Generate specified number of pulses on STM32

In today’s industrial landscape, servo and stepper motor integration has become ubiquitous across every sector. Stepper motors excel in precise position control applications. On the other hand, servo motors provide a versatile array of control modes, including position control, speed regulation, torque management, and more.

Position control, a fundamental requirement in many applications, is commonly achieved through Pulse Train Output (PTO) mechanisms. Almost all Programmable Logic Controllers (PLCs) now incorporate PTO functionalities, such as the DPLSY instruction in Delta PLCs and PTO instruction in Siemens PLCs. In this post, we will program STM32 to generate PTO. find the code on GitHub

Three Methods for PTO Generation:

Through For Loop:

• Through For Loop:Description: Simplest method.Pros: No special peripheral required.Cons: Halts system until specified pulses are reached.

Through Interrupt:

• Through Interrupt:Description: More efficient method.Pros: No halting of program execution.Cons: Efficiency depends on CPU clock speed and other tasks. Suitable for low-speed PTO.

Through Timer:

• Through Timer:Description: This is the most efficient but complex method.Pros: Highest PTO speed achievable.Cons: Requires timer peripheral. Does not require CPU attention except when the pulse number is reached.

we will implement PTO generation through timers. STM32 timers have many modes of operation. TIM14 is configured as PWM (50% duty cycle), and pin PA7 is mapped to channel 1 of TIM14 mapped on alternate function four (AF4), this pin is our output. Time TIM3 is configured as an external clock counter ( SMS=111 in the TIMx_SMCR register), trigger input to synchronize the counter TS=3 in the TIMx_SMCR register. TIM3 will count pulses on OC1 of timer 14 and the interrupt will trigger when the count register value reaches the ARR register ( TIM3->CNT== TIM3->ARR)

Code Execution

Code generates pulses with direction, tim3_pulse_counter_init(5) function with argument value 5 will generate 5 pulses in the forward direction and 5 pulses in the reverse direction.