LAB: Timer & PWM

LAB: PWM – Servo motor and DC motor

Date: 2023-10-19

Author/Partner:

Github: repository link

Demo Video: Youtube link

Introduction

Create a simple program that control a sevo motor and a DC motor with PWM output.

You must submit

LAB Report (*.md & *.pdf)
Zip source files(main*.c, ecRCC.h, ecGPIO.h, ecSysTick.c etc...).
- Only the source files. Do not submit project files

Requirement

Hardware

MCU
- NUCLEO-F411RE
Actuator/Sensor/Others:
- 3 LEDs and load resistance
- RC Servo Motor (SG90)
- DC motor (5V)
- DC motor driver(LS9110s)
- breadboard

Software

Keil uVision, CMSIS, EC_HAL library

Problem 1: RC servo motor

An RC servo motor is a tiny and light weight motor with high output power. It is used to control rotation angles, approximately 180 degrees (90 degrees in each direction) and commonly applied in RC car, and Small-scaled robots. The angle of the motor can be controlled by the pulse width (duty ratio) of PWM signal. The PWM period should be set at 20ms or 50Hz. Refer to the datasheet of the RC servo motor for detailed specifications.

1-1. Create HAL library

Download files:

Then, change the library files as

ecTIM.h, ecTIM.c
ecPWM.h, ecPWM.c

Declare and define the following functions in your library. You must update your header files located in the directory EC \lib\.

ecTIM.h

// Timer Period setup
void TIM_init(TIM_TypeDef *TIMx, uint32_t msec);
void TIM_period(TIM_TypeDef* TIMx, uint32_t msec);
void TIM_period_ms(TIM_TypeDef* TIMx, uint32_t msec);
void TIM_period_us(TIM_TypeDef* TIMx, uint32_t usec);

// Timer Interrupt setup
void TIM_UI_init(TIM_TypeDef* TIMx, uint32_t msec);
void TIM_UI_enable(TIM_TypeDef* TIMx);
void TIM_UI_disable(TIM_TypeDef* TIMx);


// Timer Interrupt Flag 
uint32_t is_UIF(TIM_TypeDef *TIMx);
void clear_UIF(TIM_TypeDef *TIMx);

ecPWM.h

/* PWM Configuration using PinName_t Structure */

/* PWM initialization */
// Default: 84MHz PLL, 1MHz CK_CNT, 50% duty ratio, 1msec period
void PWM_init(PinName_t pinName);
void PWM_pinmap(PinName_t pinName, TIM_TypeDef **TIMx, int *chN);


/* PWM PERIOD SETUP */
// allowable range for msec:  1~2,000
void PWM_period(PinName_t pinName,  uint32_t msec);	
void PWM_period_ms(PinName_t pinName,  uint32_t msec);	// same as PWM_period()
// allowable range for usec:  1~1,000
void PWM_period_us(PinName_t pinName, uint32_t usec);


/* DUTY RATIO SETUP */
// High Pulse width in msec
void PWM_pulsewidth(PinName_t pinName, uint32_t pulse_width_ms);
void PWM_pulsewidth_ms(PinName_t pinName, uint32_t pulse_width_ms);  // same as void PWM_pulsewidth
// Duty ratio 0~1.0
void PWM_duty(PinName_t pinName, float duty);

Procedure

Make a simple program that changes the angle of the RC servo motor that rotates back and forth from 0 deg to 180 degree within a given period of time.

Reset to '0' degree by pressing the push button (PC13).

Button input has to be an External Interrupt
Use Port A Pin 1 as PWM output pin for TIM2_CH2.
Use Timer interrupt of period 500msec.
Angle of RC servo motor should rotate from 0° to 180° and back 0° at a step of 10° at the rate of 500msec.

You need to observe how the PWM signal output is generated as the input button is pushed, using an oscilloscope. You need to capture the Oscilloscope output in the report.

Create a new project under the directory \repos\EC\LAB\LAB_PWM

The project name is “LAB_PWM”.
Create a new source file named as “LAB_PWM_RCmotor.c”

You MUST write your name on the source file inside the comment section.

2. Include your updated library in \repos\EC\lib\ to your project.

ecPinNames.h ecPinNames.c
ecGPIO.h, ecGPIO.c
ecRCC.h, ecRCC.c
ecEXTI.h, ecEXTI.c
ecTIM.h, ecTIM.c
ecPWM.h ecPWM.h

Connect the RC servo motor to MCU pin (PA1) , VCC and GND
Increase the angle of RC servo motor from 0° to 180° with a step of 10° every 500msec. After reaching 180°, decrease the angle back to 0°. Use timer interrupt IRQ.
When the button is pressed, it should reset to the angle 0° and start over. Use EXT interrupt.

Configuration

Type

Port - Pin

Configuration

Circuit Diagram

You need to include the circuit diagram

Discussion

Derive a simple logic to calculate CRR and ARR values to generate x[Hz] and y[%] duty ratio of PWM. How can you read the values of input clock frequency and PSC?

Answer discussion questions

What is the smallest and highest PWM frequency that can be generated for Q1?
Answer discussion questions

Code

Your code goes here: ADD Code LINK such as github

Explain your source code with necessary comments.

// YOUR MAIN CODE ONLY
// YOUR CODE

Example Code

Sample Code : Timer Interrupt IRQ

#include "stm32f411xe.h"
#include "ecGPIO.h"
#include "ecRCC.h"
#include "ecTIM.h"


#define LED_PIN	5
uint32_t _count = 0;
void setup(void);


int main(void) {
	// Initialization --------------------------------------------------
	setup();
	
	// Infinite Loop ---------------------------------------------------
	while(1){}
}


// Initialization
void setup(void){
	RCC_PLL_init();				// System Clock = 84MHz
	GPIO_init(GPIOA, LED_PIN, OUTPUT);	// calls RCC_GPIOA_enable()
	TIM_UI_init(TIM2, 1);			// TIM2 Update-Event Interrupt every 1 msec 
	TIM_UI_enable(TIM2);
}

void TIM2_IRQHandler(void){
	if(is_UIF(TIM2)){			// Check UIF(update interrupt flag)
		_count++;
		if (_count > 1000) {
			LED_toggle();		// LED toggle every 1 sec
			_count = 0;
		}
		clear_UIF(TIM2); 		// Clear UI flag by writing 0
	}
}

Sample Code : PWM output

#include "stm32f411xe.h"
#include "math.h"

// #include "ecSTM32F411.h"
#include "ecPinNames.h"
#include "ecGPIO.h"
#include "ecSysTick.h"
#include "ecRCC.h"
#include "ecTIM.h"
#include "ecPWM.h"   // ecPWM2.h


// Definition Button Pin & PWM Port, Pin
#define BUTTON_PIN 13
#define PWM_PIN PA_5
void setup(void);


int main(void) {
	// Initialization --------------------------------------------------
	setup();	
	
	// Infinite Loop ---------------------------------------------------
	while(1){
		LED_toggle();		
		for (int i=0; i<5; i++) {						
			PWM_duty(PWM_PIN, (float)0.2*i);			
			delay_ms(1000);
		}		
	}
}


// Initialiization 
void setup(void) {	
	RCC_PLL_init();
	SysTick_init();
		
	// PWM of 20 msec:  TIM2_CH1 (PA_5 AFmode)
	GPIO_init(GPIOA, 5, EC_AF);
	PWM_init(PWM_PIN);	
	PWM_period(PWM_PIN, 20);   // 20 msec PWM period
}

Results

Experiment images and results

Show experiment images /results

Add demo video link

Problem 2: DC motor

Procedure

Make a simple program that rotates a DC motor that changes the duty ratio from 25% -->75%--> 25% --> and so on.

The rotating speed level changes every 2 seconds.

By pressing the push button (PC13), toggle from Running and stopping the DC motor

First, you MUST read Tutorial: DC motor driver connection

Use the same project.

Create a new source file named “LAB_PWM_DCmotor.c”
You need to eliminate the other source file that contains main() from the project
- e.g. Eliminate "“LAB_PWM_RCmotor.c” from the project

You MUST write your name on the source file inside the comment section.

Connect DC motor and DC motor driver.

PA_0 for the DC motor PWM
PC_2 for Direction Pin

Change DC motor from LOW Speed to HIGH Speed for every 2 seconds

e.g. 25% -->75%--> 25% --> and so on.

When Button is pressed, it should PAUSE or CONTINUE motor run

Configuration

Function

Port - Pin

Configuration

Circuit Diagram

You need to include the circuit diagram

Code

Your code goes here: ADD Code LINK such as github

Explain your source code with necessary comments.

// YOUR MAIN CODE ONLY
// YOUR CODE

Results

Experiment images and results

Show experiment images /results

Add demo video link

Reference

Complete list of all references used (github, blog, paper, etc)

Troubleshooting

1. motor PWM duty ratio for different DIR

When, DIR=0 duty=0.8--> PWM 0.8 // 실제 모터에 전달되는 pwm

Whe, DIR=1 duty=0.8--> PWM 0.2 // 실제 모터에 전달되는 PWM

*** a solution ***

float targetPWM;  // pwm for motor input 
float duty=abs(DIR-targetPWM); // duty with consideration of DIR=1 or 0

PWM_duty(PWM_PIN, duty);

2. Print a string for BT (USART1)

Use sprintf()

#define _CRT_SECURE_NO_WARNINGS    // sprintf 보안 경고로 인한 컴파일 에러 방지
#include <stdio.h>     // sprintf 함수가 선언된 헤더 파일

char BT_string[20]=0;

int main()
{
	sprintf(BT_string, "DIR:%d PWM: %0.2f\n", dir, duty);    // 문자, 정수, 실수를 문자열로 만듦
	USART1_write(BT_string, 20);
	// ...
}

https://dojang.io/mod/page/view.php?id=352 **

3. Motor does not run under duty 0.5

SOL) Configure motor PWM period as 1kHa

4. Check and give different Interrupt Priority

Check if you have different NVIC priority number for each IRQs

(Option) You can write Troubleshooting section

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