pinout of the Oudie is different and am proceeding to change it, but here is the doubt which raised this post:

I know that with Oudie you have to connect pin4 to TTL high (or VCC), which usually is 3,3V, but in my converter the VCC is 5V.
Would there be any problem in connecting pin4 to 5V instead of 3,3V?
Right now my original Oudie 2 cable is in my glider, so not available to measure what voltage is on pin4, but I suspect that it could be indeed 5V instead of 3,3V.

Can anyone shed some light?

Thanks to everyone.

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...

davesalmon
Pterodattilo

United Kingdom
1620 Posts

Posted - 22/03/2017 :  13:25:45  Show Profile  Reply with Quote
We've just had a similar problem, but with a V2 and new KRT2 8.33 radio. Foe some years the V2 has been connected via a GliderGuider interface connected to the 12v supply and to the SN10 vario. The interface supplies 5v and data to the V2. Never had any interferance problems with the old Becker 3201 radio. Immediately on fitting the KRT2 we got very loud interferance when the V2 was switched on and charging. We tried ferrite beads, but finally found that changing the squelch from the recommended 3 setting, to 5, seems to have cured the problem.
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 22/03/2017 :  15:57:33  Show Profile  Reply with Quote
Changing the squelch threshold surely is a solution, but in my current set this would mean uninstall the radio an adjust a screw with the radio turned off.
Obviously it would require some attempts to set the correct threshold and test with the help of some other glider pilot.
Furthermore the interference is not always there, thus I risk to adjust the screw and then after a couple weeks having the problem again.

It would be much better to eliminate the source of interference.
My guess is that the sense pin would tolerate 5V, but if I can obtain some reassurance about that it would be better.

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 23/03/2017 :  00:33:58  Show Profile  Reply with Quote
This evening I made a little test and crossing my fingers I hooked up the 5V to the pin4 on the Oudie.
It worked flawlessly.
My only concern is if in the long run a higher voltage could damage the Oudie.
I wonder what all the different cables out there supply to pin4 for Oudie configuration (Glidertools cable, Oudie own cable or others).
Measuring voltages on the converter I also noticed that the TTL-IN pin of the MAX232 (pin 11 for channel 2 and pin 10 for channel 1) is at a constant 3.1V when the channel is not being used, and tried to connect this voltage to pin4 of the Oudie.
It worked.

Now, since I only use channel 1 in the MAX232 I wonder wether it could be a stupid idea to use the TTL-IN of channel 2 to supply 3V to pin4 on the Oudie.

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...
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Coolwind
Moderator

Italy
8957 Posts

Posted - 23/03/2017 :  01:23:49  Show Profile  Visit Coolwind's Homepage  Reply with Quote
Why 5v ? Can't you lower voltage to ttl level with a resistor a diode anything better than nothing?
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 23/03/2017 :  11:15:02  Show Profile  Reply with Quote
Actually I didn't think of that.

I studied a little and came out with a little circuit like follows:



Pin1 ----------- 5V
|
resistor
|
Pin4
|
zener 3.3V
|
Pin5 ---------- GND

Resistor dimension depends on how much current needs the sense pin4.
I assume very little, in the region of some mA thus resistor can be high, to limit the amount of dissipated power through the zener.
I plan to make some measurements this evening to come up with a number, I expect it to be in the region of 100-300 Ohm (actually, searching on distrelec I came up on some 100 Ohm resistor called "sense" resistor: would that mean something?).

What do you say, would this work?

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...

Edited by - Berto on 23/03/2017 11:33:46
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 23/03/2017 :  16:28:42  Show Profile  Reply with Quote
A colleague pointed out that if the pin4 absorbs close to no current I can simply use 2 high value resistors like this:

5V ------- pin1
|
34KOhm
|
---------- pin4
|
66KOhm
|
GND------- pin5

This way the absorbed current would be minimal.

I got a bunch of resistors and diodes and this evening I will try it out.

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...

Edited by - Berto on 23/03/2017 16:29:05
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Berto
Pterodattilo

Italy
1286 Posts

Posted - 31/03/2017 :  11:48:24  Show Profile  Reply with Quote
Update: mostly anything works.
Connection is established even with just 1.2V on Pin4.

In the end however I had to change approach completely since I found out that the interference was not due to the Oudie converter but from the DSX 5V power supply, thus I replaced the cable and disconnected the DSX 5V out completely.
With this cable, even using the Oudie converter there was no interference (at least for 1 flight).
We'll see how it goes.

Thanks to all.

Marco Bertoluzza
AVM Voghera

... intanto mettilo a terra, poi parliamo dopo ...
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