motorVMC

A Virtual Motor Controller (VMC) with EPICS support.

Python scripts

The server behaves like a eight-axis motor controller. The default axis values are consistent with stepper motors in half-step mode (400 steps per rev). The axes can be addressed by name (X, Y, Z, T, U, V, R, S) or number (1, 2, 3, 4, 5, 6, 7, 8). The controller accepts values in units of counts. The server returns an "OK" string in response to non-query commands.

Starting the server

$ python3 server.py

This will start the server, which listens by default on port 31337. The port number can be changed by modifying DEFAULT_PORT in server.py.

Command reference

  Input terminator: \r\n
  Output terminator: \r

  Command syntax:
    <axis> <command> [argument]

  Commands:

  1 MV <position>		# Absolute move (counts)
  1 MR <displacement>		# Relative move (counts)
  1 JOG <velocity>		# Jog (counts/s, signed)
  1 POS <position>		# Set position (counts)
  1 ACC <acceleration>		# Set acceleration (counts/s/s)
  1 VEL <velocity>		# Set velocity (counts/s)
  1 BAS <base_velocity>		# Set base velocity (counts/s)
  1 AB				# Abort motion
  1 POS?			# Query position (returns: counts)
  1 ST?				# Query status (returns: integer)
	 Status bit definitions:
	 Direction	0x1
	 Done moving	0x2
	 Moving		0x4
	 High limit	0x8
	 Low limit	0x10
	 Homing		0x20
	 Home limit	0x40
	 Homed		0x80
	 Error		0x100

  1 ACC?			# Query accel (returns: counts/s/s)
  1 VEL?			# Query velocity (returns: counts/s)
  1 LL <position>		# Set low limit (counts)
  1 HL <position>		# Set high limit (counts)
  1 LL?				# Query low limit (returns: counts)
  1 HL?				# Query high limit (returns: counts)

EPICS support

Prerequisites

• EPICS base
• asyn
• motor

Configuration

• The definitions of MOTOR and EPICS_BASE need to be corrected in motorVMC/configure/RELEASE before motorVMC can be built.
• [optional] The PREFIX and VMC_PORT environment variables can be customized. VMC_PORT needs to match the DEFAULT_PORT used by server.py

Building motorVMC

$ cd motorVMC
$ make

Run the example IOC

$ cd motorVMC/iocs/vmcIOC/iocBoot
$ ../../bin/${EPICS_HOST_ARCH}/vmc st.cmd