miniADSBrx decoder

miniADSBrx is decoder for miniADSB receiver based on FPGA and with Ethernet interface.



The decoder handles RS-485 digital input signal. The RS-485 signal from and power to comparator+receiver+antenna is sent using classic ethernet cable and can be up to 100 meters long, so you can put miniADSB receiver directly on pole of antenna. This reduces signal loss in coaxial cable between antenna and receiver.

Decoder architecture

The decoder is based on FPGA XC3S250E and inside FPGA is a MicroBlaze processor. The processor is running at 48MHz with 64Mbit SDRAM clocked by same clock source. The Ethernet controller is Microchip's ENC28J60, a 10BASE-T controller with MAC (although due to exceptionally large errata MAC is almost unusable). Decoder data can be also received over RS-232 UART.

FPGA decoder board

Gerber files screenshot:


See manual and parts layout and schematics. Also soldering notes are useful (they are in Czech, but with lot of images). For further information visit miniadsbrx yahoo group and/or send me an email. Files section on the yahoo group may also contain newer versions of the files, if I forgot to upload them here (which is highly probbable).


The FPGA schematics, MicroBlaze firmware, documentation of board is free and should be treated as beerware. It means that if you think the decoder is worth of it, when we meet some day, you can buy me a beer. You can modify the code and documents, redistribute it, but you must keep the copyright and license information. Some parts of source code is GPL, espetially the TCP/IP stack (encnet) and includes for the mb-gcc compiler (I suppose).
Important: The MicroBlaze processor and IP cores around it are not free, except those which were made by me, (SDRAM controller, interrupt controller) which are beerware. I do not know wheather I can redistribute compiled ngc files of MicroBlaze or not, but I expect not. This is reason why user cannot recompile the FPGA.
Source files are compiled for MicroBlaze using GNU compiler mb-gcc. It should be freely available on web (though I do not know where).

Kit ordering

Complete kit (see manual) includes all parts plus some spares, PCBs, enclosure can be ordered by email or at this page for 85€ including postage within Europe and PayPal transfer fees. For postage within Czech Republic see manual, as well for non-European countries.

Decoder data

Decoder provides data in several formats, the most notable is "AVR Format". Other formats include binary format, which saves about 50% of bandwidth in comparsion to AVR Format and compressed binary format which is filtered through gzip to save even more bandwidth on slow networks (mobile phone).
The data are provided as TCP stream. Some PC applications (Sprut's adsbScope) can interface directly to the decoder, while others (PlanePlotter) must use a COM port for serial data and null modem emulator must be installed (like com0com).
For more details see manual.

Sample operation

An ADSB-1 board is currently running at Hůrka in Prague (see this link).


zuban2 (at) zuban (dot) name

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