GPS - RS232 Switch - DSP-10
Accurate DOS Computer Time Setting
for the DSP-10
The object of this project is to use GPS satellite data to automatically set your DOS Computer clock during DSP10 operation.
This switch is controlled by DSP10 software ver 3.80 or later and will switch your DOS computer between the DSP10 and a GPS satellite receiver and is used to set the DOS Computer Clock to GPS standards automatically. Two auxiliary serial ports have also been provided future expansion. The original concept design was by Johan Forrer KC7WW and finalized by Jimmy Oldaker W7CQ. DSP10 Software is by Bob Larkin W7PUA and will work with both the DSP10 EZKit Lite and the DSP10 DSPx.
The PCB layout provides for a computer software controlled DPDT relays to switch the computers serial port between the DSP10 and a GPS receiver or and can be expanded to 4 relays to control AUX1 and AUX2 serial devices. The GPS MUST provide a 1PPS (One Pulse Per Second) output and serial output data can either be NMEA output or Motorola UT+ binary output.
The RS232 Switch and DSP-10 software have been tested on the Motorola Oncore UT+ using its binary TTL outputs with the Shera GPS Frequency Standard board providing TTL to RS232 conversion but the UT+ needs TTL to RS232 conversion of its 1 PPS to work as a stand alone GPS engine. The Axiom SandPiper GPS engine will work by itself, as its NMEA serial outputs are RS232. The Jupiter GPS - NMEA outputs need to be converted from TTL to RS232 on its serial ports to talk with a standard computer serial port.
Most standard computer serial ports require RS232 level data for proper data transfer. But, due to the many variables in computer serial ports by many and various manufacturers, some computers just might work with TTL data levels. This is a hit or miss proposition and is not 100% reliable and could possibly cause damage to the inner workings you your computer. So this is not recommended.
At the present time, the DSP-10 software, only transfers data FROM the GPS engines to the computer and NO DATA is being sent from the computer TO the GPS engines. Thus, all GPS engine software setup must be done separately with software that is provided by your GPS engine seller or manufacturer.
PRINTED CIRCUIT BOARD
The printed circuit board is designed by W7CQ and I used the ExpressPCB Software for both the schematic and board layout. ExpressPCB Software is available for free from http://www.expresspcb.com/. This board is designed to fit ExpressPCB's Miniboard Service and as of June 2006, they cost $51.00 + shipping for three boards in a 2.8" by 3.5" format.. You might want to contact two other hams to share a common order of 3 boards. This makes the cost of each board about $20.
I have no plans to produce this board but in the sharing spirit of Ham Radio, I am releasing the design to ham radio operators to use and share on a non commercial basis.
RS232 Switch Manual (500kb) with Theory, Schematics, Parts List and Wiring Details in pdf format.
RS232 Schematic can be viewed and edited using the ExpressPCB software.
Printed Circuit Boards can be viewed and modified using the ExpressPCB software.
RS232 Parts List with suppliers and ordering information.
NOTE: The two ExpressPCB files can be linked together to use for error checking of modifications.
On the four position switch above, the AUX2 & AUX1 connectors are wired with short cables to solder pads provided on the PC board.
I wish to thank, Johan KC7WW, Mike KD7TS, Ernie W7LHL, and Bob W7PUA for all their ideas, suggestions, help and proofreading that helped this project come to its present state.
Jimmy W7CQ
***************** No Warranty *****************
Jimmy Oldaker W7CQ
27640 Gibraltar Loop
Eugene, Oregon 97405
541- 686- 8396
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Copyright 2006 - Jimmy Oldaker Last edited: 18 February 2008 05:42 PM |