Lesson 1: Part 3: Controlling GPIO - On-Board Output - LED Control

In this section we will be using what we learn from Part 1 and write some C code. Recite from Part 1, 3 configurations is require as below:

1. Enable GPIO section for respective pin
• SFR: RCC_AHBENR , bit: IOPCEN, value: 1
2. Pin to be output function
• SFR: GPIOC_MODER, bit: MODER9, value: 01
3. Control the pin to be high state or low state
• High state: SFR: GPIOC_ODR, bit: ODR 9, value: 1
• Low state:  SFR: GPIOC_ODR, bit: ODR 9, value: 0

In order to access SFR in C language, we need to include a header files :

•  #include stm32f0xx.h

 Open content of stm32f0xx.h by right click on source code file name, select 'Open document' as shown below:

Open SFR Define File

Inside the SFR files define all the SFR that we use in source code below.

Then the corresponding C code for 3 cases above are:

1. Enable GPIO section for respective pin
• RCC->AHBENR |= RCC_AHBENR_GPIOCEN;
2.  Pin to be output function
• GPIOC->MODER &= ~GPIO_MODER_MODER9;  //mask the bit to 00
• GPIOC->MODER |= MODE_OUTPUT;         //set the bit
3.  Control the pin to be high state or low state
• High state:
• GPIOC->ODR |= GPIO_ODR_9;
• Low state:
• GPIOC->ODR &= ~GPIO_ODR_9;

Below is the image for whole source code. You can either type out or just use Git link here.

Full Source Code To Control LD3

Real life applications:

1. With proper hardware circuit, instead of turn on/off LED, we can turn on/off fan, light.
2. Replacing the LED with IR transmittor, and with correct timing on turning on/off, we can use it as remote control, to control electrical appliances: TV, DVD.

Exercise

1. In the source code we have turn on LED and turn off LED, why the LED is constantly turn on when program is running?
2. Repeating Part 1 to 3 process, this time try controlling LD4 LED