![]() That’s why we are using a pull-up resistor for the open-drain pins. If you write low to the GPIO pin, it will be left floating since the switch will be turned off. So If you write high to the GPIO pin using software, it will be connected to the ground through the switch. In open-drain mode, inside the microcontroller one switch (transistor/ MOSFET) is connected to the GPIO pin and the ground. If you have worked on I2C you must have heard this. First, we need to know what is push-pull and open drain. This is the GPIO output type register which is used to select the output type (Push-Pull or Open Drain). So, we will use either Input mode or output mode. In this tutorial, we are using only the I/O operation. Here 2-bits are combined for one particular GPIO pin.īits – MODERy: Direction selection for port X and bit Y, (y = 0 … 15)Ġ0: Input (reset state) 01: General purpose output mode 10: Alternate Function mode 11: Analog mode Please find the below image of the GPIOx_MODERregister. This GPIO port mode register is used to select the I/O direction. GPIO Port Pullup/Pulldown register ( GPIOx_PUPDR).GPIO Port output speed register ( GPIOx_OSPEEDR). ![]() GPIO Port output type register ( GPIOx_OTYPER).The below control registers are used to configure the GPIOs. SET_BIT(RCC->AHB1ENR, RCC_AHB1ENR_GPIOAEN) We don’t need the rest of the bits as we are only working on GPIO.Įxample: //These are a couple of ways of enabling AHB clock for Port A You can go to the section directly based on the microcontroller that you have.īit – GPIOAEN: IO port A clock enableīit – GPIOBEN: IO port B clock enableīit – GPIOBEN: IO port C clock enableīit – GPIOBEN: IO port D clock enableīit – GPIOBEN: IO port E clock enable In this post, we have used three microcontrollers ( STM32F1, STM32F4, STM32F7) for demonstration. Please click the controller-specific tab and see the content properly. If you have any one of the controllers or ARM cortex, you can use that. In this tutorial, we are going to see the timer for the below three STM32 controllers. STM32 GPIO Tutorial – Switch/Button Interfacing with STM32īefore starting this STM32 GPIO Tutorial, Please go through the below tutorials.STM32 GPIO Tutorial – LED Interfacing with STM32.GPIO Port configuration lock register (GPIOx_LCKR).Port bit set/reset register (GPIOx_BSRR).GPIO Port output data register (GPIOx_ODR):.GPIO Port input data register (GPIOx_IDR).GPIO Port configuration register high (GPIOx_CRH).GPIO Port configuration register low (GPIOx_CRL).You can use the interactive tool below to test this yourself. On the other hand, a PWM with a resolution of 8 bits will have 256 discrete levels for the duty cycle over the entire range (from 0% up to 100%). The higher the PWM resolution, the higher number of discrete levels over the entire range of the PWM’s duty cycle.Ī PWM resolution of only 3 bits means there are only 8 discrete levels for the duty cycle over the entire range (from 0% up to 100%). The PWM resolution can be as the number of discrete duty cycle levels between 0% and 100%. It’s the number of bits that are used to represent the duty cycle value. The PWM resolution is expressed in (bits). That’s why we typically change the duty cycle to control things like LED brightness, DC motor speed, etc. And it directly affects the PWM’s total (average) voltage that most devices respond to. The duty cycle is usually expressed as a percentage ( %) value because it’s a ratio between two-time quantities. The PWM’s duty cycle equation is as follows: It’s a measure of how long the PWM signal stays ON relative to the full PWM’s cycle period. ![]() The PWM’s duty cycle is the most important feature that we’re always interested in. Here is how it looks graphically and its mathematical formula. The frequency is measured in Hz and it’s the inverse of the full period time interval. The first of which is the frequency, which is basically a measure of how fast the PWM signal keeps alternating between HIGH and LOW. This technique is widely used in embedded systems to control LEDs brightness, motor speed, and other applications. Certain loads like (LEDs, Motors, etc) will respond to the average voltage of the signal which gets higher as the PWM signal’s pulse width is increased. Pulse Width Modulation ( PWM) is a technique for generating a continuous HIGH/LOW alternating digital signal and programmatically controlling its pulse width and frequency. And without further ado, let’s get right into it! Previous Tutorial Tutorial 16 Next Tutorial STM32 PWM Example – STM32 Timer PWM Mode & LABs STM32 Course Home Page □ Table of Contents And how to set up the timer module to operate in PWM mode and write a simple application to make an LED dimmer. You’ll get to know how the PWM signal is generated, how to control its frequency, duty cycle, and how to estimate the PWM resolution. In this tutorial, we’ll discuss the STM32 PWM generation using STM32 timer modules in the PWM mode.
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