1. Asst. Prof. Dr. Alper ŞİŞMAN
Practice 2
Asst. Prof. Dr. Alper ŞİŞMAN

2. GPIO Module Output states: push-pull or open drain + pull-up/down
Output data from output data register (GPIOx_ODR) or peripheral (alternate function output)
Speed selection for each I/O
Input states: floating, pull-up/down, analog
Input data to input data register (GPIOx_IDR) or peripheral (alternate function input)
Bit set and reset register (GPIOx_BSRR) for bitwise write access to GPIOx_ODR

3. Locking mechanism (GPIOx_LCKR) provided to freeze the I/O configuration
Analog function
Alternate function input/output selection registers (at most 16 AFs per I/O)
Fast toggle capable of changing every two clock cycles
Highly flexible pin multiplexing allows the use of I/O pins as GPIOs or as one of several peripheral functions
During and just after reset, the alternate functions are not active and the I/O ports are configured in input floating mode.

4. The configuration steps of GPIO pin
The clock signal of corresponding GPIO HW must be activated:
RCC->AHB1ENR: Reset&Clock control reg.->AHB1 enable register.
The pins must be defined as input or output
GPIOD->MODER: Mode register 32-bit for 16 pins:

5. The output type must be configured
GPIOD=>OTYPER:
The output speed must be configured
GPIOD=>OSPEEDR: 32 bit register for 16 pins.

6. The pull up resistor configuration mus be set
GPIOD=>PUPDR: 32 bit reg.16 pins

7. Read/Write Registers GPIO port input data register: GPIOD=>IDR
GPIO port output data reg.:GPIOD=>ODR
GPIO port bit set/reset reg.: GPIOD=>BSRR

8. Other GPIO Registers GPIO port configuration lock reg.
GPIO alternate function low reg.
GPIO alternate function high reg.
Further information can be seen on page 278. (ref manual RM0090)

9. Blinking LED #include "STM32F4xx.h” void SystemInit() {
Run in DEBUG mode step by step and see four LED in on and off.
#include "STM32F4xx.h”
void SystemInit() {
(*((int*)0xE000ED88))|=0x0F00000; // Floating Point donanimini aktiflestir.
RCC->AHB1ENR |= 0x ; // GPIOD donaniminin clock sinyalini uygulayalim
GPIOD->MODER = 0x ; // GPIOD nin 15, 14, 13, 12 pinleri cikis tanimlandi (Ledler bu pinlerde)
GPIOD->OSPEEDR= 0xFFFFFFFF; // GPIOD nin tum cikislari en yuksek hizda kullanacagiz }

10. int main() {
while(1)
GPIOD->ODR= 0x0000F000; // Ledler yansin
GPIOD->ODR= 0x ; // Ledler sonsun }

11. Add a delay subrotine void delayy(){ int delay0 = 0x000FFFFF;
while (delay0--){ }

12. Call delayy from main int main() { while(1)
GPIOD->ODR= 0x0000F000; // Ledler yansin
delayy();
GPIOD->ODR= 0x ; // Ledler sonsun }

13. Read Button Activate GPIOA clock
Configure A0 as input (it is default), bus speed and no pull up/down
void SystemInit() {
(*((int*)0xE000ED88))|=0x0F00000; // Floating Point donanimini aktiflestir.
RCC->AHB1ENR |= 0x ; // GPIOD &A donaniminin clock sinyalini uygulayalim
GPIOD->MODER = 0x ; // GPIOD nin 15, 14, 13, 12 pinleri cikis tanimlandi (Ledler bu pinlerde)
GPIOD->OSPEEDR= 0xFFFFFFFF; // GPIOD nin tum cikislari en yuksek hizda kullanacagiz
GPIOA->OSPEEDR= 0xFFFFFFFF; // GPIOA nin tum girisleri en yuksek hizda kullanacagiz
GPIOA->PUPDR = 0x ; }

14. Stop blinking When button is pressed the blinking will stop:
int main() {
while(1)
while ((GPIOA->IDR & 0x1) == 0){ }
GPIOD->ODR= 0x0000F000; // Ledler yansin
delayy();
GPIOD->ODR= 0x ; // Ledler sonsun

15. Define D0 as output&observe it
void SystemInit()
{ (*((int*)0xE000ED88))|=0x0F00000; // Floating Point donanimini aktiflestir.
RCC->AHB1ENR |= 0x ; // GPIOD &A donaniminin clock sinyalini uygulayalim
GPIOD->MODER = 0x ; // GPIOD nin 15, 14, 13, 12 ve 0. pinleri cikis tanimlandi (Ledler bu pinlerde+0. pin)
GPIOD->OSPEEDR= 0xFFFFFFFF; // GPIOD nin tum cikislari en yuksek hizda kullanacagiz
GPIOA->OSPEEDR= 0xFFFFFFFF; // GPIOA nin tum girisleri en yuksek hizda kullanacagiz
GPIOA->PUPDR = 0x ;}

16. HW#2 Connect a 7-segment to the STM32F4x board
Write a number between 1-9 on the 7-segment
When user button is pressed number 0 should be seen on the 7-segment.