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There are altogether 5 ADC sampling channels in STM8S003, from AIN2 to AIN6. When multi-channel sampling, the ADC conversion mode needs to be set to single conversion mode. After each switchover of sampling channels, the ADC needs to be re-initialized, and the sampling results are read in interrupt.
I/O port initialization code
//AD channel pin initialization
void ADC_GPIO_Init( void )
{
PD_DDR &= ~( 1 << 2 ); // set PD2 to input AIN3
PD_CR1 &= ~( 1 << 2 ); //PD2 is set to dangling input
PD_DDR &= ~( 1 << 3 ); //PD3 is set to input AIN4
PD_CR1 &= ~( 1 << 3 ); //PD3 is set to dangling input
PC_DDR &= ~( 1 << 4 ); //PC4 is set to input AIN2
PC_CR1 &= ~( 1 << 4 ); //PC4 is set to dangling input
PD_DDR &= ~( 1 << 5 ); //PD5 is set to input AIN5
PD_CR1 &= ~( 1 << 5 ); //PD5 is set to dangling input
PD_DDR &= ~( 1 << 6 ); //PD6 is set to input AIN6
PD_CR1 &= ~( 1 << 6 ); //PD6 is set to dangling input
}
Copy the code
Set the I/O ports of the ADC to input mode.
Next, initialize the ADC functionality
void ADC_CH_Init( u8 ch )
{
char l = 0;
ADC_CR1 = 0x00; //fADC = fMASTER/2, 8Mhz single conversion, disable conversion
ADC_CSR = ch + 1; // Control the status register to select the desired AD input channel such as: PD2(AIN3)
ADC_CR2 = 0x00; // By default, the data is read high first and read low first
ADC_TDRL = ( 1 << ( ch + 1));// Disable the corresponding channel schmidt trigger function 1 to shift the left ch+1 bit
ADC_CR1 |= 0x01; // Enable ADC and start conversion
ADC_CSR |= 0x20; //EOCIE Enables conversion end interrupt Enables EOC interrupt
for( l = 0; l < 100; l++ ); // Delay to ensure that the ADC module is powered on for at least 7us
ADC_CR1 = ADC_CR1 | 0x01; // Enable ADC in the lowest position 1 of register CR1 again and start the conversion
}
Copy the codeSet the ADC to a single conversion mode and manually set the lowest position 1 of the CR1 register for each conversion.
Read the data after a successful conversion in an interrupt.
#pragma vector = 24 // Add 2 to the interrupt number in the STVD
__interrupt void ADC_Handle( void )
{
ADC_CSR &= ~0x80; // Clear the end of conversion flag EOC
// By default, the high 8 bits are read before the low 8 bits are read
DATAH = ADC_DRH; // Read the top 8 bits of the ADC result
DATAL = ADC_DRL; // Read the lower 8 bits of the ADC result
ADC_flag = 1; // Set the ADC interrupt flag to 1
}
Copy the codeIn interrupt, the converted sample value is stored in the DATAH and DATAL, and the sampling end flag bit ADC_flag is set. When the sampling function determines that the flag bit is 1, it reads the ADC sample value.
Sample value read function:
// Collect the voltage of PC4, AIN2
u16 ReadVol_CH2( void )
{
u16 voltage = 0;
ADC_CH_Init( 1 );
while( ADC_flag == 0 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ; // Obtain data from 0 to 1024
//ADC_CR1 = ADC_CR1 | 0x01; // Start the next conversion again with the lowest position 1 of the CR1 register
};
return voltage;
}
Copy the codeThe functions of some pins of MCU need to be opened by option word. The method of setting option word by ST Visual Programmer software is as follows:
In AFR7, set PC4 to the AIN2 feature in the option word.
The complete code for ADC is as follows:
#include "adc.h"
#include "main.h"
u16 DATAH = 0; // The ADC converts the value 8 bits higher
u16 DATAL = 0; // The ADC converts the value 8 bits lower
_Bool ADC_flag = 0; //ADC conversion success flag
//AD channel pin initialization
void ADC_GPIO_Init( void )
{
PD_DDR &= ~( 1 << 2 ); // set PD2 to input AIN3
PD_CR1 &= ~( 1 << 2 ); //PD2 is set to dangling input
PD_DDR &= ~( 1 << 3 ); //PD3 is set to input AIN4
PD_CR1 &= ~( 1 << 3 ); //PD3 is set to dangling input
PC_DDR &= ~( 1 << 4 ); //PC4 is set to input AIN2
PC_CR1 &= ~( 1 << 4 ); //PC4 is set to dangling input
PD_DDR &= ~( 1 << 5 ); //PD5 is set to input AIN5
PD_CR1 &= ~( 1 << 5 ); //PD5 is set to dangling input
PD_DDR &= ~( 1 << 6 ); //PD6 is set to input AIN6
PD_CR1 &= ~( 1 << 6 ); //PD6 is set to dangling input
}
//ADC input channel initialization entry parameter indicates channel selection
void ADC_CH_Init( u8 ch )
{
char l = 0;
ADC_CR1 = 0x00; //fADC = fMASTER/2, 8Mhz single conversion, disable conversion
ADC_CSR = ch + 1; // Control the status register to select the desired AD input channel such as: PD2(AIN3)
ADC_CR2 = 0x00; // By default, the data is read high first and read low first
ADC_TDRL = ( 1 << ( ch + 1));// Disable the corresponding channel schmidt trigger function 1 to shift the left ch+1 bit
ADC_CR1 |= 0x01; // Enable ADC and start conversion
ADC_CSR |= 0x20; //EOCIE Enables conversion end interrupt Enables EOC interrupt
for( l = 0; l < 100; l++ ); // Delay to ensure that the ADC module is powered on for at least 7us
ADC_CR1 = ADC_CR1 | 0x01; // Enable ADC in the lowest position 1 of register CR1 again and start the conversion
}
// Collect the voltage of PC4, AIN2
u16 ReadVol_CH2( void )
{
u16 voltage = 0;
ADC_CH_Init( 1 );
while( ADC_flag == 0 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ; // Obtain data from 0 to 1024
//ADC_CR1 = ADC_CR1 | 0x01; // Start the next conversion again with the lowest position 1 of the CR1 register
};
return voltage;
}
// Collect the PD2 voltage AIN3
u16 ReadVol_CH3( void )
{
u16 voltage = 0;
ADC_CH_Init( 2 );
while( ADC_flag == 0 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ;
//ADC_CR1 = ADC_CR1 | 0x01; // If the channel does not need to be switched, it only needs to be initialized once. After each time the data is read, the next conversion needs to be manually enabled
};
return voltage;
}
// Collect the PD3 voltage value AIN4
u16 ReadVol_CH4( void )
{
u16 voltage = 0;
ADC_CH_Init( 3 );
while( ADC_flag == 0 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ; // Obtain data from 0 to 1024
//ADC_CR1 = ADC_CR1 | 0x01; // Start the next conversion again with the lowest position 1 of the CR1 register
};
return voltage;
}
// Collect the PD5 voltage value AIN5
u16 ReadVol_CH5( void )
{
u16 voltage = 0;
ADC_CH_Init( 4 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ; // Obtain data from 0 to 1024
//ADC_CR1 = ADC_CR1 | 0x01; // Start the next conversion again with the lowest position 1 of the CR1 register
};
return voltage;
}
// Collect the PD6 voltage value AIN6
u16 ReadVol_CH6( void )
{
u16 voltage = 0;
ADC_CH_Init( 5 );
if( ADC_flag )
{
ADC_flag = 0;
voltage = ( DATAH << 2 ) + DATAL ; // Obtain data from 0 to 1024
//ADC_CR1 = ADC_CR1 | 0x01; // Start the next conversion again with the lowest position 1 of the CR1 register
};
return voltage;
}
//AD interrupt service function interrupt number 22
#pragma vector = 24 // Add 2 to the interrupt number in the STVD
__interrupt void ADC_Handle( void )
{
ADC_CSR &= ~0x80; // Clear the end of conversion flag EOC
// By default, the high 8 bits are read before the low 8 bits are read
DATAH = ADC_DRH; // Read the top 8 bits of the ADC result
DATAL = ADC_DRL; // Read the lower 8 bits of the ADC result
ADC_flag = 1; // Set the ADC interrupt flag to 1
}
Copy the codeThe main function code is as follows:
#include "iostm8s103F3.h"
#include "main.h"
#include "led.h"
#include "adc.h"
#include "delay.h"
u16 val_ch2 = 0, val_ch3 = 0, val_ch4 = 0, val_ch5 = 0, val_ch6 = 0;
void SysClkInit( void )
{
CLK_SWR = 0xe1; //HSI 16MHz CPU clock frequency of the primary clock source
CLK_CKDIVR = 0x00; // The CPU clock is 0 and the system clock is 0
}
void main( void )
{
u8 i=0;
__asm( "sim" ); // Disable interrupt
SysClkInit();
delay_init( 16 );
LED_GPIO_Init();
ADC_GPIO_Init();
__asm( "rim" ); // Enable interrupt
while( 1 )
{
LED = ~LED;
// After the channel switch, the first batch of sampled data is still the data of the previous channel
for(i=0; i<10; i++) val_ch2 = ReadVol_CH2(); delay_ms(100 );
for(i=0; i<10; i++) val_ch3 = ReadVol_CH3(); delay_ms(100 );
for(i=0; i<10; i++) val_ch4 = ReadVol_CH4(); delay_ms(100 );
for(i=0; i<10; i++) val_ch5 = ReadVol_CH5(); delay_ms(100 );
for(i=0; i<10; i++) val_ch6 = ReadVol_CH6(); delay_ms(100); }}Copy the code