main.c

ARM AT91 system introduction, including complete set of source code

/*-----------------------------------------------------------------------------
 * Function Name       : configure_leds
 * Object              : Configure pios to control led states
 *-----------------------------------------------------------------------------*/
static void configure_leds(void)
{
  /* Configure the pin in output */
  AT91C_BASE_PIOA->PIO_OER = (LED_A | LED_B);
  /* Set the PIO controller in PIO mode instead of peripheral mode */
  AT91C_BASE_PIOA->PIO_PER = (LED_A | LED_B);
  /* Disable pull-up */
  AT91C_BASE_PIOA->PIO_PPUDR = (LED_A | LED_B);

  /* Set the default state for the led */
  if (led_a_active)
    AT91C_BASE_PIOA->PIO_SODR = LED_A;
  else
    AT91C_BASE_PIOA->PIO_CODR = LED_A;

  if (led_b_active)
    AT91C_BASE_PIOA->PIO_SODR = LED_B;
  else
    AT91C_BASE_PIOA->PIO_CODR = LED_B;
}


/*-----------------------------------------------------------------------------
 * Function Name       : timer_handler
 * Object              : Handler for TC interrupt
 *-----------------------------------------------------------------------------*/
void timer_handler(void)
{
  volatile unsigned long dummy;
  /* Clear status bit */
  dummy = AT91C_BASE_TC0->TC_SR;

  /* Toggle LED state */
  if (AT91C_BASE_PIOA->PIO_ODSR & LED_B) {
    AT91C_BASE_PIOA->PIO_CODR = LED_B;
  } else {
    AT91C_BASE_PIOA->PIO_SODR = LED_B;
  }
}


/*-----------------------------------------------------------------------------
 * Function Name       : configure_tc
 * Object              : Configure TC
 *-----------------------------------------------------------------------------*/
static void configure_tc(void)
{
    volatile unsigned long dummy;

    /* Enable periph clock for the PIO controller */
    AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC0);

    /* Enable the periph */
    /* Disable the clock and the interrupts */
    AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS;
    AT91C_BASE_TC0->TC_IDR = 0xFFFFFFFF;

    /* Clear status bit */
    dummy = AT91C_BASE_TC0->TC_SR;

    /* Set the Mode of the Timer Counter */
    AT91C_BASE_TC0->TC_CMR = AT91C_TC_CLKS_TIMER_DIV5_CLOCK | AT91C_TC_CPCTRG;
    AT91C_BASE_TC0->TC_RC = AT91B_SLOW_CLOCK >> 2;  /* SLOW_CLOCK divided by 4 */

    /* Enable interrupts */
    /* Disable the interrupt on the interrupt controller */
    AT91C_BASE_AIC->AIC_IDCR = (1 << AT91C_ID_TC0);
    /* Save the interrupt handler routine pointer and the interrupt priority */
    AT91C_BASE_AIC->AIC_SVR[AT91C_ID_TC0] = (unsigned long) timer_handler;
    /* Store the Source Mode Register */
    AT91C_BASE_AIC->AIC_SMR[AT91C_ID_TC0] = AT91C_AIC_SRCTYPE_INT_LEVEL_SENSITIVE | AT91C_AIC_PRIOR_LOWEST;
    /* Clear the interrupt on the interrupt controller */
    AT91C_BASE_AIC->AIC_ICCR = (1 << AT91C_ID_TC0);

    AT91C_BASE_TC0->TC_IER = AT91C_TC_CPCS;

    /* Enable the interrupt on the interrupt controller */
    AT91C_BASE_AIC->AIC_IECR = (1 << AT91C_ID_TC0);

    /* Enable the LED B timer */
    if (led_b_active) {
      /* Clock is started */
      AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN;
      /* Counter is reset and the clock is started */
      AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG;
    }
}


/*----------------------------------------------------------------------------
 * Function Name       : dbgu_print_ascii
 * Object              : This function is used to send a string through the
 *                       DBGU channel (Very low level debugging)
 *----------------------------------------------------------------------------*/
void dbgu_print_ascii (const char *buffer)
{
    while (*buffer != '\0') {
        while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY));
        AT91C_BASE_DBGU->DBGU_THR = (*buffer++ & 0x1FF);
    }
}


/*----------------------------------------------------------------------------
 * Function Name       : dbgu_print_hex8
 * Object              : This function is used to print a 32-bit value in hexa
 *----------------------------------------------------------------------------*/
void dbgu_print_hex8 (unsigned long value)
{
    char c = 0;
    char shift = sizeof(unsigned long) * 8;

    dbgu_print_ascii("0x");
    do {
        shift -= 4;
        while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY));
        c = ((value >> shift) & 0xF);
        if (c > 9)
	  AT91C_BASE_DBGU->DBGU_THR = (('A' + (c - 10)) & 0x1FF);
        else
	  AT91C_BASE_DBGU->DBGU_THR = (('0' + c) & 0x1FF);
    } while (shift != 0);
}


/*-----------------------------------------------------------------------------
 * Function Name       : configure_dbgu
 * Object              : Configure DBGU
 *-----------------------------------------------------------------------------*/
static void configure_dbgu (void)
{
    /* Reset and disable receiver */
    AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RSTRX | AT91C_US_RSTTX;

    /* Disable interrupts */
    AT91C_BASE_DBGU->DBGU_IDR = 0xFFFFFFFF;

    /* Configure PIOs for DBGU */
    AT91C_BASE_PIOA->PIO_ASR = AT91C_PA9_DRXD | AT91C_PA10_DTXD;
    AT91C_BASE_PIOA->PIO_BSR = 0;
    AT91C_BASE_PIOA->PIO_PDR = AT91C_PA9_DRXD | AT91C_PA10_DTXD;

    /* === Configure serial link === */
    /* Define the baud rate divisor register [BRGR = MCK / (115200 * 16)] */
    AT91C_BASE_DBGU->DBGU_BRGR = 54;
    /* Define the USART mode */
    AT91C_BASE_DBGU->DBGU_MR = AT91C_US_PAR_NONE | AT91C_US_CHMODE_NORMAL;

    /* Disable the RX and TX PDC transfer requests */
    AT91C_BASE_DBGU->DBGU_PTCR = AT91C_PDC_RXTDIS;
    AT91C_BASE_DBGU->DBGU_PTCR = AT91C_PDC_TXTDIS;

    /* Enable transmitter */
    AT91C_BASE_DBGU->DBGU_CR = AT91C_US_TXEN;
}

/*-----------------------------------------------------------------------------
 * Function Name       : wait
 * Object              : Tempo using jiffies (updated by PITC)
 *-----------------------------------------------------------------------------*/
void wait (unsigned long ms)
{
  volatile unsigned long current_time = jiffies;
  unsigned long prev_jiffies;
  unsigned long target_time = current_time + ms;

  // Handle the counter overflow
  if (target_time < current_time) {
    prev_jiffies = current_time;
    while (prev_jiffies <= jiffies)
      prev_jiffies = jiffies;
  }
  // Loop until the target time is reached
  while (jiffies < target_time);
}


/*-----------------------------------------------------------------------------
 * Function Name       : Main
 * Object              : Software entry point
 *-----------------------------------------------------------------------------*/
int main()
{
  /* ==== PITC configuration ==== */
  configure_pit();

  /* ==== TIMER configuration ==== */
  configure_tc();

  /* === BUTTON configuration === */
  configure_buttons();

  /* === LED configuration === */
  configure_leds();

  /* ==== DBGU configuration ==== */
  configure_dbgu();

  dbgu_print_ascii("AT91SAM9261 Getting Started program launched ...\n\r");
  dbgu_print_ascii("AT91SAM9261 chip ID : ");
  dbgu_print_hex8(AT91C_BASE_DBGU->DBGU_CIDR);
  dbgu_print_ascii("\n\r");

  while (1) {
    if (led_a_active) {
      /* Switch on the led */
      wait(500);
      AT91C_BASE_PIOA->PIO_CODR = LED_A;

       /* Switch off the led */
      wait(500);
      AT91C_BASE_PIOA->PIO_SODR = LED_A;
    }
  }
}