![]() Now we can read the GPIO pins like below.īool value = (( GPIOB->IDR > 15 ) & 0x1) Let’s assume that I have configured PORT B as input, using the GPIOB_MODERregister and other control registers. You have to read the whole register.īits – Reserved (Must be kept at reset value). Which means you cannot read a single bit. And It can be accessed in 32-bit word mode only. This will be containing the corresponding value of the corresponding I/O port. Please find the below image of the GPIOx_IDRregister.īits – IDRy : Port Input Data, (y = 0 … 15) When you configure the GPIO ports as input using GPIOx_MODERregister, this register is used to get the value from the GPIO pin. Here 2-bits are combined for one particular GPIO pin.īits – OSPEEDRy : Speed selection for port X and bit Y, (y = 0 … 15) Please find the below image of the GPIOx_OSPEEDRregister. This GPIO Output speed register is used to set the speed of the GPIO pin. Please find the below image of the GPIOx_OTYPERregister.īits – OTy : Port output type, (y = 0 … 15)īits – Reserved (Must be kept at reset value). ![]() Got some idea about both output modes? Okay, let’s go to the register now. And if you write low to the GPIO, then the switch will be connected to the ground. So when you write High to the GPIO pin, the switch will be connected to the Vcc/Vdd. One switch is connected to Vcc/Vdd and another switch is connected to the ground. Whereas in push-pull mode, two switches (transistor/MOSFET) will be there inside of the microcontroller. That’s why we are using a pullup 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). SET_BIT(RCC->AHB1ENR, RCC_AHB1ENR_GPIOAEN) These are a couple of ways of enabling AHB clock for Port A We don’t need the rest of the bits as we are only working on GPIO. The register is given below.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 This is called as RCC AHB1 peripheral clock enable register. I have classified these register into 4 types based on their operation.īefore looking into the control register, we will see the Clock Register ( RCC_AHB1ENR) which will enable the AHB clock to the GPIO ports. There are a couple of registers used in GPIO. STM32 GPIO Tutorial – Registers used in STM32 GPIO Highly flexible pin multiplexing allows the use of I/O pins as GPIOs or as one of several peripheral functions.Fast toggle capable of changing every two clock cycles.Alternate function input/output selection registers (at most 16 AFs per I/O).Locking mechanism ( GPIOx_LCKR) provided to freeze the I/O configuration.Bit set and reset register ( GPIOx_BSRR) for bitwise write access to GPIOx_ODR.Input data to input data register ( GPIOx_IDR) or peripheral (alternate function input).Input states: floating, pull-up/down, analog.Output data from output data register ( GPIOx_ODR) or peripheral (alternate function output).Output states: push-pull or open-drain + pull-up/down.STM32F401VE has five ports mentioned below. GPIO stands for “General Purpose Input/Output.” We are using STM32F401VE for our examples. 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.STM32 GPIO Tutorial – Registers used in STM32 GPIO.Once finished, you can turn on the circuit to test it. You can choose to apply direct or alternate current to the circuit. (contacts, switcher, resistors, LED, diodes, amplifiers, transistors, voltmeter, ammeter, etc.). The program allows you to draw circuits using the right symbols, included in the program. Solve Elec features an oscilloscope and performs frequency response graphs. This program allows you to get literal formulas and values for current intensities and voltages defined in the circuit, verify circuit related equations, get the equivalent circuit of displayed circuit, browse the integrated documentation and edit, save and print reports. edit, save and print reports made of various elements displayed in main window.get the equivalent circuit of displayed circuit.get literal formulas and values for current intensities and voltages defined in the circuit.draw and analyze electrical circuits functioning in direct or alternating current.
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