Starting STM8 Microcontrollers

STM8S003K3 Discovery

Time Base Generation (TIM2)

Time base generation is the most basic property of any timer and is also the most needed requirement in embedded systems. This mode can be used with or without interrupt. We’ll first check the method firstly without interrupt and then with interrupt.

With time base generation, we can accurately time stuffs and events that are more precise than using delays, loops or other methods. Time base generation utilizes hardware timers and so work independently from other processes. It has many uses. For instance, with it we can avoid software delays, generate time slots of a Real-Time Operating System (RTOS) and many other tasks.

Time-Base Unit

The time base unit for all timers of STM8 is all same. There are a few differences. For example, Timer 1 (TIM1) has a repetition counter. It is like a counter within another counter. Other timers lack this part. All timers can count up while advance timers can count down too.

The basic theory of time base generation is you have a peripheral clock which you would like to scale according to your need. Thus, you prescale it and use the new clock to run a counter. The counter will tick, incrementing count as time flies. It is just like counting from 0 to 100 and repeating from 0 again after reaching 100. Shown below is the generalized formula for finding an important event called timer reload:

Formula for TIM base

This is the amount of time that will pass before timer overflow event occurs and the timer restarts from its initial count.

In my example, the peripheral or master clock is set to 2MHz. Thus, to make timer 2 (TIM2) reload after roughly 2 seconds, I have to prescale it by a factor of 2048 and load it with 1952 counts. Note that TIM2 doesn’t have a repetition counter and so it is set to 1.

Hardware Connection

CubeMX

 

Code Example

In this example, Disco board’s user LED is turned-on and off without using any software delay. TIM2 is used to create time delay as such that the code is not stuck in a time-wasting loop.

#include "STM8S.h"
 
 
void clock_setup(void);
void GPIO_setup(void);
void TIM2_setup(void);
 
 
void main(void)
{
    clock_setup();
    GPIO_setup();
    TIM2_setup();
                
    while(TRUE)
    {
          if(TIM2_GetCounter() > 976)
          {
               GPIO_WriteHigh(GPIOD, GPIO_PIN_0);
          }
          else
          {
               GPIO_WriteLow(GPIOD, GPIO_PIN_0);
          }
    };
}
 
 
void clock_setup(void)
{
    CLK_DeInit();
                
    CLK_HSECmd(DISABLE);
    CLK_LSICmd(DISABLE);
    CLK_HSICmd(ENABLE);
    while(CLK_GetFlagStatus(CLK_FLAG_HSIRDY) == FALSE);
                
    CLK_ClockSwitchCmd(ENABLE);
    CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV8);
    CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);
                
    CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSI, 
    DISABLE, CLK_CURRENTCLOCKSTATE_ENABLE);
                
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_SPI, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_I2C, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_ADC, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_AWU, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_UART1, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER1, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER2, ENABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER4, DISABLE);
}
 
 
void GPIO_setup(void)
{
    GPIO_DeInit(GPIOD);
    GPIO_Init(GPIOD, GPIO_PIN_0, GPIO_MODE_OUT_OD_HIZ_SLOW);
}
 
 
void TIM2_setup(void)
{
    IM2_DeInit();
    TIM2_TimeBaseInit(TIM2_PRESCALER_2048, 1952);
    TIM2_Cmd(ENABLE);
}

 

Explanation

Firstly, the CPU and the peripheral clock are both set at 2 MHz.

CLK_HSIPrescalerConfig(CLK_PRESCALER_HSIDIV8);
CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);
….
….
CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER2, ENABLE);

As explained earlier, to get 2 second timer reload interval we need to prescale the timer by 2048 and load its counter with 1952. This is what should be the setup for TIM2:

void TIM2_setup(void)
{
     TIM2_DeInit();
     TIM2_TimeBaseInit(TIM2_PRESCALER_2048, 1952);
     TIM2_Cmd(ENABLE);
}

Our goal is to keep the LED on for 1 second and off for 1 second. It takes 1952 TIM2 counts for 2 second interval and so one second passes when this count is 976. Thus, in the main loop we are checking the value of TIM2’s counter. From 0 to 976 counts, the LED is on and from 977 to 1952 counts, the LED is off. Note that the LED’s positive end is connected to VDD and so it will turn on only PD0 is low.

if(TIM2_GetCounter() > 976)
{
     GPIO_WriteHigh(GPIOD, GPIO_PIN_0);
}
else
{
     GPIO_WriteLow(GPIOD, GPIO_PIN_0);
}

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50 comments

  • Thanks for this article..
    I am looking for microsd card interface with STM8s discovery board. can you please provide the tutorial for microsd card?

  • In relation to disabling unused peripheral clocks as suggested by you:

    I found the following list of peripherals in the STM8S105 Discovery Board: Advanced control timer (TIM1), General-purpose timers (TIM2 and TIM3), Basic timer (TIM4), SPI, I2C, UART2, Window WDG, Independent WDG, ADC1,
    AWU timer, Beeper.

    Is this all?

    I could not find the clock peripheral configuration function for Window WDG, Independent WDG, Beeper in the Standard Peripheral Library.
    Is it not required?

    P.S. I am new to MCU programming with a little experience on Arduino. So please forgive me if the question is foolish.

    • 1. STM8S003K3 Discovery – the one I use for the blog is different from STM8S105…. They have different peripherals and so there will be differences in peripheral clocks…. Please check the device datasheet/STM8CubeMX for available hardware….

      2. WWDG and IWDG are set in option bytes and they don’t use peripheral/CPU clock…. Their oscillator is separate…. Due to these they don’t have clock configurations like other peripherals….

      P.S: No question is a noob question…. every question is allowed no matter how silly it may look….

  • Hi please someone tel me where can i find stm8s_delay.h and stm8s_delay.c
    Thanks

  • Hi , please someone tel me . Where can i find stm8s_delay.h and stm8s_delay.c
    Thanks ..

  • i am using stms003f3p6 controller..i have done as u told exactly but tim1 input capture is not displaying any value …according to your article it should display 10…i dont have any errors everything is fine…pulse on tim2 is ok ..it is coming as u said…but capture not working..please help me …thank you…

  • Hi Sir,
    i have just follwed your instruction provied in yout tutorial in main.c

    #include “stm8s.h”

    main()
    {
    while (1);
    }

    This error comes, can you please check why this error come, i am new and learn the controller programming.

    main.c:
    The command: “cxstm8 -i”d:\other datasheet\new folder\lib\stm8s_stdperiph_lib\libraries\stm8s_stdperiph_driver\inc” +debug -pxp -no -l +mods0 -pp -i”C:\Program Files (x86)\COSMIC\FSE_Compilers\CXSTM8\Hstm8″ -clDebug\ -coDebug\ main.c ” has failed, the returned value is: 1
    exit code=1.

    main.o – 2 error(s), 0 warning(s)

    Thanks,

  • Hi there, i solve the previous ADC problem. Anyway, u make some good tutorial on stm8 chips. Nice work

    • What was causing that issue? How did you solve it?

      • because i put all these

        ADC_DeInit(ADC1);
        ADC_SamplingTimeConfig(ADC1, ADC_Group_SlowChannels, ADC_SamplingTime_4Cycles);
        ADC_SchmittTriggerConfig(ADC1, ADC_Channel_7, DISABLE);
        ADC_ChannelCmd(ADC1, ADC_Channel_7, ENABLE);
        ADC_Init(ADC1, ADC_ConversionMode_Continuous, ADC_Resolution_12Bit, ADC_Prescaler_1);
        ADC_Cmd(ADC1, ENABLE);
        ADC_ExternalTrigConfig(ADC1, ADC_ExtEventSelection_None, ADC_ExtTRGSensitivity_All);

        in ‘while(1)’. It keeps looping.

        Once i put it before ‘while (1)’, it becomes normal.

  • Hi there, thanks for sharing. I learn alot thru your example, but I have encounter a problem with adc. Im currently using stm8l151k4t6. I wanna use the pin D7 as to read the voltage from my battery and monitor it (display on LCD). Can u please check where it goes wrong on my code?

    ADC_DeInit(ADC1);
    ADC_SamplingTimeConfig(ADC1, ADC_Group_SlowChannels, ADC_SamplingTime_4Cycles);
    ADC_SchmittTriggerConfig(ADC1, ADC_Channel_7, DISABLE);
    ADC_ChannelCmd(ADC1, ADC_Channel_7, ENABLE);
    ADC_Init(ADC1, ADC_ConversionMode_Continuous, ADC_Resolution_12Bit, ADC_Prescaler_1);
    ADC_Cmd(ADC1, ENABLE);
    ADC_ExternalTrigConfig(ADC1, ADC_ExtEventSelection_None, ADC_ExtTRGSensitivity_All);
    ADC_SoftwareStartConv(ADC1);
    while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC));
    battery = ADC_GetConversionValue(ADC1);

  • hi shawon great tutorials it would be nice too if you covered the coide compiler for arm it’s a good free compiler

  • hi shawon thanks for your response and support it turns out that my problem was a license issue I stupidly thought i use one license on multiple pc’s I used the license for a particular computer for mine that’s why I’ve been having compilation issues you have to use the license file stm8 sends you that is generated by your own pc else it won’t compile it’ll jus kip throwing you errors

  • It seems that you didn’t follow my instructions completely…. I found some issues:

    1. You have included header and source files of ADC2, CAN, UART2, etc which are unavailable in STM8S103…. Add only files for the peripherals available in your target MCU…. Exclude the rest….

    2. You have not included stm8s_delay header and source files…. Either disable it from stm8s_conf.h header file if you are not going to use it or add both the header and the source files for it in your project….

    Resolve these and you are good to go….

    Thanks….

  • I haven’t compiled any of the examples yet I just tried to compile the main source file just for test purpose n it just keeps showing me the same errors

  • yes the comic compiler was installed properly i even received a license file from my mail with the instructions to copy the license file to the license folder in the install directory if you fail to do this it will keep popping up for you to put in the license file. iincluded all the source files and header files as instructed i am working with the cheap stm8s103f i uncommented the stm8s103f in the stm8.h header file as you instructed and just to compile the main file it just throws me errors

  • no I just followed your instructions I just compiled it after setup i did not write any code yet just compiled the default main file

    • Need more details….

      1. The version of STVD and Cosmic
      2. Which example is giving this issue?
      3. The chip you are using if it other than STM8S003
      4. Have you tried to compile something else other than my examples?
      5. Are the paths to libraries and other folders properly added?
      6. Is the Cosmic compiler registered properly?

  • it throws this line The command: “cxstm8 -iinc +debug -pxp -no -l +mods0 -pp -i”C:\Program Files (x86)\COSMIC\FSE_Compilers\Hstm8″ -clDebug\ -coDebug\ main.c ” has failed, the returned value is: 1
    exit code=1.

  • hi I’m having compilation issues when I compile it just throws me error about comic compiler located in the program file ialso excluded unwanted header files but my problems still weren’t solved

  • hi thanks for the tutorials but i am having compiler error issues even when I remove unnecessary header files it say comic compiler error

  • I am new to STM8S003k3 Discovery board.I have done UART communication using STM standard peripheral library example. Now I want to define any other GPIO pin for UART communication. Is it possible to use d0 and d1 pin for the UART communication? If yes, then please let me know how?

  • thank you very much for this article!

  • Thank you for your time and effort.

  • Good job bro

  • Thank you for this exceptionally comprehensive article, much appreciated

    Rando!

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