There are several add on boards for the Pi3 and Pi4, such as the NW Digital Radio UDRC-II, that has a full interface for digital operations, including PTT and audio codecs.Īccess to hardware ports is always limited to the user who either is root or has root privileges. 17 of these gpio lines can be used for things like push-to-talk. It has a array of General Purpose Input Output, gpio, lines of a 40 pin in-line header. The Pi series of miniature computers offer a large array of possibilities for controlling devices. This will cause the RED PTT led to flash and the transceiver PTT to toggle on and off. Pressing the TEST button will cause the PTT line to rapidly toggle for a period of 2 seconds. You must test the selected interface as it is not possible to know which is the correct one for the DRA interface. If multiple C-Media devices are discovered they will enumerate as C-Media-A, C-Media-B, etc. The PTT type, the device and the GPIO line must be selected. The circuitry was designed to operate correctly no matter if the Heartbeat has stuck in the on or off state. This will occur if fldigi and similar modem program is not reading/writing audio data. This function will kill the PTT line the audio stream is interrupted. The PTT line on any DRA Series radio adapter is interrupted with the failure of this health status. The Blue LED indicates the health status of the system, and illuminates when everything is okay. If the HB LED stops flashing because the radio adapter or the computer/appliance has failed, or the software has stopped reading or writing audio data, the Blue COMM OK LED goes out. If everything is okay, (HB LED is flashing) a Blue LED called "COMM OK" illuminates. When the Cmedia device is reading or writing audio data, the HeartBeat status LED (HB) flashing. All DRA Series radio adapters include a Heartbeat Monitor. GPIO-3 is used to drive a fully buffered and deadman protected PTT circuit. The Cmedia device supports 4 unbuffered input/output lines, GPIO-1. The DRA-Series digital radio adapter is used for Packet Radio or other digital programs and applications like VARA-FM, VARA-HF, SoundModem or fldigi.Īll RA Series radio adapters include GPIO support. The DRA is a radio optimized sound card used to connect a two-way radio to a computer for digital communications. It is also used in the series of sound card adapters. Cmedia audio codec chips are used in a number of inexpensive USB audio thumbnail devices.
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