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// #################################################################################################

// # << NEORV32 - TWI Bus Explorer Demo Program >>                                                 #

// # ********************************************************************************************* #

// # BSD 3-Clause License                                                                          #

// #                                                                                               #

// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #

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// # The NEORV32 Processor - https://github.com/stnolting/neorv32              (c) Stephan Nolting #

// #################################################################################################

/**********************************************************************//**

 * @file demo_twi/main.c

 * @author Stephan Nolting

 * @brief TWI bus explorer.

 **************************************************************************/

#include <neorv32.h>

/**********************************************************************//**

 * @name User configuration

 **************************************************************************/

/**@{*/

/** UART BAUD rate */

#define BAUD_RATE 19200

/**@}*/

// Prototypes

void scan_twi(void);

void set_speed(void);

void send_twi(void);

uint32_t hexstr_to_uint(char *buffer, uint8_t length);

/**********************************************************************//**

 * This program generates a simple dimming sequence for PWM channel 0,1,2.

 *

 * @note This program requires the UART and the TWI to be synthesized.

 *

 * @return Irrelevant.

 **************************************************************************/

int main() {

  char buffer[8];

  int length = 0;

  int bus_claimed = 0;

  // check if UART unit is implemented at all

  if (neorv32_uart_available() == 0) {

    return 0;

  }

  // capture all exceptions and give debug info via UART

  // this is not required, but keeps us safe

  neorv32_rte_enable_debug_mode();

  // init UART at default baud rate, no rx interrupt, no tx interrupt

  neorv32_uart_setup(BAUD_RATE, 0, 0);

  // intro

  neorv32_uart_printf("\n--- TWI Bus Explorer ---\n\n");

  // check if TWI unit is implemented at all

  if (neorv32_twi_available() == 0) {

    neorv32_uart_printf("No TWI unit implemented.");

    return 0;

  }

  // info

  neorv32_uart_printf("This program allows to create TWI transfers by hand.\n"

                      "Type 'help' to see the help menu.\n\n");

  // configure TWI, second slowest clock, no IRQ

  neorv32_twi_setup(CLK_PRSC_2048, 0);

  // no active bus session yet

  bus_claimed = 0;

  // Main menu

  for (;;) {

    neorv32_uart_printf("TWI_EXPLORER:> ");

    length = neorv32_uart_scan(buffer, 8, 1);

    neorv32_uart_printf("\n");

    if (!length) // nothing to be done

     continue;

    // decode input and execute command

    if (!strcmp(buffer, "help")) {

      neorv32_uart_printf("Available commands:\n"

                          " help  - show this text\n"

                          " scan  - scan bus for devices\n"

                          " start - generate START condition\n"

                          " stop  - generate STOP condition\n"

                          " send  - write & read single byte to/from bus\n"

                          " speed - select bus clock\n"

                          "Start a new transmission by generating a START condition. Next, transfer the 7-bit device address\n"

                          "and the R/W flag. After that, transfer your data to be written or send a 0xFF if you want to read\n"

                          "data from the bus. Finish the transmission by generating a STOP condition.\n\n");

    }

    else if (!strcmp(buffer, "start")) {

      neorv32_twi_generate_start(); // generate START condition

      bus_claimed = 1;

    }

    else if (!strcmp(buffer, "stop")) {

      if (bus_claimed == 0) {

        neorv32_uart_printf("No active I2C transmission.\n");

        continue;

      }

      neorv32_twi_generate_stop(); // generate STOP condition

      bus_claimed = 0;

    }

    else if (!strcmp(buffer, "scan")) {

      scan_twi();

    }

    else if (!strcmp(buffer, "speed")) {

      set_speed();

    }

    else if (!strcmp(buffer, "send")) {

      if (bus_claimed == 0) {

        neorv32_uart_printf("No active I2C transmission. Generate a START condition first.\n");

        continue;

      }

      else {

        send_twi();

      }

    }

    else {

      neorv32_uart_printf("Invalid command. Type 'help' to see all commands.\n");

    }

  }

  return 0;

}

/**********************************************************************//**

 * TWI clock speed menu

 **************************************************************************/

void set_speed(void) {

  char terminal_buffer[2];

  neorv32_uart_printf("Select new clock prescaler (0..7): ");

  neorv32_uart_scan(terminal_buffer, 2, 1); // 1 hex char plus '\0'

  uint8_t prsc = (uint8_t)hexstr_to_uint(terminal_buffer, strlen(terminal_buffer));

  if ((prsc >= 0) && (prsc < 8)) { // valid?

    TWI_CT = 0; // reset

    TWI_CT = (1 << TWI_CT_EN) | (prsc << TWI_CT_PRSC0);

    neorv32_uart_printf("\nDone.\n");

  }

  else {

    neorv32_uart_printf("\nInvalid selection!\n");

    return;

  }

  // print new clock frequency

  uint32_t clock = neorv32_cpu_csr_read(CSR_MCLOCK);

  switch (prsc) {

    case 0: clock = clock / 2; break;

    case 1: clock = clock / 4; break;

    case 2: clock = clock / 8; break;

    case 3: clock = clock / 64; break;

    case 4: clock = clock / 128; break;

    case 5: clock = clock / 1024; break;

    case 6: clock = clock / 2048; break;

    case 7: clock = clock / 4096; break;

    default: clock = 0; break;

  }

  neorv32_uart_printf("New I2C clock: %u Hz\n", clock);

}

/**********************************************************************//**

 * Scan 7-bit TWI address space and print results

 **************************************************************************/

void scan_twi(void) {

  neorv32_uart_printf("Scanning TWI bus...\n");

  uint8_t i, num_devices = 0;

  for (i=0; i<128; i++) {

    uint8_t twi_ack = neorv32_twi_start_trans((uint8_t)(2*i+1));

    neorv32_twi_generate_stop();

    if (twi_ack == 0) {

      neorv32_uart_printf("+ Found device at write-address 0x%x\n", (uint32_t)(2*i));

      num_devices++;

    }

  }

  if (!num_devices) {

    neorv32_uart_printf("No devices found.\n");

  }

}

/**********************************************************************//**

 * Read/write menu to transfer 1 byte from/to bus

 **************************************************************************/

void send_twi(void) {

  char terminal_buffer[4];

  // enter data

  neorv32_uart_printf("Enter TX data (2 hex chars): ");

  neorv32_uart_scan(terminal_buffer, 3, 1); // 2 hex chars for address plus '\0'

  uint8_t tmp = (uint8_t)hexstr_to_uint(terminal_buffer, strlen(terminal_buffer));

  uint8_t res = neorv32_twi_trans(tmp);

  neorv32_uart_printf("\nRX data:  0x%x\n", (uint32_t)neorv32_twi_get_data());

  neorv32_uart_printf("Response: ");

  if (res == 0)

    neorv32_uart_printf("ACK\n");

  else

    neorv32_uart_printf("NACK\n");

}

/**********************************************************************//**

 * Helper function to convert N hex chars string into uint32_T

 *

 * @param[in,out] buffer Pointer to array of chars to convert into number.

 * @param[in,out] length Length of the conversion string.

 * @return Converted number.

 **************************************************************************/

uint32_t hexstr_to_uint(char *buffer, uint8_t length) {

  uint32_t res = 0, d = 0;

  char c = 0;

  while (length--) {

    c = *buffer++;

    if ((c >= '0') && (c <= '9'))

      d = (uint32_t)(c - '0');

    else if ((c >= 'a') && (c <= 'f'))

      d = (uint32_t)((c - 'a') + 10);

    else if ((c >= 'A') && (c <= 'F'))

      d = (uint32_t)((c - 'A') + 10);

    else

      d = 0;

    res = res + (d << (length*4));

  }

  return res;

}