motorDSM is a submodule of [motor](https://github.com/epics-modules/motor). When motorDSM is built in the ``motor/modules`` directory, no manual configuration is needed.
motorDSM can also be built outside of motor by copying it's ``configure/EXAMPLE_RELEASE.local`` file to ``RELEASE.local`` and defining the paths to ``EPICS_BASE``, ``MOTOR``, and itself.
motorDSM contains an example IOC that is built if ``configure/CONFIG_SITE.local`` sets ``BUILD_IOCS = YES``. The example IOC can be built outside of the driver module. Copy ``iocs/dsmIOC/configure/EXAMPLE_RELEASE.local`` to ``RELEASE.local`` and uncomment and set the paths for the appropriate lines depending on whether motorDSM was built inside the motor module or independently.
In ``motorDSM/iocs/dsmIOC/configure``, copy ``EXAMPLE_RELEASE.local`` to ``RELEASE.local``. Comment out the "if built inside motor" lines, uncomment the "if built outside motor" lines, and set the path for ``MOTOR_DSM``.
where `[controller name]` is the name of the motor to assign. Convention is to use "MD90n", starting with n=0.
**5. Intialize the IOC**
After the call to `iocInit` (still in the st.cmd.md90[.multiple] file), issue the following commands for each motor. The example below uses `DSM:m0` but it should be run for each line described in motor.substitutions.md90 (or motor.substitutions.md90.multiple).
````
dbpf("DSM:m0.RTRY", "0") #sets retries to 0; this is automatic on the MD90
dbpf("DSM:m0.TWV", "0.1") #Tweak distance
dbpf("DSM:m0.VMAX", "1.0") #Sets max velocity to 1 mm/s
dbpf("DSM:m0.HVEL", "1.0") #Sets max velocity to 1 mm/s
````
**6. Update the substitutions file**
Save and close the st.cmd file you've been configuring, then open the motor substitutions file (motor.substitutions.md90[.multiple]).
Ensure the values in the `pattern` block's `PORT` field match the names used in the std.cmd file.
Note that, despite this field being called "Port", they use the names of the MD90 Controller object defined above (by default, MD900, MD901, etc.
Do __not__ use the direct serial port names (by default, serial0, serial1, etc.).
This reads the REP variable, which is the "Raw Encoder Position". Additionally, change `m0` to `m1`, `m2`, etc. to read the values from other motors when running more than one.
(Note that velocity targets are appropriate only. They adjust the step rate of the motor and are not guaranteed to be exact.)
A note aboue velocity targets
-----------------------------
The I-20 motor driven by the MD-90 is a closed loop "step and repeat" motor that takes full steps towards its position target until it is
close, then will perform linear extensions to close the loop on the target position. This is handled internally on the MD-90, not by
EPICS.
The Velocity target parameter sets the step frequency
at which the motor operates on its way to the target position. The speed is not closed loop, and will depend on external loads, environmental
conditions, etc. A speed target of 1 mm/s will generate a roughly 1 mm/s motion, but it is not guaranteed.
Additionally, due to the way EPICS operates, setting VELO will not immediately send a command to the MD90. Instead, EPICS remembers the last value you set, and will set this new
velocity target when it sends the next move command. **However, the motor must not be in servo mode to accept a new velocity target.**
The motor enters servo mode when you send a new position target, and stays in servo mode until you issue a Stop command
(by setting the `DSM:m0.STOP` parameter to 1).
If you do not disable servo prior to issuing a Move command at the new velocity, then VELO will become out of sync with the actual motor
velocity, and EPICS will return error 3 "Cannot execute while moving" in its console each time you issue a Move command.
This is because each Move command internally sends a "Set step frequenc" command, which will error if you do not Stop the motor first.
Reading the VELO parameter at this point will return the wrong value- it returns the value you requested, not the actual speed setting
on the motor.
To fix this, you must Stop the motor, then send a new Move command. At
