4 Adding Application Logic to the Project

To develop and run the application, follow these steps:

Add the required macro and variables outside the main() function in the main.c file.

#define ADC_VREF                (5.0f)

uint16_t adc_count[3];
volatile bool transferDone = false;
float inp_voltage[3];

Add a DMAC callback function outside the main() function in the main.c file.

void DMAC_Callback(DMAC_TRANSFER_EVENT status, uintptr_t context)
{
    if(status == DMAC_TRANSFER_EVENT_COMPLETE)
    {
        // Transfer is completed.
        transferDone = true;
    }
}

Figure 4-1. Adding Macro and DMAC Callback Function and Variables

Add the printf statements, DMAC callback register function, DMAC channel transfer function, ADC enable function, and the Timer Start function inside the main() function as shown below:

printf("\n\r---------------------------------------------------------");
printf("\n\r                 ADC Sequencer Demo                    ");
printf("\n\r---------------------------------------------------------\n\r");
    
TC0_TimerStart();
    
ADC0_Enable();

DMAC_ChannelCallbackRegister(DMAC_CHANNEL_0, DMAC_Callback, 0);
DMAC_ChannelTransfer(DMAC_CHANNEL_0, (const void *)&ADC0_REGS->ADC_RESULT, &adc_count, sizeof(adc_count));

Inside the while loop, add the application logic as shown below:

if(transferDone == true)
        {
            transferDone = false;
            for(int i = 0; i<3;i++)
            {
                /* The below formula is used to find the voltage for the 
                   corresponding ADC value.
                   Input_Volt = (ADC_count * Ref_Volt)/(2^No.of Bits); 
                   Where Ref_Volt = 5V and No. of Bits = 12*/
               inp_voltage[i] = (float)adc_count[i] * ADC_VREF / 4095U; 
            }           
            printf("\rADC0 Count = 0x%x, ADC0 Voltage = %d.%02d V, "
                    "ADC1 Count = 0x%x, ADC1 Voltage = %d.%02d V, "
                    "ADC2 Count = 0x%x, ADC2 Voltage = %d.%02d V ", 
                    adc_count[0], (int)inp_voltage[0], (int)((inp_voltage[0] -         (int)inp_voltage[0])*100.0),
                    adc_count[1], (int)inp_voltage[1], (int)((inp_voltage[1] - (int)inp_voltage[1])*100.0),
                    adc_count[2], (int)inp_voltage[2], (int)((inp_voltage[2] - (int)inp_voltage[2])*100.0));
            DMAC_ChannelTransfer(DMAC_CHANNEL_0, (const void *)&ADC0_REGS->ADC_RESULT, 
              &adc_count, sizeof(adc_count));
        }

Note: The formula used in printf statements is to print the integer and the decimal values. In the expression %d.%02d, %d represents the integer value and .%02d represents the decimal value rounded to two places.

Figure 4-2. Adding Application Logic to main.c

Note: The example code shown above is in the main routine inside while (1). This example code can be run in Standby mode or other sub-routine, where the CPU intervention and CPU load reduction can be observed.