RS485 meets Radio.

1
RS485 meets Radio.

• Presenting a less-wires approach to automation
  and computer control of radio equipment
• By Kerry Richens (VK1KRF)
• http//www.qsl.net/vk1krf
• Thanks to BB Electronics
• http//www.bb-elec.com

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Preamble

• stick to a microprocessor family and get the most
  out of it
• Modularise circuit boards and designs so that
  they can be used in many applications
• standardise pinouts, layouts, software routines
• A one chip microcontroller can be considered as a
  customisable IC
• eg why buy a 16.00 Stepper motor controller
  when a 1.20 PIC16C56 can do the job
• an 11.00 hex keypad decoder is not a bargain if
  you can do the job better with a 1.20 Micro
• BY the way The PIC acronym "Programmable
  interface controller/Circuit/Chip"
• Don't be affraid to have more than one Micro
  (Customisable IC) on the board
• Too many hardcore programmers out there telling
  us what to do

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Why?

• Automation is what I do
• This project stemmed from my desire to convert an
  old security camera pan/tilt head into a
  satellite tracking rotator
• Ever run out of ports for rotators rig controls
  modems TNCs mouses etc?
• Sick of wiring up 8 wire rotator cables?
• Like home-brewing? (Hic!!)
• Would you like all remote devices on the one cable

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Topics of Discussion

• My Radio Shack/ Workshop
• Background on RS422 and RS485
• Converting RS232 to RS485
• The Benefits of RS485
• Making it Robust
• Programming DDE

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Devices controlled by RS485 in my Station

• Dual Axis rotator with 2m crossed Yagis, 70cm
  Helical, 2.4GHz down converter.
• Hills rotator.
• 2M Phasing Harness.
• 5 port,3 port,2x 2 port remote coaxial relays.
• Preamp bypass relays for 2m, 70cm and 2Ghz.
• FT707 Digital VFO (on the workbench).
• FRG9600 on its own serial port (At Present).

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Phasing harness and preamp control.
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Remote Coaxial Relays
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Dual Axis Rotator

• No calibration pots
• 2 ICs
• Networkable
• No ADC (Explain Pot Command)
• 2nd Order Polynomial linearising in 16 bit
  integer basic

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Background on RS485

• USB, Older 2Mb networks like Lantastic
• Building management, Dedicated print networks
• Security Systems, Camera Control.

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RS485 levels
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Benefits of RS485

• Multidrop 32 devices on a single line without
  boosting
• Runs on a single 5 Volt rail
• Data-rate of 100KBps at 5,000 Feet
• Differential line means it has High noise
  immunity
• Easily implemented
• Can be easily made robust in harsh environments
• The actual data format and type of network can be
  any level of complexity (Master Slave is the
  easiest)

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Converting RS232 to RS485

• There are 2 types of send control systems.
• Automatic
• RTS/Software

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Schematic of my Converter
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The 75176 Line Transceiver

• An example of a simple network

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Active Termination

• When the Master is inactive the line is
  completely tristated.
• The line must be actively forced to a 0 to
  ensure that noise does not present as data to the
  slaves.

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Common Ground Surge Protection

• An example of single wire protection.

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Four Line Surge Suppressor
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Optical Isolation
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Visual Basic and the real world

• A Visual Basic program can send and receive data
  from other programs via Dynamic Data Exchange
  (DDE)
• Visual Basic can send and receive data via the
  MSComm Visual Basic Extension (VBX)

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Examples of programs that support DDE

• Winorbit satellite tracking
• Mixw digital modes
• Microsoft Office

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VB object properties
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My Station Control Panel
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The possibilities are endless

• Weatherstations
• Mast Lights
• Rig control including homebrew equipment
• Power control and monitoring
• Antenna Tuning units
• If it doesnt work, Put a Microprocessor in it
• Imagination is more important than Knowledge