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// # << NEORV32 - External Interrupt Controller (XIRQ) Demo Program >>                             #

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// # BSD 3-Clause License                                                                          #

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// # Copyright (c) 2021, Stephan Nolting. All rights reserved.                                     #

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

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

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

 * @file demo_xirq/main.c

 * @author Stephan Nolting

 * @brief External interrupt controller (XIRQ) demo program (using hardware-assisted prioritization).

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

#include <neorv32.h>

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

 * @name User configuration

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

/**@{*/

/** UART BAUD rate */

#define BAUD_RATE 19200

/**@}*/

// prototypes

void xirq_handler_ch0(void);

void xirq_handler_ch1(void);

void xirq_handler_ch2(void);

void xirq_handler_ch3(void);

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

 * Main function

 *

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

 *

 * @return 0 if execution was successful

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

int main() {

  // initialize the neorv32 runtime environment

  // this will take care of handling all CPU traps (interrupts and exceptions)

  neorv32_rte_setup();

  // setup UART0 at default baud rate, no parity bits, ho hw flow control

  neorv32_uart0_setup(BAUD_RATE, PARITY_NONE, FLOW_CONTROL_NONE);

  // check if XIRQ unit is implemented at all

  if (neorv32_xirq_available() == 0) {

    neorv32_uart0_printf("XIRQ not synthesized!\n");

    return 1;

  }

  // intro

  neorv32_uart0_printf("External interrupt controller (XIRQ) demo program\n\n");

  int err_cnt = 0;

  // initialize XIRQ controller

  // this will disable all XIRQ channels and will also clear any pending external interrupts

  // (details: this will register the XIRQ's second-level interrupt handler in the NEORV32 RTE)

  err_cnt = neorv32_xirq_setup();

  // check if setup went fine

  if (err_cnt) {

    neorv32_uart0_printf("Error during XIRQ setup!\n");

    return 1;

  }

  // install handler functions for XIRQ channel 0,1,2,3. note that these functions are "normal" functions!

  // (details: these are "third-level" interrupt handlers)

  // neorv32_xirq_install() also enables the specified XIRQ channel and clears any pending interrupts

  err_cnt = 0;

  err_cnt += neorv32_xirq_install(0, xirq_handler_ch0); // handler function for channel 0

  err_cnt += neorv32_xirq_install(1, xirq_handler_ch1); // handler function for channel 1

  err_cnt += neorv32_xirq_install(2, xirq_handler_ch2); // handler function for channel 2

  err_cnt += neorv32_xirq_install(3, xirq_handler_ch3); // handler function for channel 3

  // check if installation went fine

  if (err_cnt) {

    neorv32_uart0_printf("Error during XIRQ install!\n");

    return 1;

  }

  // allow XIRQ to trigger CPU interrupt

  neorv32_xirq_global_enable();

  // enable global interrupts

  neorv32_cpu_eint();

  // the code below assumes the XIRQ inputs are connected to the processor's GPIO output port

  // so we can trigger the IRQs from software; if you have connected the XIRQs to buttons you

  // can remove the code below (note the trigger configuration using the XIRQ generics!)

  {

    // trigger XIRQs 3:0 at once

    // assumes xirq_i(31:0) <= gpio.output(31:0)

    // due to the prioritization this will execute

    // -> xirq_handler_ch0

    // -> xirq_handler_ch1

    // -> xirq_handler_ch2

    // -> xirq_handler_ch3

    neorv32_gpio_port_set(0xF); // set output pins 3:0 -> trigger XIRQ 3:0

    neorv32_gpio_port_set(0x0);

  }

  // --- wait for interrupts ---

  // All incoming XIRQ interrupt requests are "prioritized" in this example. The XIRQ FIRQ handler

  // reads the ID of the interrupt with the highest priority from the XIRQ controller ("source" register) and calls the according

  // handler function (installed via neorv32_xirq_install();).

  // Non-prioritized handling of interrupts (or custom prioritization) can be implemented by manually reading the

  // XIRQ controller's "pending" register. Then it is up to the software to define which pending IRQ should be served first.

  while(1);

  // just as an example: to disable certain XIRQ interrupt channels, we can

  // un-install the according handler. this will also clear a pending interrupt for that channel

  neorv32_xirq_uninstall(0); // disable XIRQ channel 0 and remove associated handler

  neorv32_xirq_uninstall(1); // disable XIRQ channel 1 and remove associated handler

  neorv32_xirq_uninstall(2); // disable XIRQ channel 2 and remove associated handler

  neorv32_xirq_uninstall(3); // disable XIRQ channel 3 and remove associated handler

  // you can also manually clear pending interrupts

  neorv32_xirq_clear_pending(0); // clear pending interrupt of channel 0

  // manually enable and disable XIRQ channels

  neorv32_xirq_channel_enable(0); // enable channel 0

  neorv32_xirq_channel_disable(0); // disable channel 0

  // globally enable/disable XIRQ CPU interrupt

  // this will not affect the XIR configuration / pending interrupts

  neorv32_xirq_global_enable();

  neorv32_xirq_global_disable();

  return 0;

}

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

 * XIRQ handler channel 0.

 *

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

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

void xirq_handler_ch0(void) {

  neorv32_uart0_printf("XIRQ interrupt from channel %i\n", 0);

}

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

 * XIRQ handler channel 1.

 *

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

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

void xirq_handler_ch1(void) {

  neorv32_uart0_printf("XIRQ interrupt from channel %i\n", 1);

}

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

 * XIRQ handler channel 2.

 *

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

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

void xirq_handler_ch2(void) {

  neorv32_uart0_printf("XIRQ interrupt from channel %i\n", 2);

}

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

 * XIRQ handler channel 3.

 *

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

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

void xirq_handler_ch3(void) {

  neorv32_uart0_printf("XIRQ interrupt from channel %i\n", 3);

}