[SOLVED] PWM signal duty cycle measurement with Capture module

[Knife]

Hi everybody

I wanna measure PWM signal duty cycle with STM8S Capture Module. PWM signal duty is changing between 0% and 100%. System start 0%, 100% or any value between 0% and 100%.

I'm using capture interrupt and I'm measuring exact value of PWM duty. But I have a problem. If the system will start at 0% or %100, I can't handle that value. Because there isn't any changes of signal edge.

I have an idea. I can use one extra I/O port to control signal level. But I wanna ask you first, is there any software solution without using I/O pin ? Could we know capture pin level (high or low) ?

 

[FvM]

Assigning an alternate function to a pin (e.g. input capture) still allows you to read the input state through IDR, isn't it?

 

[Knife]

I haven't solved this problem yet. I tired to read IDR state before I asked here.

I used GPIO_ReadInputPin function. I used TIM1 Channel 1 so it is PC1 pin. GPIO_ReadInputPin(GPIOC, GPIO_PIN_1) function returns 0 when the PWM signal is 0% and 0x02 when the PWM signal is 100%. It should be 1 when the PWM signal is 100%, doesn't it ?

BitStatus GPIO_ReadInputPin(GPIO_TypeDef* GPIOx, GPIO_Pin_TypeDef GPIO_Pin)
{
    return ((BitStatus)(GPIOx->IDR & (uint8_t)GPIO_Pin));
}

 

[FvM]

It should be 1 when the PWM signal is 100%, doesn't it ?

Hardly. 0x2 sounds pretty good. The function does a bitwise and.

 

[Knife]

First of all, thanks for your help. Yes, you are right. I figured out now. I was wrong because I used this code to check capture pin and It didn't work.

typedef enum {RESET = 0, SET = !RESET} FlagStatus, ITStatus, BitStatus, BitAction;

if(GPIO_ReadInputPin(GPIOC, GPIO_PIN_1) == SET)
PWM = 0xFFFF;

I changed the code this one and it works. I'm confiused because I think it is same.

if(GPIO_ReadInputPin(GPIOC, GPIO_PIN_1) != 0)
PWM = 0xFFFF;