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Configuration / Mount

In order to customize OnStepX behavior to each users requirements there are a variety of configuration settings in the Config.h file.

Many settings are optional but those settings that must always match your hardware and must be set properly are highlighted in red. In some cases that's enough to get a working telescope controller but usually you also have to fill in the stepper driver information also, at a minimum, which is highlighted in yellow. In all cases you should only change the Value column of the Config.h file to the required selection.

Also, while working on your Config.h file take note of the "Hint" column to the far right, it's there to assist you in determining which settings are critical and which can most often be ignored.

There are numerous checks performed at compile time: Read the compiler warnings and errors, they are there to help guard against invalid configurations.

The Config.h file settings are categorized as follows:

MOUNT TYPE

Set this to match your mount type. The default Meridian Limits in GEM (German Equatorial Mount) mode are 15 degrees past the Meridian on the East or West side before the mount flips. The Meridian Limit defaults can be changed using run-time settings. In ALTAZM (Dobsonians etc.) mode Meridian Limits are disabled allowing a full range of motion but in a single orientation without Meridian Flips.

In spite of its name the GEM mount type can be used with Fork, Yoke, and other types (but not ALTAZM) as well depending on how you configure the Limits and use the Preferred Pier Side feature. The GEM option can even allow a full 360° range of motion on either side of the Meridian should that be required for unobstructed and other more exotic designs.

Parameter Name

MOUNT_TYPE
- Default Value: GEM
- Other Values: ALTAZM, ALTAZM_UNL, GEM, GEM_TA, GEM_TAC, FORK, FORK_TA, FORK_TAC
- Notes:
  - For ALTAZM mounts (Dobsonians, etc.) the default home position is at 0 degrees Azimuth (North) and 0 degrees Altitude (on the Horizon.)
    - Suffix _UNL allows unlimited motion about the Azimuth axis (AXIS1_LIMIT_MIN and _MAX are ignored.)
    - Meridian flips, or in this case the ability to enter the alternate orientation, is disabled.
  - For GEM (German Equatorial Mount) and FORK mounts the default home position is always pointing at the NCP (North Celestial Pole) or SCP (South Celestial Pole) depending on the site Latitude being in the northern or southern hemisphere. The RA axis hour angle is 6 hours for GEM mounts and 0 hours (on the Meridian) for FORK mode mounts. Additionally, FORK mode disables the Meridian limits.
    - Suffix _TA and _TAC enables tangent arm support for mounts where the Declination axis has a very limited range of movement, often allowing for only ~ +/- 5 or 10 degrees.
      - The common [Reset Home] control in OnStep applications sets the center of the TA travel.
      - The common [Find Home] control in OnStep applications moves (only) the TA back to center.
      - You can then press [Find Home] just before manually moving to a bright star near a new target.
      - Once there press [Sync] and you are free to do gotos within the limits of the TA travel... or if you have encoders this Sync is done automatically as you move and as soon as you stop anywhere near the target you can do the goto.
      - Goto and guide movement exceeding the TA travel (limits) is not allowed.
        
        Software defined limits AXIS2_LIMIT_MIN and AXIS2_LIMIT_MAX constrain the TA (Tangent Arm) travel, when setting these limits be sure to allow for a little extra distance to let fast guided motion stop once the limit is broken. To keep this distance short don't allow fast slews (a low SLEW_RATE_BASE_DESIRED) and keep the acceleration distances short and set to the same value (SLEW_ACCELERATION_DIST and SLEW_RAPID_STOP_DIST.)
        
        Hardware defined limits using AXIS2_SENSE_MIN and AXIS2_SENSE_MAX and a home switch AXIS2_SENSE_HOME are also supported.
        
        Any home switch setup only applies to Axis2 and [Find Home] works as described except the home switch determines the TA center location.
      - _TA has no geometry correction applied so this is appropriate for drives that don't vary in ratio across the range of motion (a sector gear worm drive for instance.)
      - _TAC has tan() geometry correction applied (by default.) The tangent arm correction can be changed to something other than the defaults by adding the following lines (with new formula) to Config.h:
        
        #define TANGENT_ARM_INSTRUMENT_TO_MOUNT(a) (atan(a)) // returns angle in radians
        
        #define TANGENT_ARM_MOUNT_TO_INSTRUMENT(a) (tan(a)) // angle (a) in radians
        
        The default geometry correction assumes that at the center of the TA mechanism the arm length is shorter than at the ends. Like a "T" where the vertical arm sweeps left/right of center traveling on a screw. At the center the arm length is less and so the reduction ratio is less, toward either end the ratio becomes higher and this option compensates for the effect.
- Reminder:
  - The home position can be changed to something other than the defaults by adding the following lines to Config.h with the angular positions you need:
    - #define AXIS1_HOME_DEFAULT 0 // angle in degrees, for the RA or Azimuth Axis.
    - #define AXIS2_HOME_DEFAULT 20 // angle in degrees, for the Dec or Altitude Axis.

TIME AND LOCATION

A time location source can provide the Date/Time and optionally the Latitude/Longitude to OnStep. Only the GPS option is capable of providing both Date/Time and Latitude/Longitude, all others provide only the Date/Time.

TIME_LOCATION_SOURCE
- Default Value: OFF
- Other Values: OFF, DS3231, DS3234, TEENSY, GPS, NTP
- Notes:
  - The DS3231 uses the OnStepX default I2C bus on the microcontroller.
    - This is an I2C device and so it has an address (0x68) which is used to identify it on the I2C bus.
    - We often use a "ZS042" module which is really two devices in one, as it also contains an AT24C32 I2C EEPROM at address (0x57.)
      - This EEPROM is sometimes required (depending on the board) for OnStepX to operate.
      - If this EEPROM is required and not found an initialization error will occur and OnStepX will flash an error code on the Status LED (1 flash per cycle) at startup.
  - The DS3234 uses the default SPI bus (see your pin-map to locate CS etc.) on the microcontroller.
  - The TEENSY option uses the on-board Teensy3.2 RTC hardware (which requires adding a crystal and battery.)
  - The GPS module needs to be attached to a hardware serial port (see below.)
  - The NTP option needs additional #define lines in Config.h (see below.)
- Associated Options:
  - Adding a GPS to OnStepX requires specifying an otherwise unused hardware serial port for GPS.
    - For example you might use Serial6 by adding the following line to Config.h:
      - #define SERIAL_GPS Serial6
    - Or a software serial port (which can be on "any" pins) by adding the following lines to Config.h:
      - #define SERIAL_GPS SoftSerial
      - #define SERIAL_GPS_RX 12
      - #define SERIAL_GPS_TX 11
        
        Note: the capabilities of a software serial port depends on the platform specific library used. Some can't receive data on arbitrary pins (Teensy) etc. so your results may vary. Some don't need a TX pin specified at all (which is fine as this doesn't use TX for anything) and using -1 as the pin seems to do the trick.
    - The default baud rate for this port is 4800, but that can be overridden with something similar this in Config.h:
      - #define SERIAL_GPS_BAUD 9600
  - The NTP option requires using SERIAL_IP_MODE STATION (on an ESP32) and adding the NTP server IP address to Config.h
    - For example using :
      - #define TIME_IP_ADDR {129,6,15,28} // time-a-g.nist.gov
    - Network configuration is also required (Google if you don't know how) and add similar to the following to Config.h as required for your LAN:
      - #define STA_DHCP_ENABLED false      // true to use LAN DHCP addresses
        #define STA_IP_ADDR {192,168,0,2}   // Wifi Station IP Address
        #define STA_GW_ADDR {192,168,0,1}   // Wifi Station GATEWAY Address
        #define STA_SN_MASK {255,255,255,0} // Wifi Station SUBNET Mask
- Reminder:
  - Sometimes a TLS can also provide an high accuracy PPS (Pulse Per Second, see the section below.)
  - If the specified device is not detected OnStepX will flash an error code on the Status LED (5 flashes per cycle) at startup.
TIME_LOCATION_PPS_SENSE
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Senses signal rising edge. A high accuracy PPS (Pulse Per Second) reference helps OnStep improve tracking accuracy. This is especially important for some Arduino Mega2560 boards where the microcontroller oscillator uses a low accuracy Ceramic Resonator as opposed to a much higher accuracy Crystal. Most of our custom PCB designs accommodate the DS3231 RTC and have the PPS signal along with power and I2C connections on the header for it.
- Reminder:
  - For many PCB designs this input does NOT have a pullup resistor but the microcontrollers internal pullup is automatically activated if available.

STATUS

These options provide status feedback as to what the OnStepX Mount is doing.

Parameter Name

STATUS_MOUNT_LED
- Default Value: ON
- Other Values: OFF, ON
- Notes:
  - If ON the Mount status LED becomes active when tracking is first started and may use the same PIN as the controller STATUS_LED (which then becomes disabled.)
  - Illuminates continuously when the mount is slewing.
  - Flashes proportional to the tracking/guiding rate when operating at low speeds where the flash rate based on the fastest rate of Axis1 and Axis2. Some examples follow:
    - At normal 1x sidereal tracking the led flashes twice a second.
    - When guiding at 0.5x to the East the LED flashes once a second.
    - When guiding at 0.5x to the West the LED flashes three times a second.
    - When guiding at 2.0x to the North the LED flashes four times a second.
STATUS_BUZZER
- Default Value: OFF
- Other Values: OFF, ON, 100 to 6000 (Hz freq.)
- Notes:
  - Use ON where a piezo buzzer makes sound whenever power is applied or set the frequency in Hz where an attached speaker needs an oscillating signal to make sound.
  - The buzzer becomes active when tracking is first started and may use the same PIN as the controller STATUS_LED (which then becomes disabled.)
    - Having the Mount status LED and buzzer on the same pin works best when using a speaker (not piezo buzzer.)
- Associated Options:
  - STATUS_BUZZER_DEFAULT ON to enable alert sounds at boot or OFF to disable; you can also enable/disable the buzzer at run-time.
  - STATUS_BUZZER_MEMORY ON to remember whatever the last runtime setting was across power cycles.

ST4 INTERFACE

It is up to you to verify the interface meets the electrical specifications of any connected device, use at your own risk.

ST4_INTERFACE
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Operation is limited to <= 1x guide rates unless hand control mode is used.
- Associated Options:ST4_HAND_CONTROL
  - Default Value: OFF
  - Other Values: ON, OFF
  - Notes: Enable for Basic Hand Control (just N,S,E,W buttons) special features and SHC support.
    - After 4 seconds of inactivity the HC will return to normal operation.
    - If a BUZZER is available there will be a beep going into/out-of the Alternate Modes and a click with each button press.
    - Hold [E] + [W] buttons for > 2 seconds for Alternate Mode A:
      - The [E] and [W] buttons adjust the Guide Rate slower or faster.
      - The [N] button turns tracking on and off.
      - The [S] button causes a Sync to occur (or accepts Align.)
    - Hold [N] + [S] buttons for > 2 seconds for Alternate Mode B:
      - The [E] and [W] buttons select objects in the current User Catalog.
      - The [N] button does a Goto to the currently selected object.
      - The [S] button turns sound on/off.
  - Associated Options:ST4_HAND_CONTROL_FOCUSER
    - Default Value: OFF
    - Other Values: OFF, ON
    - Notes: Basic Hand Control focuser in Alternate Mode B:
      - Hold [N] + [S] buttons for > 2 seconds for Alternate Mode B:
        
        The [E] button selects Focuser1.
        
        The [W] button selects Focuser2.
        
        The [N] button moves the current focuser in.
        
        The [S] button moves the current focuser out.
- Reminder:
  - Often PCB designs have pullup resistors on these signal pins, however the microcontrollers builtin pullup resistors are also enabled if available.
  - Often PCB designs also have an optional shunt to make +5VDC available on pin 1 of the RJ12 modular connector which is required if using an SHC on the ST4 port.
  - The de-bounce noise filter on ST4 port pins is 5ms unless hand control mode is ON in which case it is 100ms (affects responsiveness.)

GUIDING BEHAVIOR

GUIDE_TIME_LIMIT
- Default Value: 10
- Other Values: 0 to 120 (Seconds)
- Notes: Time limit for guide operations.
- Reminder:
  - Due to the LX200 command design a communication fault can lead to a guide that never stops, this guards against that.
GUIDE_DISABLE_BACKLASH
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Enable this to disable backlash when guiding at <= 1X rate (as used for auto-guiding/pulse-guide.)

LIMITS

LIMIT_SENSE
- Default Value: OFF
- Other Values: OFF, HIGH, LOW, etc.
- Notes:
  - Limit sense switches can be wired in parallel (for NO normally open) or series (for NC normally closed) so several can be used where any switching event causes OnStep to stop tracking and slews (allowing for SLEW_RAPID_STOP_DIST.) This is most often implemented as a panic switch the user can press and/or lever switches on the mount axes.
  - Normally one would use switches that close with a contact to ground then, HIGH for NO (normally open) and LOW for NC (normally closed) switches.
  - This parameter is a "stand-in" for more elaborate functionality in OnStepX since Axis1 and Axis2 each have a minimum limit sense and a maximum limit sense. So, the Mount in OnStepX has up to four limit sense inputs. If specified here all four limit sense inputs are associated with a single pin in the pinmap (similar to how earlier versions of OnStep worked.)
- Reminder:
  - Often PCB designs have a fairly strong pullup resistor along with a bypass capacitor to provide basic ESD protection on this input.
  - By default the microcontrollers builtin pullup resistor (if supported) is enabled so the pin is normally in the OFF state if LOW is used. This can be overridden with the corresponding AXISn_SENSE_LIMIT_INIT setting (see Config.defaults.h)
LIMIT_STRICT
- Default Value: OFF
- Other Values: OFF, ON
- Notes:
  - If ON limits enabled at startup.
  - If OFF limits are disabled until the date/time is set and a Goto, or Sync, or UnPark is done.
- Reminder:
  - Disabling this (OFF) is useful for mounts without clutches where you want the freedom to guide to reach the home position without OnStep possibly stopping you its best.
  - Enabling this (ON) results in the mount being unable to move until the date/time is set.
  - OnStep assumes the user has the correct Latitude and Longitude set.
  - The date/time can be automatically set at boot from a RTC (or GPS) module or later by controlling applications.

PARKING BEHAVIOR

PARK_SENSE
- Default Value: OFF
- Other Values: OFF, HIGH, LOW, etc.
- Notes:
  - A park sense switch (or switches) can be wired in so a switch closure provides OnStepX with confirmation that the park position has been arrived at.
- Reminder:
  - Often PCB designs have a fairly strong pullup resistor along with a bypass capacitor to provide basic ESD protection on this input.
  - By default the microcontrollers builtin pullup resistor (if supported) is enabled so the pin is normally in the OFF state if LOW is used. This can be overridden with the corresponding PARK_SENSE_INIT setting (see Config.defaults.h)
  - Most pinmaps don't have an entry for this, so you would normally have to add #define PARK_SENSE_PIN with the microcontrollers pin#.
PARK_SIGNAL
- Default Value: OFF
- Other Values: OFF, HIGH, LOW, etc.
- Notes:
  - Input signal that responds to the specified state to trigger parking the mount (if possible.)
- Reminder:
  - Most pinmaps don't have an entry for this, so you would normally have to add #define PARK_SIGNAL_PIN with the microcontrollers pin#.
PARK_STATUS
- Default Value: OFF
- Other Values: OFF, HIGH, LOW
- Notes:
  - Outputs the specified signal state when the mount is successfully parked (or the opposite state otherwise.)
- Reminder:
  - Most pinmaps don't have an entry for this so you would normally have to add #define PARK_STATUS_PIN with the microcontrollers pin#.

PARK_STRICT
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Un-parking is only allowed if successfully parked.
- Reminder: Normally Un-parking is allowed even if not Parked when at the Home Position. This is a recovery feature that allows you to manually re-orientate the mount to near the park position then Un-park to restore operation (including the pointing model) should you loose control due to a power outage, etc.

PEC

PEC_STEPS_PER_WORM_ROTATION
- Default Value: 0
- Other Values: 0 to disable PEC, 77 to 862920 (in steps)
- Notes:
  - This is the number of steps needed to cause the worm of a worm/wheel gear (or other final reduction stage) to rotate once.
- Reminder:
- - Ignored in ALTAZM mode.
PEC_SENSE
- Default Value: OFF
- Other Values: OFF, HIGH, LOW, etc.
- Notes:
  - PEC (Periodic Error Correction) Index sense via digital OR analog threshold.
  - This provides for automatic recovery of the PEC Index without using OnStepX's Park functionality.
  - When HIGH the PEC index sense event is triggered by the signal going from a 0V to 3.3V (or Vcc.)
  - When LOW the PEC index sense event is triggered by the signal going from a 3.3V (or Vcc) to 0V.
  - Once an sense event has occurred, additional sense events are ignored for 60 seconds to block spurious signals near the trigger threshold.
- Reminder:
  - Ignored in ALTAZM mode.
  - For most PCB designs this input doesn't have a pull-up resistor but does have a bypass capacitor (or TVS device) to provide basic ESD protection.
  - By default the microcontrollers builtin pullup resistor (if supported) is enabled so the pin is normally in the OFF state if LOW is used. This can be overridden with the corresponding PEC_SENSE_INIT setting (see Config.defaults.h)
PEC_BUFFER_SIZE_LIMIT
- Default Value: 720
- Other Values: 0 to 30000 (seconds)
- Notes:
  - Maximum size of the PEC buffer storage area.
  - Also requires NV (EEPROM, etc.) storage of sufficient size to hold the buffer contents and other settings.

TRACKING BEHAVIOR

TRACK_BACKLASH_RATE
- Default Value: 20
- Other Values: 2 to 50 (x sidereal rate)
- Notes: Backlash take up rate. Too fast and motors stall/gears slam as they run into the load of stationary telescope/mount at high speed. Too slow and mount becomes less responsive.
- Reminder: The amount of backlash for the mount axes is configured at run-time.
TRACK_AUTOSTART
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Start with tracking enabled.
- Reminder:
  - Not supported for ALTAZM mounts.
  - If you have a TLS (Time Location Source) OnStepX will start normally.
    - It is up to you to make sure the site information (Latitude/Longitude) is always correct if using this option.
    - If parked, the mount will automatically unpark.
    - With GPS normal mount operation starts when a lock occurs.
  - If you do not have a TLS the mount will start tracking with limits disabled.
  - Good for testing but generally I do not recommend using this option.
TRACK_COMPENSATION_DEFAULT
- Default Value: OFF
- Other Values: OFF, REFRACTION, REFRACTION_DUAL, MODEL, MODEL_DUAL
- Notes: Start with just refraction or refraction/pointing model compensated tracking enabled. Single or dual axis.
- Reminder: These tracking options can also be selected at runtime.
TRACK_COMPENSATION_MEMORY
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Select ON to remember the last selected tracking rate compensation setting across power cycles.

SLEWING BEHAVIOR

SLEW_RATE_BASE_DESIRED
- Default Value: 1.0
- Recommended Values: 0.4 to 10 (degrees per second)
- Notes: Desired slew rate in degrees/second and adjustable at run-time from 1/2 to 2x the nominal rate.
- Reminder:
  - This is the desired slew rate which OnStepX may slow down to meet microcontroller performance limitations to arrive at the nominal rate.
  - Other settings can affect performance limits, those include the overall AXISn_STEPS_PER_DEGREE, STEP_WAVE_FORM, AXISn_DRIVER_MICROSTEPS_GOTO, and related options.
SLEW_RATE_MEMORY
- Default Value: ON
- Other Values: OFF, ON
- Notes: Remembers slew rates, set in the 1/2x to 2x nominal slew rate range at run-time, across power cycles.
SLEW_ACCELERATION_DIST
- Default Value: 5.0
- Recommended Values: 0.1 to 20 (degrees)
- Notes: Approx. distance for acceleration (and deceleration.)
SLEW_RAPID_STOP_DIST
- Default Value: 1.0
- Recommended Values: 0.1 to 10 (degrees)
- Notes: Approx. distance required to stop when a slew is aborted or a limit is exceeded.
GOTO_FEATURE
- Default Value: ON
- Recommended Values: ON, OFF
- Notes: Option to disable the goto functionality.
- Reminder:
  - When OFF motion is limited to <= 20x sidereal and goto commands trigger a sync instead with the intention that the user will be pushing the mount to that target.
GOTO_OFFSET
- Default Value: 0.25
- Recommended Values: 0.0 to 2.0 (degrees)
- Notes:
  - Offset is degrees for goto unidirectional approach.
  - When enabled a goto is first done to the south/east of the target (target east of the pier) or to the north/east of the target (target west of the pier) by the specified amount.
  - Then, normally, a second goto is then done to always arrive at the target from the same relative direction.
- Reminder:
  - This feature is automatically disabled for ALTAZM mounts.
GOTO_OFFSET_ALIGN
- Default Value: OFF
- Recommended Values: ON, OFF
- Notes:
  - When enabled and in align mode no additional goto is done and instead the user is responsible for guiding to center the target. This is best done using just the north/west guide controls (if east of the Pier) or the south/west controls (if west of the Pier.)
    - This functionality improves the accuracy of alignment and goto operations if followed.

PIER SIDE BEHAVIOR

MFLIP_SKIP_HOME
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Default OFF causes gotos to slew to the home position first when a meridian flip is required. This helps prevent cords from becoming tangled or snagged in some cases.
- Reminder:
  - For GEM mode only.
  - Enable and gotos slew directly to the destination without visiting home position, even if a meridian flip is required.
MFLIP_PAUSE_HOME_MEMORY
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Remember meridian flip pause at home setting across power cycles.
- Reminder:
  - For equatorial mounts only.
  - Meridian flip pause at home causes OnStepX to wait at the home position for confirmation before continuing on to the destination when a meridian flip is required.
MFLIP_AUTOMATIC_MEMORY
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Remember automatic meridian flip setting across power cycles.
- Reminder:
  - For equatorial mounts only.
  - If enabled this automatic meridian flip setting causes a goto with meridian flip to occur when the mount tracks into the meridian limit when west of the pier.
PIER_SIDE_SYNC_CHANGE_SIDES
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Enable to allow syncs to change the pier side.
- Reminder:
  - For equatorial mounts only.
  - If enabled be careful to recognize when a sync changes pier sides and manually reorientate the mount if required.
PIER_SIDE_PREFERRED_DEFAULT
- Default Value: BEST
- Other Values: EAST, WEST, BEST
- Notes:
  - Default BEST is good for visual work as gotos won't cause a Meridian Flip unless necessary to reach the target.
  - The EAST setting is good for imaging w/ SGP and N.I.N.A. as it interoperates better with their automatic meridian flip capabilities.
  - The WEST setting is rarely used but can be handy to force the west pier side during syncs and gotos.
- Reminder:
  - For equatorial mounts only.
PIER_SIDE_SYNC_CHANGES_SIDES
- Default Value: OFF
- Other Values: OFF, ON
- Notes:
  - Enables ability of a sync. to change pier sides.
  - Normally OFF to avoid problems with users being unaware of an expected change in orientation.
- Reminder:
  - For equatorial mounts only.
  - A sync. can cause much confusion if the mount isn't manually moved into the alternate orientation as required to match the pier side change.
  - Many control applications provide side of pier information, some like my Sky Planetarium will warn you if a sync. causes a pier side change.
PIER_SIDE_PREFERRED_MEMORY
- Default Value: OFF
- Other Values: OFF, ON
- Notes: Remember preferred pier side setting across power cycles.
- Reminder:
  - For equatorial mounts only.