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OTRSP Antenna Selector
on ATMEL ATmega8 microcontroller


Many new computers don't have LPT port, usually used to control the antenna switch. To bring control via USB (Antenna Selector has internal USB to RS232 converter on FT232R chip), my Antenna Selector uses Open Two Radio Switching Protocol (OTRSP) to communicate with computer.
It is possible to use LPT port to control Antenna Selector, too (BCD option).
Antenna Selector can switch up to 8 antennas. An option is using two Relay Boxes with 4 relays each. In this option the last relay (Relay8) is always ON for antennas 4-7. Look for 8 Relays Box and 2x4 Relays Boxes documents, how to connect relays to Antenna Selector.
Hardware part of project was made using free KiCad software, program for ATMega8 chip was written using Bascom AVR software.
All source files are included.
Antenna selector uses:

  • FT232R chip from FTDI as converter USB-RS232
  • ATMega8 microcontroller from ATMEL
  • TD62783AP as output driver

Schema of the Main Board of Antenna Selector is as follow:

Schema of Display Board:



Below there are some photos of prototype of Antenna Selector:
Main Board PCB (PCB made using thermo transfer method) and Main Board assembled :

Main Board PCB

Assembled main board


Assembled main board - bottom view

Display Board PCB and Display Board assembled :

Display board PCB

Assembled display board - top view

Assembled display board - bottom view

And the final photos:

Display and main boards with flexible cables

Display and main boards - top view

Display and main boards - front view

Antenna selector uses FTDI chip as converter USB/R232. So, for the first, driver for FTDI chips must be installed. It can be found on FTDI page.
If driver is installed, please plug-in Antenna Selector to the USB port and check in Device Manager, which COM port number is assigned to Antenna Selector. This COM port number must be selected in logging software. If port number has big value (Logger32 and WriteLog can use port number up to 16, Win-Test up to 12), it must be changed in Device Manager to lower.
I tested Antenna Selector with Logger32 and Win-Test, but I cannot to configure WriteLog to work with OTRSP (anybody do this?).

Files to download:
Antenna Selector main files
 Zip file consists schemas, PCB files and hex file for ATMega8
 Download file
File version: 1.00, Date: 2013-12-12, File size: 156 kb
  
KiCad projects
 Full KiCad projects for Antenna Selector. All libraries/modules includes, with PCB in PostScript format and 3D visualizations of the boards.
 Download file
File version: 1.00, Date: 2013-12-12, File size: 658 kb
  
BascomAVR project
 Source BascomAVR files with compiled hex file. Fuse bits must be set to $E3 $D9 (4MHz internal clock) during ATMega8 programming.
 Download file
File version: 1.00, Date: 2013-12-12, File size: 26 kb