5.6. Homing

This section documents the details of the Tic’s homing procedure. For information about setting up limit switches and homing, see Section 4.14.

The homing procedure can be started using the “Go home” command documented in Section 6 or the automatic homing feature described in Section 6. When you start the homing procedure, you must specify a direction: forward or reverse.

The homing procedure performed by the Tic consists of the following steps:

  1. Set the “Position uncertain” flag.
  2. Set the target velocity in order to move the stepper motor towards a limit switch. The sign of the velocity is determined by the specified homing direction: forward homing corresponds to a positive velocity and reverse homing corresponds to a negative velocity. The magnitude of the velocity is specified by the “Homing speed towards” setting.
  3. Wait until a limit switch corresponding to the homing direction is active. For forward homing, this means that the Tic waits for a forward limit switch to be active. For reverse homing, the Tic waits for a reverse limit switch to be active. If you have not configured or wired your limit switches properly, this step might run indefinitely. When the limit switch is active, it causes the motor to stop abruptly, overriding the target velocity set in the previous step.
  4. Wait for 20 milliseconds.
  5. Set the target velocity in order to move the stepper motor away from the limit switch. The sign of the velocity is determined by the specified homing direction, and is the opposite of the sign chosen in step 2. The magnitude of the velocity is specified by the “Homing speed away” setting.
  6. Wait for the limit switch corresponding to the homing direction to deactivate.
  7. Halt the motor and set the current position to 0.
  8. Clear the “Position uncertain” flag.
  9. If the control mode is “Serial / I²C / USB”, command the motor to halt, disregarding other motion commands that were previously received.

The homing procedure is aborted early if the Tic receives any of these commands:

  • De-energize
  • Reset

The homing procedure is aborted early if the Tic’s control mode is set to “Serial / I²C / USB” and it receives any of the following commands:

  • Set target position
  • Set target velocity
  • Halt and set position
  • Halt and hold

The homing procedure is also aborted early if the Tic is in any operation state other than “Normal” (i.e. if an error happens), if the Tic loses power, or if the Tic is reset using the RST line.

You can tell whether the Tic is running the homing procedure by reading the “Homing active” variable documented in Section 7.

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