neorv32_char_loopback.c

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// #################################################################################################
// # << NEORV32 - Blinking LED Demo Program >> # #
// *********************************************************************************************
// # # BSD 3-Clause License # # # # Copyright (c) 2021, Stephan Nolting. All
// rights reserved.                                     # # # # Redistribution
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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        # #    conditions and the following disclaimer. # # # # 2.
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// # # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan
// Nolting #
// #################################################################################################
 
/**********************************************************************/ /**
                                                                          * @file
                                                                          *blink_led/main.c
                                                                          * @author
                                                                          *Stephan
                                                                          *Nolting
                                                                          * @brief
                                                                          *Simple
                                                                          *blinking
                                                                          *LED
                                                                          *demo
                                                                          *program
                                                                          *using
                                                                          *the
                                                                          *lowest
                                                                          *8
                                                                          *bits
                                                                          *of
                                                                          *the
                                                                          *GPIO.output
                                                                          *port.
                                                                          **************************************************************************/
 
#include <neorv32.h>
#include <stdbool.h>
 
/**********************************************************************/ /**
                                                                          * @name
                                                                          *User
                                                                          *configuration
                                                                          **************************************************************************/
/**@{*/
/** UART BAUD rate */
#define BAUD_RATE 19200
/**@}*/
 
#define UART1_TX_BUFFER_FULL                                                   \
  ((NEORV32_UART1.CTRL & (1 << UART_CTRL_TX_FULL)) != 0)
 
char tmpChar;
char loopbackChar;
bool charReceived = false;
int rx_status;
 
/**********************************************************************/ /**
                                                                          * Main
                                                                          *function;
                                                                          *shows
                                                                          *an
                                                                          *incrementing
                                                                          *8-bit
                                                                          *counter
                                                                          *on
                                                                          *GPIO.output(7:0).
                                                                          *
                                                                          * @note
                                                                          *This
                                                                          *program
                                                                          *requires
                                                                          *the
                                                                          *GPIO
                                                                          *controller
                                                                          *to be
                                                                          *synthesized
                                                                          *(the
                                                                          *UART
                                                                          *is
                                                                          *optional).
                                                                          *
                                                                          * @return
                                                                          *0 if
                                                                          *execution
                                                                          *was
                                                                          *successful
                                                                          **************************************************************************/
int main() {
 
  // init UART (primary UART = UART0; if no id number is specified the primary
  // UART is used) at default baud rate, no parity bits, ho hw flow control
  neorv32_uart0_setup(BAUD_RATE, PARITY_NONE, FLOW_CONTROL_NONE);
 
  if (neorv32_uart1_available() == 0) {
    neorv32_uart0_print("Error! UART1 not synthesized!\n");
    return 1;
  }
 
  // capture all exceptions and give debug info via UART
  // this is not required, but keeps us safe
  neorv32_rte_setup();
 
  neorv32_uart1_setup(9600, PARITY_NONE, FLOW_CONTROL_NONE);
 
  // say hello
  neorv32_uart0_print("Starting UART1 loopback demo program\n");
 
  // Assumes uart has a larger than default fifo
  while (1) {
    if (!charReceived) {
      rx_status = neorv32_uart1_getc_safe(&tmpChar);
      if (rx_status == 0) { // successfully rx a char
        loopbackChar = tmpChar;
        charReceived = true;
      }
    }
    if (charReceived && !UART1_TX_BUFFER_FULL) {
      neorv32_uart1_putc(loopbackChar);
      charReceived = false;
    }
  }
 
  return 0;
}