Blinking LED

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Test Environments

Description

Due to technical differences, each board requires a different program to make the LED blink. This document provides individual examples for each of them.
Note that only Ethernut 3 has an on-board User LED. For the other boards you need an extra LED + series resistor.
When using a standard LED the resistor may have a value of 200 Ohm to 1 kOhm. Note, that LEDs do have a polarity and typically one of the two leads is longer than the other one. The longer lead is the anode and will be connected to the resistor.

Ethernut 1.3 / Ethernut 2.1

Description

On these boards, we use pin 2 of PORT E which is reffered to as Pin 41 in the hardware manuals as our digital output pin and pin 3 as +5V Power Supply.
Connect the resistor to pin 3 and the LEDs cathode to pin 41.

Source Code

#include <sys/timer.h>
 
int main(void)
{
sbi(DDRE, 2);
    for(;;){
        cbi(PORTE, 2);
        NutSleep(500);
        sbi(PORTE, 2);
        NutSleep(500);
    }
    return 0;
}

Output

Blinking LED

Details

#include <sys/timer.h>

provides a library, required by NutSleep().

sbi(DDRE, 2);

sets bit 2 of the Data direction register E high, which makes the Pin work as an output.

Within the endless loop,

cbi(PORTE, 2);

drives bit (pin) 2 of Port E low, which makes the LED lit.

NutSleep(500);

After a NutSleep() (delay) of 500ms,

sbi(PORTE, 2);

drives Pin 2 of Port E high again, swiching the LED off.
After another NutSleep() of 500ms the loop continues cycling.

Ethernut 3

Description

Ethernut 3 provides an on-board User LED (green LED integrated in the reset button.)

Source Code

#include <dev/npl.h>
#include <dev/npluled.h>
#include <sys/timer.h>
 
int main(void)
{
    for(;;){
        NplUledCntl(ULED_ON);
        NutSleep(500);
        NplUledCntl(ULED_OFF);
        NutSleep(500);
    }
	    return 0;
}

Output

Blinking LED

Details

#include <dev/npl.h>
#include <dev/npluled.h>
#include <sys/timer.h>

provide prototypes, of functions used later.

Within the endless loop,

NplUledCntl(ULED_ON);

switches the LED ON.

NutSleep(500);

After a NutSleep() (delay) of 500ms,

NplUledCntl(ULED_OFF);

switches the LED OFF again.
After another NutSleep() of 500ms the loop continues cycling.

Elektor Internet Radio 1.0

Description

On the EIR we use pin 1 of port A (pin 2 of header K1) as digital output and pin 34 of header K1 as +3,3V power supply.
Connect the resistor to pin 34 of header K1, the LEDs cathode to pin 2 of header K1.

Source Code

#include <sys/timer.h>
 
int main(void)
{
    outr(PIOA_PER, 2);
    outr(PIOA_OER, 2);
 
    for (;;){
        outr(PIOA_CODR, 2);
        NutSleep(500);
        outr(PIOA_SODR, 2);
        NutSleep(500);
    }
    return 0;
}

Output

Blinking LED

Details

#include <sys/timer.h>

provides a header file, required by NutSleep(). Within the main() function,

outr(PIOA_PER, 2);

enables PIO (Parallel Input Output Controller) at port A bit 1. This disables any peripheral function on this port bit.

outr(PIOA_OER, 2);

configures port A bit 1 as an output.

Within the endless loop,

outr(PIOA_CODR, 2);

drives bit (pin) 1 of port A low, which makes the LED lit.

NutSleep(500);

After a NutSleep() (delay) of 500ms,

outr(PIOA_SODR, 2);

drives Pin 1 of Port A high again, swiching the LED off.

After another NutSleep() of 500ms the loop continues cycling.
(To better understand this commands, have a look at chapter 34 of Atmels documentation on the AT91SAM7SE512.)

See also

• More Nut/OS Examples

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