Hardware Controllers Manual

Introduction

These controllers move telescope axes, process guide images, adjust mirrors, operate devices in the enclosure, and control the mirror covers and such. Each controller accepts text commands via a standard RS-232 serial interface. In addition, some controllers require a separate highly accurate 1 Hz reference pulse.

Multiple controllers (except the guide image controller) may co-exist in one box and share one serial interface. Specify which controller before sending a command. Prefix the command with a device specifier word. For example, ROT STATUS solicits status from the rotator controller.

Standard Interface

Each hardware controller uses the following standard interface. It is based on FORTH controllers, since those are widely used. It was designed to be simple and easy to implement. Some of these rules only apply to commands that the TCC may execute, and so may be relaxed for engineering commands. "Commands" and "input" refer to data input to the controller. "Replies" and "output" refer to data output by the controller.

• Commands and replies are plain, readable ASCII text.
• Commands are terminated with <cr> (carriage return).
• Commands must be echoed.
  • The command echo should be in the same case as the received command. If it helps, the TCC can be expected to supply commands in the appropriate case to make this so. However, it would be best not to rely on this.
  • Data and error messages may not appear on the same line as the command echo, but instead must start on a new line. Otherwise the TCC will think that the command was garbled.
• Unsolicited output is prohibited except after the controller is reset or restarted, or after catastrophic failure requiring reset. The TCC may ignore unsolicited output or it may try to initialize or reset the controllers; the TCC's behavior is unpredictable. Do not use unsolicited output as an attempt to get the TCC's attention.
• Each line of output must be terminated with a carriage return. A linefeed may also be supplied, but will be ignored by the TCC. If supplied, the linefeed may be sent just before or just after the <cr>, but "before" is preferred because it is less likely to cause mysterious symptoms in case of trouble.
• The last line of output in response to a command must be terminated with "OK" and the termination mentioned above.
  • This OK may be appended to the last line of output (in which case it must be preceded by at least one space) or it may appear by itself on a new line. Case is irrelevant.
  • Exception: a blank command (zero or more spaces followed by a carriage return) must receive just one line of reply, consisting of zero or more spaces followed by OK.
• Parameters are separated by one or more spaces. This is a strong recommendation but not a requirement.

Note: The Galil motion controllers output a semicolon for each command that appears on a line (as part of the command echo). As a result, the TCC's standard interface driver was enhanced to allow ignoring one specific character in replies. When talking to the Galils the TCC ignores semicolons in replies.

Russell Owen