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STM8S105K4 Microcontroller: Overview, Key Features, and Practical Applications

The STM8S105K4 microcontroller, known for its efficiency and versatility, is a solid choice for embedded applications in consumer electronics and industrial systems. This article provides an overview of its key features, pin configuration, and block diagram, along with a step-by-step guide to setting up a project in IAR Embedded Workbench. With example code for basic GPIO control and instructions on programming and debugging, this guide will help you get started with the STM8S105K4 quickly and effectively.

Overview

The STM8S105K4 is an 8-bit microcontroller from STMicroelectronics, part of the STM8 family. It is designed for a wide range of applications, providing a balance of performance, power efficiency, and affordability. With its advanced peripherals and embedded EEPROM, the STM8S105K4 is suitable for general-purpose control tasks in consumer electronics, industrial systems, and more.

Features and Specifications

Core: 8-bit STM8 core with Harvard architecture, operating at up to 16 MHz.
Memory:
- Flash memory: 16 KB
- RAM: 1 KB
- EEPROM: 640 bytes
Timers:
- 16-bit advanced control timer (TIM1)
- 16-bit general-purpose timer (TIM2)
- 8-bit basic timer (TIM4)
Communication Interfaces:
- UART, I²C, and SPI interfaces for versatile connectivity.
Analog Features:
- 10-bit ADC with up to 5 channels
- Internal voltage reference for enhanced analog precision
GPIO:
- Multiple I/O pins with programmable pull-up, output type, and speed settings
- Up to 38 I/O ports (depending on the package)
Operating Voltage: 2.95 V to 5.5 V
Temperature Range: -40°C to +85°C (industrial-grade)
Packaging: Available in LQFP32 and other compact package options.

Pin Configuration

The STM8S105K4 provides up to 48 I/O pins depending on the package, which can be configured for multiple functions such as ADC input, PWM output, UART, SPI, I²C, and general-purpose digital I/O. Key GPIOs include:

Port A (PA0 to PA7): Configurable for digital I/O and alternate functions.
Port B (PB0 to PB7): Primarily used for I/O with specific pins supporting alternate functions.
Port C, D, and E: Support for additional I/O, analog input, and timer functions, including PWM generation.

Each pin can be configured individually for input or output, with support for both push-pull and open-drain modes. Additionally, the pins are ESD-protected and capable of high-drive outputs for LED and relay driving applications.

Block Diagram

The block diagram of the STM8S105K4 includes:

Core: STM8 core with clock control, program counter, and ALU for 8-bit processing.
Memory Units:
- Flash memory for code storage
- EEPROM for data retention
- SRAM for general-purpose usage
Peripherals:
- ADC for analog signal processing
- Timers (TIM1, TIM2, and TIM4) for event timing, PWM, and waveform generation
- Communication interfaces (UART, SPI, and I²C) for connectivity with sensors, displays, and other modules
System Control:
- Clock generation unit with internal and external clock sources
- Watchdog timer for system reliability
- Power management unit with low-power modes
I/O Control: GPIO configuration and management for interfacing with external devices

This modular architecture allows for flexibility in handling a variety of tasks, from real-time control to serial communication.

Applications

The STM8S105K4 microcontroller is ideal for a wide range of applications, including:

Consumer Electronics: Home appliances, remote controls, and display control
Industrial Control: Motor control, HVAC systems, and PLC modules
Automotive Applications: Sensor interfacing, dashboard control, and lighting systems
Healthcare: Medical devices, monitoring systems, and portable health equipment
IoT Devices: Smart sensors, wireless modules, and energy metering

With its mix of analog, digital, and communication features, the STM8S105K4 enables designers to create efficient, versatile, and cost-effective embedded systems across various industries.

Creating an IAR Project for STM8S105K4

In this example, we’ll create an IAR project to light up the led using the STM8S105K4 microcontroller.

Required Tools

Hardware Components:

STM8S105K4 Microcontroller
ST-LINK/V2 Debugger and Programmer
STM8S105K4 Development Board (optional)
LED and Resistor (1KΩ)
Breadboard and Jumper Wires

Software Tools:

IAR Embedded Workbench for STM8
ST Visual Programmer (STVP)

Steps to Create the Project

Create Project Folder:

- Create a folder named test, and within it, create another folder named user.

Open IAR Embedded Workbench:

- Open IAR for STM8 (version 9.40.2).

Create a New Project:

- Go to Project -> Create New Project.
- In the dialog box, select STM8 Series -> Empty project, and click OK.
- Save the .ewp file in the test/user folder and name it test.

Add Project Group:

- Target the menu and click Project -> Add Group.
- Name the group user, and click OK.

Create a Main File:

- Go to File -> New -> File, then save it as main.c.
- Add main.c to the user group.

Configuring the IAR Environment

Project Options:

- Target and click Project -> Options.

Set Target Device:

- In General Options -> Target -> Device, select STM8S105K4 (or your specific device model).

Configure Include Paths:

- In C/C++ Compiler -> Preprocessor, add the path "$PROJ_DIR$\..\user".
- This syntax specifies the include file path within the project directory.

Setup Debugger:

- In Debugger -> Setup, set the Driver to ST-LINK.
- Click OK to save the configuration.

Add Code and Build the Project:

- In main.c, enter the following code, then go to Project -> Rebuild All.
- If you see Total number of errors: 0 and Total number of warnings: 0, the project is set up correctly.

Include Header File:

- Ensure the header file IOSTM8S105K4.h is available in the IAR installation directory:
  Software (E:) > IAR for STM8 > arm > inc > ST.

Writing, Downloading, and Debugging Code

The following code toggles an LED connected to pin PE5 with a delay loop to make the LED blink.

				
					#include "iostm8s105k4.h"  // Ensure this header file exists in your project

int main(void) {
    int i, j;  // Variables for delay loop

    // Configure PE5 as an output pin
    PE_DDR |= 0x20;   // Set bit 5 of PE_DDR (PE5) to 1 to configure as output
    PE_CR1 |= 0x20;   // Set bit 5 of PE_CR1 to 1 for push-pull mode
    PE_CR2 &= ~0x20;  // Set bit 5 of PE_CR2 to 0 for low speed

    // Main loop
    while (1) {
        PE_ODR ^= 0x20;  // Toggle PE5 (connected to LED)

        // Simple delay loop
        for (i = 0; i < 100; i++) {
            for (j = 0; j < 1000; j++) {
                // Empty loop for delay
            }
        }
    }
}

Hardware Connections

PE5 → LED → 1K Resistor → Ground

After uploading the code and starting the program, you should see the LED on PE5 blinking, confirming that the project setup is complete.

Drive a Passive Beeper by STM8S105K4

In this example, the STM8S105K4 microcontroller’s pin PD4 is used to drive a passive beeper. The beeper function is an alternate function of PD4. By configuring the AFR7 bit, we can enable the alternate function for PD4, which allows it to drive the beeper.

Code Execution

				
					/* Includes */
#include "user.h"

/* Function Prototypes */
void HalBeep_Init(BEEP_Frequency_TypeDef beep_fre);

/* Main Function */
void main(void)
{
    /* Clock, LED, and Timer Initialization */
    HalCLK_Config();
    HalLed_Init();
    HalTimer1_Init();
    // HalUART2_Init(); // Uncomment if UART is required
    
    /* Buzzer Initialization */
    HalBeep_Init(BEEP_FREQUENCY_2KHZ); // Initialize the buzzer at 2kHz
    BEEP_Cmd(ENABLE); // Enable the buzzer
    enableInterrupts(); // Enable interrupts

    while (1)
    {
        // Main loop - insert additional code here if needed
    }
}

/* Buzzer Initialization Function */
void HalBeep_Init(BEEP_Frequency_TypeDef beep_fre)
{
    BEEP_DeInit(); // Reset the BEEP registers to their default values
    BEEP_Init(beep_fre); // Initialize the BEEP with the specified frequency
}

Programming and Configuring the PD4 beeper Function

Flash the Program using ST-Link and STVP Software:
- Use the ST-Link programmer and the official STVP software to flash the hex file onto the microcontroller.
Steps for Flashing and Configuration in STVP:
- Step 1: Open the STVP software, select the “PROGRAM MEMORY” option, go to File -> Open, and locate the saved hex file.
- Step 2: Select the “OPTION BYTE” option and modify the AFR7 bit to enable the alternate function for PD4.
- Step 3: In the software menu, go to Program -> All Tabs to flash both the program and option bytes.

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