(stm32f100 Discovery) Can I read output GPIO ports?

[Build-A-Burger]

I'm interfacing a 4x4 keypad to an STM32F100 Discovery board - using PC0->3 as the 4 columns and PB12->15 as the rows. The rows are outpus and the columns are inputs. The 4 rows do a scan (each bit goes low one at a time) in one task and when a key is pressed one of the inputs causes an ISR to be triggered. I want to read the current state of the output port (GPIOB) within the ISR so I can do a lookup for the keypad.

Here's my code:

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
	UCHAR crow;
	volatile long unsigned int *regb;
	volatile long unsigned int regb3;
	volatile long unsigned int regb3a;
	unsigned int regb4;
	uint8_t col;
	uint8_t key_pressed;

	regb = (long unsigned int*)GPIOB->ODR;
	regb3 = *regb;
	regb3a = regb3;

	regb4 = (unsigned int)regb3;
	crow = (UCHAR)regb4;

	crow += 0x30;
	HAL_UART_Transmit(&huart2, &crow, 1, 100);

	regb4 = (unsigned int)regb3;
	regb4 >>= 8;
	crow = (UCHAR)regb4;

	crow += 0x30;
	HAL_UART_Transmit(&huart2, &crow, 1, 100);

	regb4 = (unsigned int)regb3;
	regb4 >>= 16;
	crow = (UCHAR)regb4;
	crow += 0x30;
	HAL_UART_Transmit(&huart2, &crow, 1, 100);

	regb4 >>= 8;
	crow = (UCHAR)regb4;
	crow += 0x30;
	HAL_UART_Transmit(&huart2, &crow, 1, 100);

/*
	col = (UCHAR)GPIO_Pin;
	switch(col)
	{
		case 1:
		col = 0;
		break;
		case 2:
		col = 1;
		break;
		case 4:
		col = 2;
		break;
		case 8:
		col = 3;
		break;
		default:
		col = 0;
		break;
	}
 	key_pressed = (au8_keyTable[glrow][col]);
	glrow += 0x30;
	HAL_UART_Transmit(&huart2, &glrow, 1, 100);

	crow = 0x20;
	HAL_UART_Transmit(&huart2, &crow, 1, 100);
 */
	
}

All I get is slashes. There's goto be an easier way to do this other than possible doing a HAL_GPIO_ReadPin(GPIOB, x);
BTW, I'm compiling with Atollic TrueStudio and using FreeRTOS.

 

[Build-A-Burger]

OK - I've got it working now without using an ISR:

void StartKeyPressed(void const * argument)
{
	/* USER CODE BEGIN StartKeyPressed */
//	unsigned long ulReceivedValue;
	uint8_t u8_row;
	uint8_t key_pressed;
	GPIO_PinState state;

	key_pressed = 0;

	/* Infinite loop */
	for(;;)
	{
		key_pressed = 0;
  		for (u8_row = 0; u8_row < NUM_ROWS; u8_row++)
		{
			setOneRowLow(u8_row);
			vTaskDelay(1);
			state = HAL_GPIO_ReadPin(GPIOC,col0);
			if(state == GPIO_PIN_RESET)
			{
			 	key_pressed = (au8_keyTable[u8_row][0]);
				HAL_UART_Transmit(&huart2, &key_pressed, 1, 100);
				vTaskDelay(1);
			}
			state = HAL_GPIO_ReadPin(GPIOC,col1);
			if(state == GPIO_PIN_RESET)
			{
			 	key_pressed = (au8_keyTable[u8_row][1]);
				HAL_UART_Transmit(&huart2, &key_pressed, 1, 100);
				vTaskDelay(1);
			}
			state = HAL_GPIO_ReadPin(GPIOC,col2);
			if(state == GPIO_PIN_RESET)
			{
			 	key_pressed = (au8_keyTable[u8_row][2]);
				HAL_UART_Transmit(&huart2, &key_pressed, 1, 100);
				vTaskDelay(1);
			}
			state = HAL_GPIO_ReadPin(GPIOC,col3);
			if(state == GPIO_PIN_RESET)
			{
			 	key_pressed = (au8_keyTable[u8_row][3]);
				HAL_UART_Transmit(&huart2, &key_pressed, 1, 100);
				vTaskDelay(1);
			}
			drive_row_high();
		}
	}
  /* USER CODE END StartKeyPressed */
}

 

[KlausST]

Hi,

What about setting up a timer interrupt every 5ms.
In the according ISR:
* read in ports
* activate new row
* decode the input

With this... the ports have about 5ms to settle
And all keys are processed within 4 x 5ms = 20ms.

Klaus