Does the PicSimLab BluePill timer support channel 3 and channel 4 for TIM2?

[NCHU-Jimmy]

Hello, I am a beginner in embedded systems.
I am using PlatformIO and PicSimLab with a BluePill to implement a timer output.
I’d like to know if there’s an issue with my code, or if CH3 and CH4 are simply not supported?

This is the code and result for using CH2, and you can see that it works correctly.
(But the output is 5 kHz; it should be 10 kHz instead, right?)

#include <stm32f10x.h>
int main()
{
    RCC->APB2ENR =0b100;
    RCC->APB1ENR =0b1;

    GPIOA->CRL = 0xB0;  
 
    TIM2->CCER = 0x10;   
    TIM2->ARR = 7200 - 1;          
    TIM2->CCR2 = 3000;              
    TIM2->CCMR1 = 0x3000;          
    TIM2->CR1 = 1;       

    while (1)
    {

    }
}

This is the code and result for using CH3, and you can see that it is not working correctly.

#include <stm32f10x.h>
int main()
{
    RCC->APB2ENR =0b100;
    RCC->APB1ENR =0b1;

    GPIOA->CRL = 0xB00;  
 
    TIM2->CCER = 0x1 << 8;   
    TIM2->ARR = 7200 - 1;          
    TIM2->CCR3 = 3000;              
    TIM2->CCMR2 = 0x0030;          
    TIM2->CR1 = 1;       

    while (1)
    {

    }
}

[lcgamboa]

Hi @NCHU-Jimmy ,
There is no problem with your code.
The PWM outputs of qemu-stm32 are fixed at 5KHz for now, it is on the to-do list to implement PWM frequency change support.
Regarding CH3 output, you found a bug in the PICSimLab implementation. The serial port device overlaps the PWM output in pin PA2. I have already detected the problem, and as soon as it is fixed, I will let you know.

[NCHU-Jimmy]

Thank you for your answer!
I also want to confirm two things:
USART3 seems to not be working.
The TIMER's CCIF flag register seems to not be working.
If you need my test program, I can open a new discussion for you later.

[lcgamboa]

Hi @NCHU-Jimmy ,

I fixed the problem with the timer output pins, you can test with the fixed code.
The UART3 is not implemented yet.
As for the other problem with the timer, I would appreciate it if you had a code to demonstrate the error.

[NCHU-Jimmy]

Thank you for fixing the timer output pins!
The following code uses the CC3IF flag to check if PA2 (CH3) has changed, and if there is a change, it displays the current timer value. However, when I change the state of PA2 through PinViewer, it seems that CC3IF cannot capture the change(CC3IF is always 0).

#include <stm32f10x.h>
#include <stdio.h>

void usart1_init(void);
void usart1_sendByte(unsigned char c);
void usart1_sendInt(unsigned int i);
void usart1_sendStr(char *str);
void int_to_str(unsigned int num, char *str);

int main()
{
    RCC->APB2ENR |= (0xFC | (1 << 14)); /* enable GPIO clocks and USART1 clock */
    RCC->APB1ENR |= (1 << 0);           /* enable TIM2 clock */
    usart1_init();
    GPIOA->CRL = 0x44444844;            /* PA2 (CH3): input pull-up */
    GPIOA->ODR |= (1 << 2);

    TIM2->CCMR2 = 0x001;                 /* Pin TIM2_CH3 as input for channel 3 */
    TIM2->CCER = 0x1 << 8;              /* CC3P = 0 (rising), CC3E = 1 */
    TIM2->PSC = 7200 - 1;
    TIM2->ARR = 50000 - 1;
    TIM2->CR1 = 1;                      /* start counting up */
    uint16_t t = 0, t0 = 0;

    while ((TIM2->SR & (1 << 3)) == 0)  /* wait until the CC3IF flag sets */
    t = TIM2->CCR3;                 /* read th captured value */
    usart1_sendInt(t - t0);             /* send the difference */
    usart1_sendStr("\n\r");             /* go to new line */
    TIM2->SR &= ~(0 << 3);              /* clear CC3IF flag */
}

void usart1_init()
{
    GPIOA->ODR |= (1 << 10);            // pull-up PA10
    GPIOA->CRH = 0x444448B4;            // RX1=input with pull-up, TX1=alt. func output
    USART1->CR1 = 0x200C;
    USART1->BRR = 7500;                 // 72MHz/9600bps = 7500
}

void usart1_sendByte(unsigned char c)
{
    USART1->DR = c;
    while ((USART1->SR & (1 << 6)) == 0); // wait until the TC flag is set

}

/* The function sends a zero-ending string through USART1 */
void usart1_sendStr(char *str)
{
    while (*str != 0)
    {
        usart1_sendByte(*str);
        str++;
    }
}

/* The function sends a number through USART1 */
void usart1_sendInt(unsigned int i)
{
    char str[10];
    int_to_str(i, str); // Convert integer to string without using sprintf
    usart1_sendStr(str); // Send the string
}

/* Integer to string conversion (without using sprintf) */
void int_to_str(unsigned int num, char *str)
{
    int i = 0;
    if (num == 0)
    {
        str[i++] = '0';
    }
    else
    {
        int temp = num;
        while (temp > 0)
        {
            str[i++] = (temp % 10) + '0'; // Convert digit to character
            temp /= 10;
        }
        str[i] = '\0';  // Null-terminate the string

        // Reverse the string
        int j = 0;
        char temp_char;
        while (j < i / 2)
        {
            temp_char = str[j];
            str[j] = str[i - j - 1];
            str[i - j - 1] = temp_char;
            j++;
        }
    }
}