Theia Technologies offers a MCR600 motor control board for controlling Theia's motorized lenses. This board controls focus, zoom, iris, and IRC filter motors. It can be connected to a host comptuer by USB, UART, or I2C connection.

The MCR600 board (and MCR400, MCR500 and others in the MCR series) has a proprietary command protocol to control and get information from the board. The protocol is a customized string of up to 12 bytes which can be deciphered in the MCR600 documentation. For ease of use, Theia has developed this Python module to format the custom byte strings and send them to the board. For example, the user can request the focus motor to move 1000 steps. The focusRel() function will convert this request to the appropriate byte string and send it over USB connection to the MCR control board. This will cause the lens motor to move 1000 steps.

This module can be loaded into a Python program using pip.
pip install TheiaMCR
Theia's motorized lens should be connected to the MCR600 board and the board should be connected to the host computer via USB connection thorugh a virtual com port. The class must be initizlized first using the __init__() function.

# create the motor control board instance
MCR = mcr.MCRControl(comport)

Then the motors must all be initialized with their steps and limit positions.

# initialize the motors (Theia TL1250P N6 lens in this case)
MCR.focusInit(8390, 7959)
MCR.zoomInit(3227, 3119)
MCR.irisInit(75)
MCR.IRCInit()

The initialization commands will create instances of the motor class for each motor which can be accessed by focus, zoom, and iris named instances. If the MCRControl class was not successful (possibly due to hardware connection issue) any subsequent functions will return an error value. There are some board query commands that use the MCRBoard subclass. This subclass was automatically initilized.

Now the motors can be controlled individually. For example, the focus motor can be moved to an absolute step number.

# move the focus motor
MCR.focus.moveAbs(6000)
log.info(f'Focus step {MCR.focus.currentStep}')

For the internal IRC switchable filter, the state can be 1 or 2 to match the specification sheet. Usually filter 1 is visible only transmission and filter 2 is visible + IR transmission.

When ending the program, call MCR.close() to close the serial port and release any resources being used.

The parameters for focusInit(), zoomInit(), and irisInit can be found in the lens specification. These are the parameters for some of Theia's lenses.

• TL1250 (-N) lens:
  • focusInit(8390, 7959)
  • zoomInit(3227, 3119)
  • irisInit(75)
• TL410 (-R) lens:
  • focusInit(9353, 8652)
  • zoomInit(4073, 154)
  • irisInit(75) (updated v.2.5.0)

Each motor has these variables available

• motor.currentStep: current motor step number
• motor.currentSpeed: current motor speed in pulses per second (pps)
• motor.maxSteps: maximum number of steps for the full range of movement
• motor.PIStep: photointerrupber limit switch step position (within the full range of movement). After sending the motor to home, the current step will be set to this PIStep number.

More information about the available functions can be found in the wiki pages.

There are logging commands in the module using Python's logging libray. These are set by default to log WARNING and higher levels. To see other log prints in the console, initialize the class with MCR = TheiaMCR.MCRControl(serial_port="com4", degubLog=True) or manually set the logging level with TheiaMCR.log.setLevel(logging.INFO).
The module creates 2 rotating log files in the background by default based on Python's logging module. If the logging module isn't used, the log files can be disabled by calling MCR = TheiaMCR.MCRControl(serial_port="com4", logFiles=False).

Unhandled exceptions are logged to the log file using the sys.excepthook variable. This is a global variable so check the operation within your application if you set this variable elsewhere.

Theia Technologies BSD license Copyright 2023-2025 Theia Technologies

For more information contact: Mark Peterson at Theia Technologies mpeterson@theiatech.com

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