I currently run a Soundcard Fob (USB Soundcard Dongle highly modified) on my 49355 AllStar node. This fob is working great. I need a few more nodes and decided that I do not want to go the Soundcard Fob route due to bad eyesight it is virtually impossible for me to solder thin wires to the surface mount sound chip on the USB Soundcard Dongle. Here is an image of my current Soundcard Fob showing the all the modifications that was done:
Image: Modified Syba CM119 USB Soundcard Dongle
The Allstar Link software needs to interface to the radio in order to control Push To Talk (PTT), recognize when a signal is present on the radio (COS) and also manage the TX & RX audio streams between the Raspberry Pi and the radio. All of these functions are achieved using a USB sound card fob that plug into to the RPi’s USB connectors . The connections to the radio however require wired connections.
As you might expect the RX & TX audio are already part of the sound card as this is the intended function of a sound card. RX audio goes to the Microphone input and the TX audio comes from the sound output (In the case of Allstar we only use the Left channel output). The sound card chip inside the fob has some extra GPIO abilities that we need to tap into for PTT (Push to talk) signaling and COS (COS – “Carrier Operated Signal”, “Carrier Operated Squelch” or “Carrier Operated Switch” or COR Carrier Operated Relay… all the same thing, just different names). You can also tap into the LED functions on the chip.
Enough about the Soundcard Fob. I am busy constructing an experimental AllStar Node that will be using completely different circuitry to effect PTT, COS, DTMF and LED displays. No rocket science here and no designing of PCB's for the sound functions to interface to a radio or repeater. I ordered a few components and cables from a supplier in Johannesburg and the parcel should arrive this coming week.
Once I received all the components I will convert an IRLP Node to operate on AllStar Link, app_rpt, Asterisk and Echolink systems. The IRLP system was introduced in the late 1990's as a way to connect remote repeaters using the Internet, rather than telephone lines or RF links. Since that time, VOIP radio technology has progressed quite rapidly. Several other VOIP systems have come and gone, each with different features and capabilities. Systems such as Echolink and Allstar have surpassed IRLP on every level. For example, IRLP can only support half-duplex audio, and requires an expensive proprietary interface. The IRLP software is closed source, and not compatible with other networks such as Allstar. Echolink and Allstar are both free. Allstar is open source, and Echolink is friendly to other software developers, allowing add-ons to coexist with the Echolink software. AllStar is today far more superior than Echolink. AllStar has better audio quality, functionality and features than Echolink or IRLP. Google is your friend in this regard. Now on to the conversion. No I did not invent this conversion. It was obtained from the AllStar mailing list and thanks must go to K0KN for the info. Modifications will also have to be made to either the usbradio.conf or SimpleUSB which ever is applicable. One other important component is the type of USB Soundcard Dongle for this project. I will be using a Syba CM119 Soundcard Dongle which is capable of much higher quality audio than an analog sound card. Main Components I will be using in this project:
- Raspberry PI Computer
- Syba USB Soundcard Dongle
- IRLP Ver 3 Board
- Cables and Connectors
- UHF Motorola Radio
- 12v to 5v Power Converter
Finally: Updates to follow as the project progresses. There are also a few other options that I will be looking into. One can buy a ready made Soundcard Board from overseas but at the current cost and import fees I personally feel that it is not a viable option to import only one or two boards. I trust that the modification of the IRLP board will result in a far cheaper option and hopefully just as good interface as the Soundcard Fob version. I will keep all those interested posted on my findings.
