Driving stepper motors using STM8A and STM8S microcontrollers

AN3208

12/19

Doc ID 17411 Rev 1

A negative sign shows the current flow in the reverse direction. The current flowing through

each motor coil is controlled using one PWM output (PWMx) and one I/O port (configured in

output push-pull mode) as shown in Figure 11. PWM channels are configured to provide the

required waveform in synchronization with the GPIOs.

Figure 11.

Stepper motor configuration pin

When the I/O output is 0, the current through a coil flows in one direction and when the I/O

output is 1, the current flows in the reverse direction.

Step-by-step explanation of Table 1:

●

Step 1: Coil 1 and coil 2 have the same magnitude (0.87, duty cycle 87 %) and in both

coils the current flows in the same direction, I/O value for both coils is 0.

●

Step 2: The magnitude of coil 1 is 0.71 (duty cycle 71 %) and the magnitude of coil 2 is

0.97 (duty cycle 97%). The currents in both coils flow in the same direction, I/O value

for both coils is 0.

.

.

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Step 6: The magnitude of coil 1 is 0.71 (duty cycle 71 %) and the magnitude of coil 2 is

-0.26 (duty cycle 26 %). The currents in the two coils flow in the opposite direction. I/O

value for coil 1 is 0, I/O value for coil 2 is 1.

For more details about duty cycle calculation see Section 5.2: Software description.