Starting STM8 Microcontrollers

STM8S003K3 Discovery

External Interrupt (EXTI)

External interrupt is an additional feature of GPIOs in input mode. It makes a micro to respond instantly to changes done on it GPIO input pin(s) by an external events/triggers, skipping other tasks. External interrupts are useful in many scenarios. For instance, an emergency button. Consider the case of a treadmill. You are running at a speed and suddenly you get an ache in one of your ankles. You’ll surely want to stop running immediately. Rather decreasing speed in small steps, you can hit the emergency button to quickly stop the treadmill. The emergency button will interrupt all other processes and immediately instruct the treadmill’s CPU to decrease speed faster than otherwise possible. Thus, it has high priority over other processes.

In most 8-bit micros, there are few external interrupt pins and very limited options are available for them but that’s not the case with STM’s micros. In STM8s, almost all GPIO pins have independent external interrupt capability with input Schmitt triggers. Additionally, there’s interrupt controller to set interrupt priority.

Schematic

 

Hardware Connection

CubeMX

Code Example

We will do the same variable flash rate LED blinking example as in the GPIO example but this time with the DISCO board’s button in external interrupt mode. The code here needs special attention as now we will see how interrupts are configured and coded. This code is way different than anything I saw before. I’m saying so because you’ll need to follow certain steps unlike other compilers. In other compilers, all we do is create the interrupt function and tell the compiler the interrupt vector address. Same here too but too many steps involved.

Now check the interrupt vector table of STM8S003 below:

Vector Table

You’ll find this table not in the reference manual but in the device’s datasheet. This table varies with devices and so be sure of correct datasheet. The DISCO board’s button is connected to PB7 and so clearly, we will need IRQ4, i.e. EXTI1 or PORTB external interrupts. All external interrupts on GPIOB pin are masked in this vector address.

Please note that codes that use peripheral interrupts need stm8s_it.h and stm8s_it.c files. Therefore, add them if you are to use interrupts.

main.c

#include "stm8s.h"
 
 
bool state = FALSE;
 
 
void GPIO_setup(void);
void EXTI_setup(void);
void clock_setup(void);
 
 
void main(void)
{
    GPIO_setup();
    EXTI_setup();
    clock_setup();
                
    do
    {
         GPIO_WriteReverse(GPIOD, GPIO_PIN_0);
         if(state == TRUE)
         {
               delay_ms(100);
         }
         else
         {
               delay_ms(1000);
         }
    }while (TRUE);
}
 
 
void GPIO_setup(void)
{
    GPIO_DeInit(GPIOB);    
    GPIO_Init(GPIOB, GPIO_PIN_7, GPIO_MODE_IN_PU_IT);
                
    GPIO_DeInit(GPIOD);
    GPIO_Init(GPIOD, GPIO_PIN_0, GPIO_MODE_OUT_PP_LOW_FAST);
}
 
 
void EXTI_setup(void)
{
    ITC_DeInit();
    ITC_SetSoftwarePriority(ITC_IRQ_PORTB, ITC_PRIORITYLEVEL_0);
                
    EXTI_DeInit();
    EXTI_SetExtIntSensitivity(EXTI_PORT_GPIOB, EXTI_SENSITIVITY_FALL_ONLY);
    EXTI_SetTLISensitivity(EXTI_TLISENSITIVITY_FALL_ONLY);
                
    enableInterrupts();
}
 
 
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_HSIDIV1);
    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, DISABLE);
    CLK_PeripheralClockConfig(CLK_PERIPHERAL_TIMER4, DISABLE);
}

 

stm8_interrupt_vector.c

/*              BASIC INTERRUPT VECTOR TABLE FOR STM8 devices
 *              Copyright (c) 2007 STMicroelectronics
 */
 
#include "stm8s_it.h"
 
 
typedef void @far (*interrupt_handler_t)(void);
 
struct interrupt_vector 
{
    unsigned char interrupt_instruction;
    interrupt_handler_t interrupt_handler;
};
 
//@far @interrupt void NonHandledInterrupt (void)
//{
                /* in order to detect unexpected events during development, 
                   it is recommended to set a breakpoint on the following instruction
                */
//              return;
//}
 
extern void _stext();     /* startup routine */
 
 
struct interrupt_vector const _vectab[] = {
                {0x82, (interrupt_handler_t)_stext}, /* reset */
                {0x82, NonHandledInterrupt}, /* trap  */
                {0x82, NonHandledInterrupt}, /* irq0  */
                {0x82, NonHandledInterrupt}, /* irq1  */
                {0x82, NonHandledInterrupt}, /* irq2  */
                {0x82, NonHandledInterrupt}, /* irq3  */
                {0x82, (interrupt_handler_t)EXTI1_IRQHandler}, /* irq4  */
                {0x82, NonHandledInterrupt}, /* irq5  */
                {0x82, NonHandledInterrupt}, /* irq6  */
                {0x82, NonHandledInterrupt}, /* irq7  */
                {0x82, NonHandledInterrupt}, /* irq8  */
                {0x82, NonHandledInterrupt}, /* irq9  */
                {0x82, NonHandledInterrupt}, /* irq10 */
                {0x82, NonHandledInterrupt}, /* irq11 */
                {0x82, NonHandledInterrupt}, /* irq12 */
                {0x82, NonHandledInterrupt}, /* irq13 */
                {0x82, NonHandledInterrupt}, /* irq14 */
                {0x82, NonHandledInterrupt}, /* irq15 */
                {0x82, NonHandledInterrupt}, /* irq16 */
                {0x82, NonHandledInterrupt}, /* irq17 */
                {0x82, NonHandledInterrupt}, /* irq18 */
                {0x82, NonHandledInterrupt}, /* irq19 */
                {0x82, NonHandledInterrupt}, /* irq20 */
                {0x82, NonHandledInterrupt}, /* irq21 */
                {0x82, NonHandledInterrupt}, /* irq22 */
                {0x82, NonHandledInterrupt}, /* irq23 */
                {0x82, NonHandledInterrupt}, /* irq24 */
                {0x82, NonHandledInterrupt}, /* irq25 */
                {0x82, NonHandledInterrupt}, /* irq26 */
                {0x82, NonHandledInterrupt}, /* irq27 */
                {0x82, NonHandledInterrupt}, /* irq28 */
                {0x82, NonHandledInterrupt}, /* irq29 */
};

 

Now check the top parts of the stm8s_it.h and stm8s_it.c files respectively.

stm8s_it.h

stm8s_it.h_file

 

stm8s_it.c

stm8s_it.c_file

These must be coded.

 

Explanation

Most part of the code is same as previous codes and so I won’t be going through them again. However, there’s something new:

void EXTI_setup(void)
{
   ITC_DeInit();
   ITC_SetSoftwarePriority(ITC_IRQ_PORTB, ITC_PRIORITYLEVEL_0);
                
   EXTI_DeInit();
   EXTI_SetExtIntSensitivity(EXTI_PORT_GPIOB, EXTI_SENSITIVITY_FALL_ONLY);
   EXTI_SetTLISensitivity(EXTI_TLISENSITIVITY_FALL_ONLY);
                
   enableInterrupts();
}

This function is where we are setting up the external interrupt. The first two lines deinitiate the interrupt controller and set priority while initiating it. It is not mandatory unless you want to set interrupt priority. Then we configure the external interrupt on PORTB pins. We also set the edge that will invoke an interrupt. Finally, we enable global interrupt. There goes the main.c file

Now it’s time to explain the stm8_interrupt_vector.c file. The top part of this file must include this line #include “stm8s_it.h”. It must also have the following section commented out:

//@far @interrupt void NonHandledInterrupt (void)
//{
                /* in order to detect unexpected events during development, 
                   it is recommended to set a breakpoint on the following instruction
                */
//              return;
//}

We need to let our compiler know the name of the function that it should call when a particular interrupt is triggered. There are two parts for that. Firstly, the interrupt vector address and secondly the name of the function. This is reason for this line:

{0x82, (interrupt_handler_t)EXTI1_IRQHandler}, /* irq4  */

Lastly, the stm8s_it.h and stm8s_it.c files contain the prototype and the function that will execute the interrupt service routine (ISR). In our case, the ISR will change the logic state of the Boolean variable state. This will alter that flashing rate in the main loop.

Demo

Video link: https://www.youtube.com/watch?v=P6qdmWgH-Ls

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40 comments

  • 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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