20 decembrie 2012

Android Digimodes Interface Diagram

OK, OK, don't start to teach me to use a CAD software because I 'm too old for that and I am not an engineer but attorney!

I made a nice interface for using my HTC Desire S for HF Digimodes as it's piece of junk as a phone...
The schematics come in two versions, one is of extreme simplicity but the second has to be fine tuned to work with the phone.
As you may know, the Android phone is made to be also a music player so it has a stereo output. This is the key for making the PTT circuit. One channel is for modulation and the second one is for detecting and for PTT circuit. I used a double detector to have a sufficient voltage to trigger the 2n2222 PTT transistor, in Open Collector circuit. If you transceiver use a negative voltage for PTT, the schematic is simple to transform.

The second version use the same circuit for audio In/Out but have a small preamplifier for the audio before the detection is made. This is suitable for low volume Android devices and uses the approximative 3 V from the microphone. The input of the Android device is not using a condenser microphone, therefore we can use that DC.
The preamplifier is made with a 2N2222 transistor and it may be necessary to tweak the positive polarisation for a better result.

As a response to a comment from Catalin, YO3FVR (TNX!) , I must admit that, indeed, there is a error in the HTC connector! 
From ring to tip, the sections are:
-Microphone / Control / AUDIO IN

So, I think this answer to your question!
Many thanks for notice me about this!

Un comentariu:

YO3FVR Ham Radio Pages spunea...

Salut !

Te deranjez cu o nelamurire: pe cele doua scheme, observ ca pinul "sleeve", cel mai apropiat de mufa Android, este legat la masa.

Eu folosesc pt. interconectarea unui MAAS AHT-2UV cu telefonul Android (LG Optimus Black sau HTC Gratia) o configuratie in care pinul "sleeve" este intrarea de microfon, iar masa este exact pinul urmator.

Configuratia pinilor am luat-o de pe dar am si verificat-o cu un adaptor de la 4 pini la 3 RCA. Configuratia functioneaza foarte bine, doar ca eu nu folosesc PTT, ci ma folosesc de functia VOX a transceiver-ului. Aplicatia utilizata este APRSdroid...

Ce as dori sa te intreb: este posibil ca la HTC Desire S sa fie alta schema a mufei de 4 pini? Ai cumva un link catre o pagina in care este descrisa schema pinilor?

Te intreb pt. ca am incercat la un moment dat cu un Desire S si nu am reusit si nu am inteles de ce...

TNX & 73!
Catalin, YO3FVR

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