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I want to implement push to talk on my custom PCB.

I apply a 2V DC bias on the microphone line of the jack through a 2.2k resistor. While pressing the button of the headset I see the resistance between MIC and GND fall to 1.3ohms (I guess the exact value will change with different headset.)

My question is:

Can I still use the microphone while the button is pressed? If I can can you tell me if I can directly send the MIC to my MCU (for detection of the button) and to my microphone amplifier.

I've read the Android documentation but I didn't answer my question.

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  • \$\begingroup\$ Are you using a standard Android headset? \$\endgroup\$
    – JRE
    Feb 7, 2022 at 12:40
  • \$\begingroup\$ Yes It's a standard headset by Sony compatible with Android, It only got a button (function A on the drawing in the first answer) \$\endgroup\$
    – VicMac
    Feb 7, 2022 at 14:23

1 Answer 1

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enter image description here

Figure 1. Source: Android.com

Can I still use the microphone while the button is pressed? If I can can you tell me if I can directly send the MIC to my MCU (for detection of the button) and to my microphone amplifier.

According to Figure 1 pressing Button A will short-circuit the microphone. You will get no audio from the mic while the button is pressed. The MCU can detect the button press by the monitoring Veq which will fall to zero.

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  • \$\begingroup\$ I've read the doc it seems that I can't do push-to-talk this way, I want to know if another way exist \$\endgroup\$
    – VicMac
    Feb 7, 2022 at 14:24
  • \$\begingroup\$ If the button in the headset shorts out the mic signal then you can't. \$\endgroup\$
    – Transistor
    Feb 7, 2022 at 14:32

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