Subversion Repositories neorv32

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

// # << NEORV32 - RISC-V Machine Timer (MTIME) Demo Program >>                                     #

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

// # BSD 3-Clause License                                                                          #

// #                                                                                               #

// # Copyright (c) 2022, Stephan Nolting. All rights reserved.                                     #

// #                                                                                               #

// # Redistribution and use in source and binary forms, with or without modification, are          #

// # 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. Redistributions in binary form must reproduce the above copyright notice, this list of     #

// #    conditions and the following disclaimer in the documentation and/or other materials        #

// #    provided with the distribution.                                                            #

// #                                                                                               #

// # 3. Neither the name of the copyright holder nor the names of its contributors may be used to  #

// #    endorse or promote products derived from this software without specific prior written      #

// #    permission.                                                                                #

// #                                                                                               #

// # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS   #

// # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF               #

// # MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE    #

// # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,     #

// # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE #

// # GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED    #

// # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING     #

// # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED  #

// # OF THE POSSIBILITY OF SUCH DAMAGE.                                                            #

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

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

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

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

 * @file demo_mtime/main.c

 * @author Stephan Nolting

 * @brief Simple machine timer (MTIME) usage example.

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

#include <neorv32.h>

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

 * @name User configuration

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

/**@{*/

/** UART BAUD rate */

#define BAUD_RATE 19200

/**@}*/

// Prototypes

void mtime_irq_handler(void);

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

 * This program blinks an LED at GPIO.output(0) at 1Hz using the machine timer interrupt.

 *

 * @note This program requires the MTIME unit to be synthesized (and UART0 and GPIO).

 *

 * @return Should not return;

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

int main() {

  // capture all exceptions and give debug info via UART

  neorv32_rte_setup();

  // init UART at default baud rate, no parity bits, no hw flow control

  neorv32_uart0_setup(BAUD_RATE, PARITY_NONE, FLOW_CONTROL_NONE);

  // check if MTIME unit is implemented at all

  if (neorv32_mtime_available() == 0) {

    neorv32_uart0_print("ERROR! MTIME timer not implemented!\n");

    return 1;

  }

  // Intro

  neorv32_uart0_print("RISC-V Machine System Timer (MTIME) demo Program.\n"

                      "Toggles GPIO.output(0) at 1Hz using the RISC-V 'MTI' interrupt.\n\n");

  // clear GPIO output port

  neorv32_gpio_port_set(0);

  // install MTIME interrupt handler to RTE

  neorv32_rte_exception_install(RTE_TRAP_MTI, mtime_irq_handler);

  // configure MTIME timer's first interrupt to appear after SYSTEM_CLOCK / 2 cycles (toggle at 2Hz)

  // starting from _now_

  neorv32_mtime_set_timecmp(neorv32_mtime_get_time() + (NEORV32_SYSINFO.CLK / 2));

  // enable interrupt

  neorv32_cpu_irq_enable(CSR_MIE_MTIE); // enable MTIME interrupt

  neorv32_cpu_eint(); // enable global interrupt flag

  // go to sleep mode and wait for interrupt

  while(1) {

    neorv32_cpu_sleep();

  }

  return 0;

}

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

 * MTIME IRQ handler.

 *

 * @warning This function has to be of type "void xyz(void)" and must not use any interrupt attributes!

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

void mtime_irq_handler(void) {

  // update MTIMECMP value for next IRQ (in SYSTEM_CLOCK / 2 cycles)

  // this will also ack/clear the current MTIME interrupt request

  neorv32_mtime_set_timecmp(neorv32_mtime_get_timecmp() + (NEORV32_SYSINFO.CLK / 2));

  neorv32_uart0_putc('.'); // send tick symbol via UART

  neorv32_gpio_pin_toggle(0); // toggle output port bit 0

}