USB PTT Speaker-Mic for Android
I was looking for a PTT microphone solution that can be used with DVSwitch mobile and Echolink on my Android phone while traveling. But tabing on a cell phone while driving isn't just illegal in most states, it is also extreme bothersome.
Some internet research revealed that IRICO B01 ( Android only) Bluetooth PTT-Mic can be used. So i bought one and found out that the current version beeing sold is the B02 (B01 iOS) version which is for Android and iOS.
Unfortunately i was not able to get the this newer verion to work wich DVSwitch or Echolink.
So i came up with a wired solution using a USB sound card and keyboard emulator packed in an old speaker-mic:
Requiered parts:
Parts can be found on Amazon and eBay.
Schematic:
The USB-Hub is connected to the Android device via the USB-OTG adapter and connects on the other end to the USB-sound card and the Pro-Micro board. The Pro-Micor board emulates an USB keyboard and sends an F12 key code (142) to the Android device when the PTT button (SW1) is pressed. LED1 indicates TX mode.
SW2, Q1 and LED2 are optional used to mute the speaker.
In my case the soundcard was producing a little noise on the speaker output that was noticable backfeeding into the microphone when transmitting. To avoid this, the audio amplifier is turned of by Q1 when the PTT button is pressed. SW2 and LED2 is used as a manual speaker mute function.
The 5V supply for the amplifier and LED's is taken from the USB input of the Hub.
Assembly;
In the first step i removed all housings and connectors to reduce the size of the components as much as possible.
All interconnections have been done by hardwiring isntead of the connectors.
Removed all unusedparts from the old mic PCB and added the volume potentiometer.
It would also be possible to add UP and DOWN puttons to the Pro Micro board and use the Android volume control instead
USB- Hub and Pro Micro board:
Audio amplifier and USB sound card:
