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laforge, 02/19/2016 10:52 PM

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[[PageOutline]]
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= Funcube Dongle=
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The Funcube Dongle Pro (FCDP) is a small USB-key-sized low-bandwidth SDR.
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It uses an audio codec as ADC (like many amateur radio projects) and thus can only be used for narrow-band signals up to 80kHz.
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However, for capturing a single TETRA channel, those 80kHz is actually more than sufficient.
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== Hardware ==
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=== Major components ===
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The FCDP hardware seems to be using the following components:
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 * Microchip PIC24FJ32GB002
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  * 16-bit low power microcontroller with Full-Speed USB, 32 KB Flash memory, 8 KB RAM, and advanced peripherals, 28-pin package
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  * homepage: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en536120
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  * datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/39940d.pdf
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 * TI TLV320AIC3104 Low-Power Stereo CODEC with 6 Inputs, 6 Outputs, HP Amp and Enhanced Digital Effects
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  * homepage: http://focus.ti.com/docs/prod/folders/print/tlv320aic3104.html
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  * datasheet: http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=tlv320aic3104&fileType=pdf
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 * Elonics E4000 Zero-IF Low Power CMOS Multiband Tuner (64 to 1700 MHz)
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  * homepage: http://www.elonics.com/products/rf_tuners.do?id=1
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  * product brief: http://www.elonics.com/assets/PB_E4000_10_2009.pdf
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=== Architecture ===
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The hardware architecture therefore is quite simple:
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The PIC24F implements the USB protocol/interfaces for HID (tuning) and audio towards the PC.  It also drives the TI codec and the Elonics silicon tuner via an I2C interface.
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Analog RF data enters the Elonics silicon tuner, where it undergoes zero-if down-conversion to complex I/Q baseband, which enters the TI audio codec where it is digitized using left/right channels for i/q.  The resulting digital audio stream is passed to the PIC24F, which forwards it via USB to the host PC.
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{{{
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#!graphviz
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digraph G {
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  graph [ rankdir = LR ]
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  Antenna -> "Elonics E4000"
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  "Elonics E4000" -> "TI AIC3104" [ label = "I/Q baseband" ]
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  "TI AIC3104" -> "PIC24" [ label = "PCM" ]
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  "PIC24" -> "Host PC" [ label = "USB" ]
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}
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}}}
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=== Image ===
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[[Image(fcdp_pcb.jpg)]]
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== Software ==
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The OsmocomTETRA repository contains a demodulator script called '''fcdp-tetra_demod.py''' that can be used with the FCDP.
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You have to use the 'qthid' application provided with the FCDP in order to tune to the respective tetra carrier frequency.
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