Starting STM8 Microcontrollers

STM8S003K3 Discovery

Window Watchdog (WWDG)

The WWDG is a bit more advanced watchdog timer. Unlike the IWDG, it will trigger a reset condition if its counter is reloaded earlier or later than a predefined time window. This kind of timer is usually found in high-end microcontrollers like ARMs, ATXMegas and recently released micros. Cool features like this and others make me feel that indeed STM8s are high-end affordable 8-bit alternatives when compared to traditional 8-bit MCUs.

Block Diagram

The WWDG works by comparing a down counter against a window register. The counter can only be refreshed when its value is greater than 0x3F and less than window register value. If the counter is refreshed before the value set on window register or when the counter is less than or equal to 0x3F. If the counter hits the value 0x3F, reset automatically triggers. It is programmer’s responsibility to refresh the counter at proper time. Note unlike IWDG, WWDG is not independent of main clock.

Timing

Formula


Hardware Connection

CubeMX

 

Code Example

The code example here demonstrates WWDG action. Simply Disco board’s user LED and button are used. When the code starts executing, the LED starts blinking slowly, indicating the start of the code. When the code executes the main loop, the LED blinks rapidly to indicate main loop execution. If the button is pressed randomly the micro is reset because the counter is refreshed before the allowed time. Sometimes the micro may not reset because the counter may be in the allowed window – hence the name Window Watchdog.

#include "STM8S.h"
 
 
void clock_setup(void);
void GPIO_setup(void);
void WWDG_setup(void);
 
 
void main(void)
{
    unsigned char i = 0x00;
                
    clock_setup();
    GPIO_setup();
                
    for(i = 0x00; i < 0x04; i++)
    {
         GPIO_WriteReverse(GPIOD, GPIO_PIN_0);
         delay_ms(40);
    }
                
    WWDG_setup();       
                
    while(TRUE)
    {
          if((GPIO_ReadInputPin(GPIOB, GPIO_PIN_7) == FALSE) || 
             ((WWDG_GetCounter() > 0x60) &&    (WWDG_GetCounter() < 0x7F)))
          {
               WWDG_SetCounter(0x7F);
          }
          GPIO_WriteReverse(GPIOD, GPIO_PIN_0);
          delay_ms(20);
     };
}
 
 
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_CPUDIV64);
                
     CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSI, 
     DISABLE, CLK_CURRENTCLOCKSTATE_ENABLE);
                
     CLK_PeripheralClockConfig(CLK_PERIPHERAL_I2C, DISABLE);
     CLK_PeripheralClockConfig(CLK_PERIPHERAL_SPI, 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, DISABLE);
     CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER4, DISABLE);
}
 
 
void GPIO_setup(void)
{                               
     GPIO_DeInit(GPIOB);
     GPIO_Init(GPIOB, GPIO_PIN_7, GPIO_MODE_IN_PU_NO_IT);
                
     GPIO_DeInit(GPIOD);
     GPIO_Init(GPIOD, GPIO_PIN_0, GPIO_MODE_OUT_OD_HIZ_FAST);
}
 
 
void WWDG_setup(void)
{
     WWDG_Init(0x7F, 0x60);
}

 

Explanation

There’s no way to enable watchdogs manually in software as they are always enabled. However, there are configuration bits to select if the IWDG and the WWDG are enabled in software or hardware. They only come in effect when configured. This is cool.

WDG Configuration Bits

For WWDG, we just need to set the value of the down counter and the window register value only.

void WWDG_setup(void)
{
     WWDG_Init(0x7F, 0x60);
}

We need to monitor the WWDG in order to reload it when it is the right time window.

while(TRUE)
{
      if((GPIO_ReadInputPin(GPIOB, GPIO_PIN_7) == FALSE) || 
      ((WWDG_GetCounter() > 0x60) &&    (WWDG_GetCounter() < 0x7F)))
      {
           WWDG_SetCounter(0x7F);
      }
      GPIO_WriteReverse(GPIOD, GPIO_PIN_0);
      delay_ms(20);
};

Remember too early or too late will reset the micro.

 

Demo

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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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