Subversion Repositories neorv32

// #################################################################################################
// # << NEORV32 - TWI Bus Explorer Demo Program >>                                                 #
// # ********************************************************************************************* #
// # BSD 3-Clause License                                                                          #
// #                                                                                               #
// # Copyright (c) 2020, Stephan Nolting. All rights reserved.                                     #
// #                                                                                               #
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// # permitted provided that the following conditions are met:                                     #
// #                                                                                               #
// # 1. Redistributions of source code must retain the above copyright notice, this list of        #
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// #    provided with the distribution.                                                            #
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// #    endorse or promote products derived from this software without specific prior written      #
// #    permission.                                                                                #
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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;
}