Radix cross Linux

#include <stdint.h>
#include <string.h>

// Device header files.
#include <gd32vf103.h>
#include <riscv_encoding.h>

/*
  Uncomment this line if you have only -march=rv32imac instead of -march=rv32imac_zicsr:
__asm("\t.option arch, +zicsr");
 */

/* Pre-defined memory locations for program initialization */
extern uint32_t _sidata, _sdata, _edata, _sbss, _ebss;
/* Current system core clock speed */
volatile uint32_t SystemCoreClock = 8000000;

/* Simple 'busy loop' delay method */
__attribute__( ( optimize( "O0" ) ) )
void delay_cycles( uint32_t cyc ) {
  uint32_t d_i;
  for ( d_i = 0; d_i < cyc; ++d_i ) { __asm__( "nop" );
  }
}

/* 'main' method which gets called from the boot code */
int main( void )
{
  /* Copy initialized data from .sidata (Flash) to .data (RAM) */
  memcpy( &_sdata, &_sidata, ( ( void* )&_edata - ( void* )&_sdata ) );
  /* Clear the .bss RAM section */
  memset( &_sbss, 0x00, ( ( void* )&_ebss - ( void* )&_sbss ) );

  /* Enable the GPIOA and GPIOC peripherals */
  RCC->APB2ENR |=  ( RCC_APB2ENR_IOPAEN |
                     RCC_APB2ENR_IOPCEN );

  /* Configure pins A1, A2, and C13 as low-speed push-pull outputs */
  GPIOA->CRL   &= ~( GPIO_CRL_MODE1 | GPIO_CRL_CNF1 |
                     GPIO_CRL_MODE2 | GPIO_CRL_CNF2 );
  GPIOA->CRL   |=  ( ( 0x2 << GPIO_CRL_MODE1_Pos ) |
                     ( 0x2 << GPIO_CRL_MODE2_Pos ) );
  GPIOC->CRH   &= ~( GPIO_CRH_MODE13 | GPIO_CRH_CNF13 );
  GPIOC->CRH   |=  ( 0x2 << GPIO_CRH_MODE13_Pos );

  /********************************************************
    Turn all three LEDs off.
    The pins are connected to the LED cathodes, so pulling
    the pin high turns the LED off, and low turns it on.
   */
  GPIOA->ODR   |=  ( 0x1 << 1 |
                     0x1 << 2 );
  GPIOC->ODR   |=  ( 0x1 << 13 );

  /* Cycle the RGB LED through a pattern of colors */
  #define DELAY_CYCLES ( 50000 )
  while( 1 )
  {
    /* Green on (Green) */
    GPIOA->ODR &= ~( 0x1 << 1 );
    delay_cycles( DELAY_CYCLES );
    /* Red on (Yellow) */
    GPIOC->ODR &= ~( 0x1 << 13 );
    delay_cycles( DELAY_CYCLES );
    /* Blue on (White) */
    GPIOA->ODR &= ~( 0x1 << 2 );
    delay_cycles( DELAY_CYCLES );
    /* Green off (Purple) */
    GPIOA->ODR |=  ( 0x1 << 1 );
    delay_cycles( DELAY_CYCLES );
    /* Red off (Blue) */
    GPIOC->ODR |=  ( 0x1 << 13 );
    delay_cycles( DELAY_CYCLES );
    /* Blue off (Off) */
    GPIOA->ODR |=  ( 0x1 << 2 );
    delay_cycles( DELAY_CYCLES );
  }
  return 0;
}