Tiny board that allows you to connect the Baofeng UV5R radio to a smartphone or other device that uses a TRRS connector for audio.
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Latest commit bb3cfad Sep 13, 2016 @johnboiles committed on GitHub Merge pull request #10 from azend/patch-1
Fixed typo in resistors

README.md

Baofeng UV5R TRRS Adapter

http://github.com/johnboiles/BaofengUV5R-TRRS

A tiny board, which allows a smartphone or similiar device to connect to the Baofeng UV5R radio via a TRRS audio connector. It allows for connecting the radio to a software TNC app such as APRSDroid or PocketPacket. Solder on the components, solder on the cables, then provide some stress relief, (I use solid-core wire and heat shrink tubing), and you can use your UV5R with your smartphone for APRS on the cheap.

Baofeng UV5R TRRS Adapter Baofeng UV5R TRRS Adapter

Pictures

The PCB and a US quarter The front of an assembled cable The back of the PCB with the cable ends

Notes

A small capacitor and 3 resistors to trick the iPhone into thinking a microphone was connected. This part of the schematic was inspired by this article on connecting Arduino to an iPhone.

A small capacitor on the speaker out of the radio removes any DC bias. (I'm not sure why this was necessary, but in my testing it made receipt of packets much more reliable.)

On my UV5R+, volume is maxed, vox is set to 2 and, squelch is set to 1. On my iPhone volume is also maxed.

Schematic

Schematic

Bill of Materials

Qty Part Notes
1 Kenwood Type Speaker Mic Cable You can also use 2.5mm and 3.5mm cable.
1 3.5mm TRRS Cable
1 10kΩ Resistor 0603
2 2.2kΩ Resistor 0603
2 0.01uF Capacitor 0603
1 3" of 0.25" Diameter Heat Shrink Tubing Optional

How to Order

You can order the board directly through OSHPark ($1.70 for 3 boards with free shipping). Digikey or Mouser are good places to buy the resistors and capacitors.