Kart/stepper motor controller
The kart's stepper motor controller FPGA generates 4 coil driving signals and receives a stepper end input.
It has a step angle of 7.5°, and as such 48 steps per turn.
The cables are connected as follows:
The stepper motor controller has to generate the 4 phases to turn the kart's steering wheels to the desired angle.
To begin with, the design environment has to be downloaded.
It comprises the
stepperMotorController block contains the provided I2C bus interface
and an empty
angleControl block which is to be designed.
The block receives a
target unsigned number and has to step the coils at each occurrence of the
enStep signal until the desired angle is reached.
The current in the coils is given by the 4 outputs
The steering angle,
actual, is estimated with the help of a counter which increments or decrements each time when when the coil control signals change.
The block provides the estimated angle,
actual, together with a logic signal,
reached, telling if the desired angle has been reached.
A switch contact, providing the signal
stepperEnd, has to be mechanically fitted on the kart in order set one end of the wheels' direction movement.
As soon as
stepperEnd is activated, the stepper motor is stopped and the
actual angle is reset.
With this, the steering motor will not try to turn further than what the kart's mechanical structure allows it to in one of the directions.
In the other direction, it is the programmer's task not to request a too large
This also means that the angles are always considered as positive numbers, the zero position being given by the
- In order to limit the current consumption, turn off the current in all the coils when the stepper motor is not turning any more.
- Make sure that both the first and the last pulse of the coil control signals have the same duration as all the others.