One Mile Radio Telescope
Operational Interface "OI" command set

Version 1.02 April 2000

Overview

This has a simple set of 3 commands and one common response.

Ethos

The hardware interface has no state - other than retaining the parameters of the OI command. This avoids any mis-synchronisation between "DOS Console" application and the interface. "Permanent" state is held in the Non Volatile Ram for safety limit checking. 

There will be no intelligence to anticipate motor run on. This is the responsibility of the "DOS Console" application.

Commands

"OI" Parameters are passed to the hardware interface  
"EH" (Enquire Heading) a passive command that will cause the hardware interface to respond
"NV" (Non Volatile) Sets the non volatile memory. (Valid range of encoder destinations. This command is only carried out if test switch 1 is on.)

Command Format

OI <HA speed><HA dir><HA track><HA dest><DEC speed><DEC dir><DEC dest>

EH

NV <HA Limit 1><HA Limit 2><DEC Limit 1><DEC Limit 2>

All commands are terminated by an ASCII <CR>.

Common Response

Always sent after a command

ST<valid command><Limit switches><HA control><HA encoder><DEC Control><DEC encoder>

Protocol

Any attempt to send a new command whilst a response is being received is not allowed, and will be ignored. This is to prevent commands being queued up, and responses being misinterpreted for previous commands.

RS232 is used - "8 none and 1" at 9600 baud

OI Command Format

field Description Syntax
1 HA Speed Park
Slow
Fast
2 HA Dir + (Move HA < param)
- (Move HA > param)
May be clear if HA speed is set to Park
3 HA Track No track)
Track)
4 HA Dest unsigned 16 bit encoder Hour Angle
5 DEC Speed Brake
Release
Slow
Fast
6 DEC Dir + (Move DEC < param)
- (Move DEC > param)
May be clear if DEC speed is set to Brake
7 DEC Dest unsigned 16 bit encoder Declination

Example:

Sending:
OI,S,-,N,3456,B,,0000

would instruct the dish to move the HA axis slowly while the encoder reads greater than 3456. DEC Brake is on, No sidereal tracking.

Note we work in 16 bit encoder units: we don't know about base 60, or base 24!

All fields are in ASCII comma separated variable format.

Numeric fields may have 0 or more characters. e.g. the above example could be typed in on a VDU:

OI,S,-,N,000003456,B,,

... and would mean the same.

From Interface to PC - the Common Response

bit\field 1 2 3 4 5 6
7   Limit switch 7 Interface OK unsigned
16 bit
encoder 

Hour Angle encoder
current
reading

   unsigned
16 bit
encoder

Declination encoder
current
reading
6   Limit switch 6    
5   Limit switch 5    
4   Limit switch 4 Tracking
motor
running		 Dec Brake is off
3   Limit switch 3 HA motor running Eastward Dec motor running Southward
2 DEC
Destination error		 Limit switch 2 HA motor running  Westward Dec motor running  Northward
1 HA
Destination error		 Limit switch 1 HA motor running fast Dec motor running fast
0 Command OK Limit switch 0 HA motor running slow Dec motor running slow

This reports back to the PC.

For the above command example we will get this response:

ST,1,00,85,36f0,0,0

The "DOS Console" applications sends

EH

..and we get

ST,1,00,85,3558,0,0

.. and we continue...

EH
ST,1,00,85,3458,0,0
EH
ST,1,00,80,3654,0,0
EH
ST,1,00,80,3658,0,0

The "Interface OK" bit reports that interface has a problem or is operating OK.

This could be due to Illegal command, safety shut down.

Limit switches

0 HA extreme -
1 HA safe -
2 HA safe +
3 HA extreme +
4 Dec extreme -
5 Dec safe -
6 Dec safe +
7 Dec extreme +

Play with the scope drive emulation here.

History

1.02 26/4/2000 Common Response Field 3 bit 4 added. We now report the tracking motor running state.