johnboiles / baofenguv5r-trrs

Tiny board that allows you to connect the Baofeng UV5R radio to a smartphone or other device that uses a TRRS connector for audio.

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.

Pictures

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.)

A 100Ω resistor is employed to improve detection on a variety of Android phones.

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

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
1	0.1kΩ 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.

Thanks

The following people have provided contributions to this design

• kronicd VK6HAX - optimisations to improve detection on a number of phones

baofenguv5r-trrs's Issues

Question about Ground Connection

I noticed on your schematic the ground is connected to the tip on the trrs plug which is one of the audio out channels. Is this the correct place to connect the ground or should it be the 2nd ring from the bottom?

Finished product?

Can you post pictures of the finished project?

Parts List on Mouser

John, I want to say thanks for designing this little PCB and identifying the components and connectors.

I have a project where we plan to track an APRS device on a high altitude balloon, and we plan to have a number of Baofeng radios connected to Android phones running APRSDroid.

I've quickly selected the resistors & capacitors and made a Mouser project with the components. This is enough parts for 10 boards, plenty if you make any mistakes. As mentioned in other issues - this is SMD soldering and these are small 0603 parts, so be prepared for that. Personally, I will likely reflow these boards using a hot plate.

Mouser project:
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b33edb430a

Feature request: Include circuit readings for troubleshooting?

I made one of these a few weeks back but it doesn't quiiiiite work. The audio is way too quiet and close to being overdriven. But I'm not too good with circuits.... Would it be possible to post end-to-end resistance readings or something that might help folks confirm they got their cable right?

Why doesn't the speaker output from the phone have to be voltage-divided?

Aren't we sending a lot of power into the handheld's microphone? Seems like this voltage division should happen on both the HT speaker -> phone mic and phone speaker -> HT mic...

Or is the HT mic input meant for this kind of thing?

Latest version of the shared board on OSHpark does not match latest board on the github project

The latest revision to the board on github, where R4 was added, is not reflected on OSHpark's shared repository. The boards I just received from OSHpark say 'r3' on the back side, but the front side appears to be prior to when R4 was added on github.

Continuous transmit

I'm working with the developer of pocketpacket to see if it's software based but here's my issue. I've used your board (thanks!) to make up the cable. I've tested it for continuity and all good. When I plug it into my iPhone 4, it appears to transmit for long periods. Any troubleshooting I should do on my soldering / assembly?

Remove the need for C2 and correct C1 value.

The notes say that it is uncertain why C2 is necessary, this is because the value of C1 is incorrect, in fact it doesn't match the value used in the link provided. An AC simulation of the circuit gives:

This shows that the input signal is sitting on the shoulder of the high pass filter. Removing C2 and using 200nF (as given in the link) for C1 gives us the correct response for the frequency range we need, it no longer sits on the shoulder. We now have a signal that has uniform attenuation across the band of interest, and the decreased attenuation will make it easier for the phone to pick up

For my design I used 10uF for C1 (with C2 removed), which gives us the full audible range from 20Hz upwards. As for R4, the Android spec says the line should be loaded between 32 and 300 Ohms, dunno what's up with that, but here we are.

To comply with the spec, I use a 270/30 divider here (from phone to radio), with another 10uF cap to the output, just to be safe. This combination gives us about the same frequency response as for the input side. I haven't investigated this fully though. The cap probably isn't needed but let's do DC block just to be safe.

Note that the 10k on the output of this divider is just to simulate the radio input impedance.

Android?

hey!
this board will work same for android?

Vox

Is this the type of adapter the will use VOX on the Baofeng, or does this cause keying ? I've really looked in a lot of places , and haven't found any answer.

more info please..

may i know how is the trrs connected to the pcb since theres only 3 soldering point andhow do i make it for android (nexus 7 3g 2012) tablet?

BaofengUV5R-TRRS PCB

Hi John.. Your BaofengUV5R-TRRS PCB arrived here this morning, 7th January 2017. Many thanks!

If you intend to upgrade the assembly instructions on that PCB, perhaps a photo of the bare PCB with components already installed on it might also provide improved information for those of us a bit cautious about barging in without first have gained a complete picture (i.e. a photo) of the assembled PCB.
It seems clear that YOU knew what you intended the component placement to be but the photos and information you have provided along with the complete and working PCB (and the schematic diagram) would be somewhat easier to immediately understand if the shrink wrap tubing was not there or additional photos were also provided of the populated PCB.

Happy New Year, and thanks again.

Robert, ZL2ROB, (QTHR)

Parts list

This isn't an issue, but I didn't want to create a Wiki until I was sure this worked.

I created a Digikey shopping cart that contains all of the parts (except the board itself) that you'll need to build this, including the heat shrink tubing. The URL is http://www.digikey.com/short/05zht

Digikey didn't stock the Kenwood K1 plug so instead I included a 3-wire 3.5mm plug and 3-wire 2.5mm plug.

I haven't actually built the device myself yet (I just placed the order), but I'll post another comment and/or create a Wiki page once I've received all of the parts and assembled my working adapter.

The only parts that cost more than a few cents are the three plugs, and you can probably cut up some existing cables and use those plugs though that could make the soldering a lot harder. Since the minimum order for the board itself is three, I recommend you get extras of at least the capacitors and resistors (since they cost pennies) in case you screw up. If you end up with extras, just build an extra cable as a backup, give it to a friend or maybe sell it on eBay to someone who can't be bothered to learn to solder.

Many thanks to John Boiles for posting the instructions!

Connecting headset and phone

Forgive me, I'm new to this whole ham thing and I'd like to run motorcycle groups comms through the one band on the ham and arps on the other. Is this possible with a BaoFeng UV-82HP and your PCB?

Sorry for filing an issue, but I didn't see any other way...

Vox Triggered, phone not charging.

When I enable vox on the radio it automatically opens the mic. Happens at any vox setting other than off. Happens when any program, including PocketPacket uses the speaker. Board is built as described on this site.

Could you please share clear pictures of wiring ?

From the pics included its not clear which wire goes exactly where (because of shrink wrap)
If you could include a schematic with respect to the board and wire colors it will be great help.

VOX gets triggered when iPhone is charging

This is probably because noise from the charging circuit comes through on the UV5R's microphone line since the microphone line is not connected.

Possibly bringing back the diode could help this, but was a hack all along, so I'm hesitant to re-add that.

A fully opto-isolated solution would definitely fix the problem, but that'd make for a much bigger board.

If anyone has any better ideas, I'd love to hear them.

Issue using with headphone jack lightening adapter

Thank you so much for making this available! I've used this successfully with an iPhone 5 and iPhone 6.

However, I'm not able to use it with the new audio jack lightening adapter. Whenever the PocketPacket app is running, the radio stays key'd up and transmitting the whole time it is connected to the phone. Have you seen this issue too?

I'm not sure if this is an issue with the PCB or with how the audio jack lightening adapter works.

Any help is appreciated. Thanks!