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Can't create my own headset for Android phone

Discussion in 'Audio' started by Hyerman, Jun 30, 2020.

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  1. Hyerman

    Hyerman

    4
    0
    Jun 30, 2020
    Hi,

    This is my first post on this forum. My apologies if it is the wrong section or I get anything wrong.

    I am trying, and failing, to create a simple headset for an android phone out of basic components. My design only has one speaker rather than the two that a headset normally has. It also doesn't have any of the fancy control buttons. It just has a single speaker and a microphone.

    The android spec for audio pugs can be found here. https://source.android.com/devices/accessories/headset/plug-headset-spec#electrical
    The jack side of the android spec can be found here.
    https://source.android.com/devices/accessories/headset/jack-headset-spec

    The datasheet for the microphone I have been using can be found here.
    https://www.cuidevices.com/product/resource/cme-1538-100lb.pdf
    The datasheet for the speaker I have been using can be found here. NOTE: this is a link to a pdf download rather than a web page.
    https://www.soberton.com/wp-content/uploads/2018/07/SP-1003-June-2018.pdf

    The CTIA wiring for 3.5mm plugs is described rather well in this post.
    https://electronics.stackexchange.c...controls-do-not-work-after-4-pole-jack-repair

    I wired my headphone up the same way as the CTIA diagram in the prior link with a few exceptions:
    1) I only used one speaker rather than two. I wired up the right speaker and not the left speaker.
    2) I added a 110 ohm resistor in front of the speaker so that the combined resistance on that line would be 117 ohms. The android plug spec indicates that the resistance should be between 32 and 300 ohms.
    3) I added a 520 ohm resistor upstream of the microphone so that the combined resistance on that line would be 1120 ohms. The android plug spec indicates that the resistance should be greater than 1000 ohms.

    When I plug in my headset I get nothing. Nothing comes thru the microphone or out thru the speakers. My phone will continue to use its built in speakers and microphone. I also use an app that detects and indicates headphone insertion. An app that works pretty well to determine if a headset with-or-without a microphone is attached is called “Headset Notifier” on Google Play. I turn off all the options for it so that it only comes on when I want it to.

    For comparison, I have a cheapo Skull Candy headset with a microphone. It works great in my android phone.

    I checked the resistance of the various plug contacts on both my headset and the Skull Candy headset. I see what I expect on my headset. The Skull Candy headset has infinite resistance on the sleeve connections, which I don't understand. Resistance between the Mic and the ground is 1120 ohms.

    I appreciate any guidance that can be provided. I am a software person, but 30 years ago I had an aerospace engineering degree and took basic 200-level circuit courses. My understanding of your comments won't go much beyond that.

    Thanks,

    Hyer
     
  2. ramussons

    ramussons

    356
    66
    Jun 10, 2014
    There is something fundamentally wrong. Forget the Resistance, speaker.... etc.
    If you plug in a 3.5 mm jack into the phone, the internal speakers must cut out. Even if its only a dummy plug.
     
  3. Hyerman

    Hyerman

    4
    0
    Jun 30, 2020
    ramussons, you are not correct. Smartphones do not physically check for the plug. They check for electrical resistance. You can see that in the android plug spec that I included a link to.
     
  4. Martaine2005

    Martaine2005

    2,751
    742
    May 12, 2015
    My smartphone has a TRRS 3.5mm connector.
    The speaker cuts out when the headset is plugged in or a dummy TRRS jack. Just tried it.
    Then again, is the iphone 5 really smart?.

    Martin
     
  5. ramussons

    ramussons

    356
    66
    Jun 10, 2014
    AFAIK, the intelligence of the "controls" on a headset is only on the 2nd ring resistance - the mic line. For a "headphone only" setup, the 2nd ring is same as the sleeve, the ground return. The smartphone "understands" that a pair of "only" headphones is plugged in and acts accordingly. Maybe ( I have not tried this) if a 2 ring plug is used with the 2nd ring left unused, the phone my not sense the plugging in.
     
  6. Hyerman

    Hyerman

    4
    0
    Jun 30, 2020
    The CTIA pinout is this:
    Tip - Speaker Left
    Ring1 - SPeaker Right
    Ring2 - Ground
    Sleeve - Microphone

    I have tried:
    1) a 22 ohm resister between Tip and Ring2 and a 22 ohm resister between Ring1 and Ring2
    2) a 150 ohm resister between Tip and Ring2 and a 150 ohm resister between Ring1 and Ring2

    I have tried these combinations with TRRS plugs from three different manufacturers.

    They all show the correct impedance between Tip and Ring1 and Ring2 but none of them work when plugged into my android phone.
    I determine if it works on my android phone in two different ways. First, I have an app called "Headset notifier". It pops up and says whether the detects a headset (with or without a mic). The second way I test it is by adding a speaker (8 ohms) to one of the channels and seeing if music will play.
     
  7. ramussons

    ramussons

    356
    66
    Jun 10, 2014
    Why not try only the headphone setup? Tip/Ring/Sleeve plug, only for the Right/Left outputs.
    The "sleeve" part is not standardised. I have come across "official" headsets of LG, Sony, Nokia, Micromax, ... where there are buttons that perform different functions - Connect Disconnect calls, Start/Stop/Skip playback, Vol Up/Dn, .... And these headsets function well on all phones as far as listening is concerned. The other functions are proprietary to each phone. The controls may function (if they do), but with different results.
     
  8. Hyerman

    Hyerman

    4
    0
    Jun 30, 2020
    My headset works now. For the benefit of anyone else who has the same problem.
    - android sees the headset (without a mic) being attached if ground and mic (ring2 and sleeve) are shorted.

    - android see the headset also having a mic if ground and mic have reasonable resistance across them (I have tried 1K, 1.5K, and 1250 ohms). I have not tried any other resistance to simulate button presses.

    - my mic and speakers work fine with a 8 ohm speaker and a 1250 ohm mic. The datasheets for both of them are above. It records my voice fine and I can hear the speaker in my ear. I have only hooked up one speaker and android doesn't seem to care if I use one or two speakers.
     
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