Starting with Simple Current Measurements

Lets start by writing an application to flash the LED on the Xplained Mini board. We will use a delay loop with a NOP instruction inside a large counter and pulse the LED with about a 1% duty cycle. The code for low_power_101 is shown here.

#include <avr/io.h>

void delay (uint16_t length)
{
    // Simple delay loop
    for (uint16_t i=0; i<length; i++) {
        for (uint8_t j=0; j<255; j++) {
            asm volatile("nop");
        }
    }
}

int main(void)
{
    // PORTB5 to output
    DDRB = (1 << 5);
    // Do forever:
    while (1) {
        // PORTB5 on
        PORTB = (1 << 5);
        // Short delay
        delay(50);
        // PORB5 off
        PORTB = 0x00;
        // Long delay
        delay(5000);
    }
}

Important: For this example set the optimisation level to None (-O0) in the project options under Toolchain → AVR/GNU C Compiler → Optimization.

Todo: Build the project/solution (F7).

Todo: Program the application into the target by selecting Start Without Debugging (Ctrl+Alt+F5).

Info: In this example we are going to make use of programming mode only. In most systems running code through a debugger will not yield accurate current measurements. This is because the target device's debug module (OCD) requires a clock source which cannot be disabled while debugging.

Important: Remember to disable on-board power on the Xplained Mini.