APRS cable for HTC EVO 4 and UV-5R
Thanks to others on this forum, I was able to make a cable to hook my UV-5R into my HTC EVO 4 and use APRSDroid. The EVO 4 has remote control functionality on some headphone sets so you must put a resistor on the mic input in order for it to accept the incoming signal. Some info on it is here, towards the bottom: http://pinoutsguide.com/HeadsetsHead...e_pinout.shtml .
Initially I used separate 2.5mm and 3.5mm plugs to connect into the UV-5R. However they are finicky, so I have purchased the double pin connector from Argent Data to get a reliable connection. https://www.argentdata.com/catalog/p...9i2qnnobce5lg5
The 3.5mm TRRS plug that goes into the phone is available from them as well, however I just bought a few off eBay.
Here's a drawing of the configuration that works for me.
Well, the cable above did not work with the Argent Data connectors. I had to remove one of the grounds. Otherwise the unit transmits continuously. Below is the revised schematic. Now it works great. Anyone else have any issues with this?
with having both grounds there you basically created a ptt switch that was always activated... i did the same thing when i made my cable to begin with...
here is a good one: http://i.imgur.com/mmD4s.png
as is that should work with VOX and if you add a npn transistor between the spk- and mic- lines you can hook an AC source like the right channel of the stereo output to the collector of the transistor you can trigger the ptt programatically instead of relying on the vox.
the diodes prevent the AC audio signal return lines from carrying the signal back to the DC ptt circuit.
i haven't found any reference to the appropriate resistor and diode values but i soldered one up last night and i just need to attach connectors and test it.
update0: i built the circuit and managed to test the receive side of things yesterday and it works. i used some random diodes from a rectifier diode assortment (i think they were IN4001) and some equally random 2.2kohm 1/4W resistors i had laying around.
update1: the above circuit plus npn won't work as the stray RF will keep the circuit in an indeterminate state. it needs to be pulled all the way high (open) or pulled all the way low (closed).
https://github.com/HacDC/AudioToResistance this should be updated to reflect the changes we made last night soon.
for fldigi it works as a right channel actuated ptt and with sound modem it acts as a really fast vox circuit.