New software driver and interface card for radiotelescope antenna remote control

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The radiotelescope antenna movements can be controlled from a local command pannel on the antenna plateform. However it is more convenient  to activate the radiotelescope from remote sites via Internet. This is why we are developping a driver that can activate antenna motors.  Control driver is based on the API (acronyme for Application Programming Interface) named Instrument-Neutral-Distributed-Interface control protocol (INDI).

We installed the driver and INDI library version 1.7 on a RaspBerry Pi under RaspBian Stretch Linux distro.

The software driver communicates with an interface card that can read antenna angular positions and activate motors. Driver is writen in C and C++ by Dimension Parabole software team (Patrick F1EBK and Bernard F6BVP). It communicates with INDI server using XTML messages upon receiving target coordinates from an INDI client. Astronomy client softwares such as Stellarium and Cartes du Ciel (Skychart) are compatible with INDI API and connect to INDI server via Internet. Experiments are also being performed with KSTAR application under KDE.

The interface card designed by KK6MK et F1EHN has been assembled by Laurent F6FVY. It is used for remote control of radiotelescope antenna motors. Recently the card has been repared by Patrick F1EBK who added an LCD display card useful for software debuging.

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However, although the repared card is able to control the antenna and read its position angles, it is not completely fitted to the radiotelescope for it can only activate four commands. At least three additional commands need to be added : two for fast movements in either AD directions and one for targetting rotation movement. This is why Alain F1CJN (Radio Club de Maison Lafitte) offered to study a new control card based on an ARDUINO micro controller that will be compatible with KK6MK-F1EHN card and will provide the extra necessary commands. INDI driver communicates with interface card through a serial link at 9600 bauds. It is controlled by software messages from INDI server, based on INDI API library set of functions. INDI server is listening on a dedicated port accessible by Internet. Telescope astronomy clients (Stellarium or Skycharts) connects to indiserver via Internet. Using such astronomy client a user can send an order to the radiotelescope for targetting a given radio source. Then another application will possibly activate an SDR receiver for detecting radio signals from space.

Interface card prototype is finished and working perfectly. The LCD screen displays Righ Ascention (AD) changing while antenna is moving. It also displays the commands sent by astronomy client software (PVP means Low Speed +). When the antenna reaches the target coordinates the software sends a command for switching to tracking mode. The antenna rotation is actually still simulated by hexadecimal coding wheels connected to the card. A more sophisticated optic coder telescope simulator is being developped using a Raspberry Pi and a multiport HAT card. The following pictures show the test-bed. Testing has been performed in Folie N4 building near the parabola while *DUUU radio station studio was broadcasting during the day of décembre 11, 2018.

On the left is the rack temporarily removed from the antenna plateform, equipped with prototype interface driven by Arduino micro controler,  a Raspberry Pi supporting 32 ports serial/parallel card, a card holding connections cable towards the rack connectors ; in its own box another RaspBerry Pi running INDI server and a software for optic coders simulation.

The prototype card screen displays command orders received from the driver and the angular values read on 12 ports of each angular position RA and DEC. During the test each of the 12 bits weight 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 and 2048 are successively raised from 0 to 1. LCD screen displays values in hexadécimal. The test was succesively performed on RA and DEC, prouving that software driver is correctly decoding optical coder values and that wiring of connections was performed without error. Click here to look at test-bed video.

Amon supplementary control commands on the new card, are fast speed implementation toward Est and West and target tracking plus remote switch of separate radio preamplifiers or power amplifier. The two following picture show the preamp 1 ON and OFF commands acknowledgements.

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Patrick F1EBK is wiring the radiotelescope control system. Last improvement is on the simulator RaspBerry Pi power taken directly from the rack connection.

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