4.3 Add RTC, ADC, and SLPCTRL Functionality in Application Code

Once the RTC, CPUINIT, and SLPCTRL modules have been added and reconfigured using Atmel | START, the application code needs to be updated in Atmel Studio.

1. Update the main.c file:
   1. Include the sleep header file at the top of the file:

      
          #include <avr/sleep.h>
      

   2. Enable the Sleep Standby mode by adding the following piece of code in the main function after initialization:

      
          //Set sleep mode to STANDBY mode
          set_sleep_mode(SLEEP_MODE_STANDBY);
          sleep_enable();
      

   3. Set the device to Sleep mode by replacing the following piece of code in the while-loop of the main function:

        
          //Enter into sleep mode
          sleep_cpu();
      

      The complete code of the main.c file should look like:

      

2. Edit the driver_isrc.c file by double-clicking and open it in the Solution Explorer in Atmel Studio:
   1. Start ADC conversion when RTC interrupt is triggered by adding the following line of code in the RTC interrupt routine:

        
          /* RTC Overflow Interrupt handling */
          ADC_0_start_conversion(10); //start ADC conversion on channel 10
      

   2. Manually add the ADC result ready interrupt routine as:

      
      ISR(ADC0_RESRDY_vect)
      {
          /* ADC result ready Interrupt handling: start USART transmission */
          USART_0_write(ADC_0_get_conversion_result()); //USART write ADC result
          while(!(USART0.STATUS & USART_TXCIF_bm)); //wait for USART TX complete
          USART0.STATUS = USART_TXCIF_bm; //Clear TXCIF flag
      	
          /* The interrupt flag has to be cleared manually */
          ADC0.INTFLAGS = ADC_RESRDY_bm;
      }
      

      In the ADC result ready interrupt routine, the ADC result ready interrupt will trigger for the ADC result to be sent over USART.

      The complete code of driver_isr.c looks like: