Some GPIO pins on our controller support True Open Drain (T) and High Sink Current (HS) as mentioned in the above image. This determines the GPIO Speed, if you want to switch your GPIO pins between high and low very fast, then we can choose Fast output. To put it simple, an Open Drain output pin can make the output only as low not as high, while a push-pull output pin can make the output both as high as well as high.Īpart from that from the above table, you can also notice that an output pin can either be Fast output (10 Mhz) or Slow Output (2 MHz). The difference between Open Drain and Push-Pull Output pins is already discussed, hence we won’t get into details of that. The input pins on our microcontroller can either be floating or weak pull-up and the output pins can either be Open Drain or Push-pull. For the STM8S103F3P6 microcontroller pin description details that are mentioned in the datasheet are shown below images. The best to avoid the traps is to read the pin details and pin description provided in the STM8S103F3P6 datasheet. But I deliberately brought this up to provide me an opportunity to show you some common traps that you might fall into when selecting GPIO pins on a new microcontroller. Truly speaking, it would not hurt to use PA1 an input pin and it would just work pin. Pinout Description and Tips for STM8S103F GPIO Selection Sadly, the on-board LED is connected to this pin, so we don’t have much of a choice here, and in this program, we are not going to use I2C, so it's not much of a problem. So, if we use this pin for simple GPIO purposes like connecting an LED, then we won’t be able to use I2C and the LED at the same time. For example, the PB5 (pin 5 of PORT B) can not only work as a GPIO pin but also as an SDA pin for I2C communication and as a Timer 1 output pin. Each GPIO pin is also clubbed with some other special functionality. Now coming back to the question, why PA2 for input and why PA3 for output? To understand that, let's take a closer look at the pinout of the microcontroller which is shown below.Īs per the pinout diagram, we have four ports on our microcontroller, namely, PORT A, B, C, and D denoted by PA, PB, PC, and PD respectively.
As you can see, I have also connected my ST-link programmer to programming pins which will not only program our board but will also act as a power source. My hardware set-up for this tutorial is shown below.
The on-board Led is already connected to PB5 (pin5 of PORTB), so I have just connected an LED to PA3 and a push-button to PA2, as you can see in the diagram below.īut, of all the output pins available on our controlled why did I select PA3 for output and PA2 for input? The questions are valid and I will explain that later in this article. The idea is to learn all the GPIO functionality in a simple set up. As mentioned early, we will be using two LEDs here, one is an onboard LED which will blink continuous and the other is an external LED which will be toggled with a push button. Getting the Hardware Readyīefore we dive into the program, let get the hardware connections ready. If you are completely new, it is highly recommended to read the previous tutorial before you proceed any further.
#Stm8 cosmic example how to#
The board already has an onboard LED connected to pin 5 of port B, we will learn how to blink this LED and also add an external LED and control it with a push-button. In this tutorial, we will learn how to perform general GPIO functions on STM8S controllers. With all the basics covered, lets actually start writing code.
#Stm8 cosmic example code#
We have also learned how to use the standard peripheral libraries, and how to compile and upload the code into our microcontroller. In our previous tutorial, we learned how to get started with STM8S103F3 Development Board and how to set up the IDE and compiler to program our STM8S controllers. For microcontrollers, an LED blinking program is equivalent to the “hello world” program.
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