#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stm32c0xx_hal.h>

// Keypad connections
#define ROWS 4
#define COLS 4

 
GPIO_TypeDef* row_ports[ROWS] = {GPIOA, GPIOA, GPIOA, GPIOA};
uint16_t row_pins[ROWS] = {GPIO_PIN_0, GPIO_PIN_1, GPIO_PIN_2, GPIO_PIN_3};
GPIO_TypeDef* col_ports[COLS] = {GPIOA, GPIOA, GPIOA, GPIOA};
uint16_t col_pins[COLS] = {GPIO_PIN_4, GPIO_PIN_5, GPIO_PIN_6, GPIO_PIN_7};

// Define the keypad layout (customize as needed)
char keypad[ROWS][COLS] = {
    {'1', '2', '3', 'A'},
    {'4', '5', '6', 'B'},
    {'7', '8', '9', 'C'},
    {'*', '0', '#', 'D'}
};


void scanKeypad(void)
{
    for (int i = 0; i < ROWS; i++)
    {
        // Set the i-th row as output low
        HAL_GPIO_WritePin(row_ports[i], row_pins[i], GPIO_PIN_RESET);
        for (int j = 0; j < COLS; j++)
        {
            // Check if the j-th column reads low, indicating a key press
            if (HAL_GPIO_ReadPin(col_ports[j], col_pins[j]) == GPIO_PIN_RESET)
            {
                // Send the key value via UART
                char key = keypad[i][j];
                HAL_UART_Transmit(&huart2, (uint8_t*)&key, 1, HAL_MAX_DELAY);
            }
        }
        // Restore the i-th row as input with pull-up
        HAL_GPIO_WritePin(row_ports[i], row_pins[i], GPIO_PIN_SET);
    }
}

UART_HandleTypeDef huart2;

void SystemClock_Config(void);
static void MX_USART2_UART_Init(void);

void initGPIO()
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  GPIO_InitStruct.Pin = row_pins[0] | row_pins[1] | row_pins[2] | row_pins[3];
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(row_ports[0], &GPIO_InitStruct);
  HAL_GPIO_Init(row_ports[1], &GPIO_InitStruct);
  HAL_GPIO_Init(row_ports[2], &GPIO_InitStruct);
  HAL_GPIO_Init(row_ports[3], &GPIO_InitStruct);
  
  GPIO_InitStruct.Pin = col_pins[0] | col_pins[1] | col_pins[2] | col_pins[3];
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(col_ports[0], &GPIO_InitStruct);
  HAL_GPIO_Init(col_ports[1], &GPIO_InitStruct);
  HAL_GPIO_Init(col_ports[2], &GPIO_InitStruct);
  HAL_GPIO_Init(col_ports[3], &GPIO_InitStruct);

  __HAL_RCC_GPIOA_CLK_ENABLE();
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();

  initGPIO();
  MX_USART2_UART_Init();

    while (1)
    {
      scanKeypad();  
    }

  return 0;
}

/**
    @brief System Clock Configuration
    @retval None
*/
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Initializes the RCC Oscillators according to the specified parameters
    in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV1;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                                | RCC_CLOCKTYPE_PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
  RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV1;
}

static void MX_USART2_UART_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  __HAL_RCC_GPIOA_CLK_ENABLE();
  // PA2     ------> USART2_TX
  // PA3     ------> USART2_RX
  GPIO_InitStruct.Pin = GPIO_PIN_2|GPIO_PIN_3;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF1_USART2;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
  
  huart2.Instance = USART2;
  huart2.Init.BaudRate = 115200;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  huart2.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
  huart2.Init.ClockPrescaler = UART_PRESCALER_DIV1;
  huart2.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
}

// The following makes printf() write to USART2:

#define STDOUT_FILENO   1
#define STDERR_FILENO   2
int _write(int file, uint8_t *ptr, int len)
{
  switch (file)
  {
    case STDOUT_FILENO:
      HAL_UART_Transmit(&huart2, ptr, len, HAL_MAX_DELAY);
      break;

    case STDERR_FILENO:
      HAL_UART_Transmit(&huart2, ptr, len, HAL_MAX_DELAY);
      break;

    default:
      return -1;
  }

  return len;
}