Could somebody guide me as to how to compute Precaler,Duration,dutycycle and period for STM32f469NI-eval board Timer

[Suraj Vanjeeswaran]

Posted on April 12, 2017 at 09:28

I am trying to setup PWM to control Stepper Motor using stm32cubemx code initialiser with keil IDE, I need a max duty cycle of 50% at a frequency 12MHz. I am trying to obtain proper values for prescaler, autoreload(duration) and period for configuring my timer for the above configuration.

[Nesrine M_O]

Posted on April 12, 2017 at 13:20

Hi

Vanjeeswaran.Suraj

,

Please try to start from ready examples under te STM32cubeF4 firmware package:

• STM32Cube_FW_F4_V1.0\Projects\STM32469I_EVAL\Examples\TIM\TIM_PWMOutput
• STM32Cube_FW_F4_V1.0\Projects\STM32469I_EVAL\Examples\TIM\TIM_7PWMOutput

Refer also to

http://www.st.com/content/ccc/resource/technical/document/application_note/group0/91/01/84/3f/7c/67/41/3f/DM00236305/files/DM00236pdf/jcr:content/translations/en.DM00236pdf

application note it may help you.

-Nesrine-

[Suraj Vanjeeswaran]

Posted on April 13, 2017 at 12:16

Thanks for your reply Nesrine. I'll post back after trying  out the example projects mentioned by you.

[Tesla DeLorean]

Posted on April 13, 2017 at 21:59

>>

I am trying to setup PWM to control Stepper Motor using stm32cubemx code initialiser with keil IDE, I need a max duty cycle of 50% at a frequency 12MHz. I am trying to obtain proper values for prescaler, autoreload(duration) and period for configuring my timer for the above configuration.

180 / 12 = 15

168 / 12 = 14

Prescaler wants to be 0 ie 1 -1, Period wants to be 14 ie 15-1 for a 180 MHz clock source (TIMCLK, so APB2)

The Pulse = 15 / 2, but has to be an integer, so that won't be exactly 50/50. If that's an absolute must you'll need to run at 168 MHz

You are also not going to have a lot of choices of pulse width at this frequency

[Suraj Vanjeeswaran]

Posted on April 14, 2017 at 11:38

Thanks for providing me the values Clive One I shall try them out and post back here

[Suraj Vanjeeswaran]

Posted on April 14, 2017 at 12:36

Hello Clive One,

I tried to control my stepper motor using the values for prescaler,Counter Period and duty cycle  provided by you,But unfortunately my stepper motor does not rotate,it just generates a humming noise.I even tried reducing the Timer Out Clock frequency to 2KHz by using these values

Prescaler=0

Counter Period =[(90MHz/2KHz)-1]=45000-1=44999                            (my timer Timer 3 is connected to APB1 ) 

Duty Cycle=4499*(50/100)=22,499.5 I took 22,499   for 50% duty cycle

My motor currently works with PWM for the following  Timer Parameters

Prescaler=1

Counter Period=65535

duty cycle= 65535*(50/100)=32767.5 or 32767 integer value for 50% duty cycle

I am trying to rotate my motors at a desired speed of 540RPM, With the above parameters I am only getting a speed of 180RPM.I would be very grateful if you could guide me as to how to achieve the desired speed for stepper motor using PWM.

-Suraj Vanjeeswaran 

[Suraj Vanjeeswaran]

Posted on April 14, 2017 at 13:01

Hello Nesrine,

I tried out the example project TIM_PWMOutput located in STM32Cube_FW_F4_V1.15.0\Projects\STM32469I_EVAL\Examples\TIM\TIM_PWMOutput

wherein the PWM output(Step Pin) is taken from PC6. I modified the example to add a new Pin PA2 as GPIO_Output for setting DIR for the stepper motor. But I am not able to get the motor to rotate with this,kindly advise if I am missing something here.Also I would be grateful if you could provide me some example program based on stm32cubemx to control a stepper motor using STM32F469NI-eval board interfaced  with A4988A Pololu stepper drivers. 

-Suraj Vanjeeswaran