Proper way to bit bang with KEIL

Hello, what im trying to do is reverse engineering unknown device. What i need is catch a 16bytes data from it. Each clk's pulse speed is about 20 nanoseconds. I'm using stm32f4 discovery board, so i should be able to catch it as stm32 powerful uC. The fact that im really new in Keil, and i dont know if im doing it a propper way, for example to detect a GPIO goes down, im using this code

 while (HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_7) == 0){}

Is it proper way to do it?
THe whole code with comments are:

  while (1)
                uint8_t collect_bits = 0;
                char string_array[21] = {0};
        //      HAL_Delay(200);
        while (HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_9) == 0){}   // wait until GPIOC 9 goes high
                                                                while (HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_9) == 1){}  // wait until GPIOC 9 goes low
         for (int i = 0; i < 8; i++)      // make a loop for reading byte
                                         while (HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_7) == 0){}     // wait until clock goes high
       int32_t current_bit = HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_9);                       // READ bit on PINC 9
    collect_bits |=  current_bit << i;  // Shift current_bit to position i and
                                        // put it into collect_bits using bit wise OR
                                                         while (HAL_GPIO_ReadPin (GPIOC,GPIO_PIN_7) == 1){}     // wait until clock goes low, then repeat while loop untill we collect 8 bits
                sprintf(string_array, "%X", collect_bits);      // just simple convertation for PC output
                CDC_Transmit_FS((uint8_t*)string_array, sizeof(string_array));   // print result.



  /* USER CODE END 3 */


The problem is that output is not correct.What am i doing wrong? thanks

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