3.3.1.1.1 Speed Mode

Speed Mode allows the user to spin the stepper motor continuously at a desired speed. The user configures the starting speed, stopping speed, acceleration rate, and target speed. Stepper controls are enabled only when ‘Motor Driver' control is enabled. ‘Start Steps’ button is enabled only when ‘Driver Outputs' control is enabled for example, EN/nFault pin is set to high. When the ‘Start Steps’ button is clicked, the motor begins spinning at the starting speed and accelerates to the target speed according to the configured acceleration rate. The acceleration profile in the microcontroller firmware accepts the starting-speed PPS signal and target-speed PPS signal as a clock cycle number.

When the ‘Start steps’ button is clicked, the PWM timer generates steps at a rate specified by the 'Starting Speed' PPS parameter. When ‘Stop Steps’ is clicked, the motor starts decelerating at the ‘Acceleration Rate’ configured to reach the stopping speed and eventually stop. The configuration is visualized by the embedded graph shown on the GUI screen.

When accelerating or decelerating, the PPS signal is adjusted every 32 ms based on the integer value of PPSPS / 32 ms. Acceleration rates must be between 1 and 65,535 PPSPS. The step rate increases by the calculated value until the target speed is reached.

The starting speed must be less than or equal to the target speed. If the starting speed and target speed are equal, the EVM firmware will not perform an acceleration routine. The stopping speed must also be less than or equal to the target speed. The target speed is limited to a range between 200 and 65,535 PPS.

The 'Start Steps' command computes how frequently automatic speed updates are issued and a second timer is used to change the speed according to the programmed acceleration rate profile. Once clicked, the motor will begin spinning according to the parameters set in the GUI.

When the target speed PPS value is reached, the acceleration profile ends and the motor continues running until the 'Stop Steps' button is clicked. When the stepper is commanded to stop, the controller performs the same actions as it did while accelerating, but in reverse order to decelerate until the stop speed PPS value is reached, in which case the motor fully stops.

Figure 6 shows the acceleration profile and the role each parameter plays during speed computation.