Stm8 MCU ADC sampling function is triggered by timer

   In the use of STM8 Single chip microcomputer ADC When the function , Read ADC There are generally two ways to generate data , One is to constantly read the sampling flag bit , To judge ADC Whether the sampling is over , One is to inform the system whether the sampling is finished by interrupting .

   Sometimes sampling ADC Data time , At certain intervals , Fixed point desampling data . The general way to use it is to use a timer , Then read in the timer interrupt function ADC Sampled data . But the sampling time in this way is not fixed , For example, after entering the timer interrupt ,ADC Sampling has just ended , You can directly use the currently sampled data . But if you're unlucky , After entering the timed interrupt ,ADC Sampling has just begun , Then we need to wait until ADC After sampling , To use data . This will cause each read ADC There will be a random period of data waiting for ADC Data delay .

   General reference STM8 SCM manual found ,ADC Sampling can be triggered by a timer .

   It's triggered by a timer ADC When sampling , The timing time of the timer is fixed , The sampling time is also fixed , In this way, the interval of sampling data is fixed . This is triggered by a timer ADC The sampling time of , Each read can be completely guaranteed ADC The time interval of sampling data is the same , Thus, the error of data is avoided .

   Data manual for open ADC The trigger function is described as follows ：

   For how to set... Through code ADC Trigger , There is no official explanation , There are no relevant routines found on the Internet . So I can only grope by myself , Fortunately, through my own exploration , Pass the timer successfully TRGO The event triggered ADC Start of .

   About ADC Setting of related registers , Basically, it's what I said above 6 strip . Next, you need to set the relevant registers of the timer .

   The timer only needs to be set CR2 In register MMS Just a bit .

   Next, it is implemented through code .

#include "adc.h"
#include "main.h"
#include "led.h"

u16  DATAH = 0;                          //ADC High conversion value 8 position 
u16  DATAL = 0;                          //ADC The conversion value is low 8 position 
_Bool ADC_flag = 0;                      //ADC Conversion success flag 

u16 adc_cnt = 0;
//AD Channel pin initialization 
void ADC_GPIO_Init( void )
{
    
    PD_DDR &= ~( 1 << 2 );              //PD2  Set to input  
    PD_CR1 &= ~( 1 << 2 );              //PD2  Set as dangling input 
    PD_DDR &= ~( 1 << 3 );              //PD3  Set to input  
    PD_CR1 &= ~( 1 << 3 );              //PD3  Set as dangling input 
}
//ch  For the MCU ADC  passageway 
//ADC Enter the channel initialization entry parameter to indicate the channel selection 
void ADC_CH_Init( u8 ch )
{
    
    char l = 0;
    ADC_CR1  = 0x00;                    //fADC = fMASTER/2, 8Mhz  Single conversion , Prohibit conversion 
    ADC_CR2  = 0x00;                    // Default left alignment   When reading data, first read high and then low 
    
    ADC_CR2 |= ( 1 << 6 );              // External trigger enable 

    ADC_CSR  |= ch;                     // Control status register   Choose to  AD Input channel   Such as ：PD2(AIN3)
    ADC_TDRL = ( 1 << ch  );            // Prohibit the corresponding channel   Schmidt trigger function  1 Move left ch position 
    ADC_CR1 |= 0x01;                    // Can make ADC And start to switch 
    ADC_CSR |= ( 1 << 5 );              //EOCIE  Enable conversion end interrupt  EOC Interrupt enable 
    for( l = 0; l < 100; l++ );         // Time delay , Guarantee ADC The power on of the module is completed   At least 7us
    ADC_CR1 = ADC_CR1 | 0x01;           // Once again CR1 The lowest position of the register １  Can make ADC  And start to switch 
}

u16 value = 0;
//AD Interrupt service function   Interrupt number 22
#pragma vector = 24 // IAR Interrupt number in , To be in STVD Add... To the interrupt number in 2
__interrupt void ADC_Handle( void )
{
    
    ADC_CSR &= ~0x80;                            //  The conversion end flag bit is cleared  EOC
    // Default left alignment   When reading data, read high first 8 position   Reread low 8 position 
    DATAH = ADC_DRH;                             //  read out ADC The result is high 8 position 
    DATAL = ADC_DRL;                             //  read out ADC The results are low 8 position 
    ADC_flag = 1;                                // ADC Interrupt flag   Set up 1
    value = ( DATAH << 2 ) + DATAL ; // Get ten bit accuracy data  0--1024
    adc_cnt++;
    LED = !LED;
}

   stay ADC In the code , Compared with ordinary ADC Initialization mode , There is only one more sentence to add here ADC_CR2 Register settings .

ADC_CR2 |= ( 1 << 6 ); // External trigger enable

   stay ADC_CR2 In the register Enable the external trigger conversion function , Set the external trigger event to Internal timer 1 TRG event .

   here ADC The single trigger mode is used , Turn on the external trigger function , Turn on ADC Conversion interrupted , When ADC After the conversion is complete , It will enter into ADC In interruption , Read the sampled data in the interrupt , Then flip LED The state of , Observe with an oscilloscope LED Change of pin level , We can know ADC Interrupt the frequency of entry .

   Next, write the timer initialization code .

unsigned long time_cnt = 0;
//  Use   Timer triggered  ADC sampling 
void tim1_init( void )
{
    
    TIM1_ARRH = ( unsigned char )( 1000 >> 8 );         // timing 1ms
    TIM1_ARRL = ( unsigned char )( 1000 );
    TIM1_PSCRH = ( unsigned char )( 0x0F >> 8 );        // 16M / (1+15) =1M
    TIM1_PSCRL = ( unsigned char )( 0x0F );
    TIM1_RCR = 0x00;                                    // Repeat counter value 
    TIM1_SR1 = ( ~0x01 );                       		// Clear update interrupt flag 

    TIM1_CR2 |= ( 2 << 4 );                             // Enable signal , Used to trigger the output (TRGO)
    
    TIM1_CR1 |= 0x01;                                   // Enable counter 
    TIM1_IER |= 0x01;                           		// Update interrupt enable 
}

#pragma vector = 13 //IAR Interrupt number in , To be in STVD Add... To the interrupt number in 2
__interrupt void Timer1_Handle( void )         			//1ms  Timed interrupt 
{
    
    TIM1_SR1 = ( ~0x01 );                        		// Clear update interrupt flag 
    time_cnt++;
}

   Timer initialization code , There is also one more line of initialization code than normal .

TIM1_CR2 |= ( 2 << 4 ); // Enable signal , Used to trigger the output (TRGO)

   Used to turn on the timer TRG function .

   After testing , Here's the timer CR2 Value in register Can only be set to 010 perhaps 011, When set to other values , Can't trigger ADC sampling . At the beginning of the test, follow the instructions on the chip data ,MMS The value of is set to 001,ADC It can't be triggered , I thought it was a question of method , It turned out to be MMS Value setting problem .

  ADC And after the timer initialization code is set , Next, initialize these two functions in the main function , According to the information , First initialize ADC after , Then initialize the timer .

void main( void )
{
    

    __asm( "sim" );                             // No interruptions 
    SysClkInit();
    delay_init( 16 );
    LED_GPIO_Init();
     ADC_GPIO_Init();
    ADC_CH_Init(3);
    tim1_init();
    __asm( "rim" );                             // Open interrupt 
    while( 1 )
    {
    
       
    }
}

   Next, run the program .

   Respectively in ADC Interrupt and timer interrupt use a variable to count the number of interrupt execution , You can see... Through the variable observation window ,ADC The number of interrupts is more than that of the timer 1 Time . This is because ADC At initialization time , It has been run once .
   Then observe with an oscilloscope LED The level of the port .

   The timing time of the timer is 1ms,LED The high and low level time is also 1ms, Description triggered by timer ADC The sampling function works normally .
   To reduce the number of system entry interrupts , The interrupt function of the timer can be turned off . After the timer interrupt function is turned off ,ADC The trigger function of can still be used normally .

   You only need to open one ADC interrupt , Plus the timer TRG After triggering the function , Can be realized ADC Timing sampling function .