Harmony v3 Peripheral Libraries on SAMC2x: Step 5

Step 5: Add application code to the project

The application is already developed and is available in the main_c21n.c file under <your unzip folder>/getting_started /dev_files/sam_c21n_xpro. The main_c21n.c file contains the application logic. It also contains placeholders that you will populate with necessary code in the next step.

  • Go to the getting_started /dev_files/sam_c21n_xpro folder and copy the pre-developed main_c21n.c file.
  • Replace (over-write) the main_c21n.c file of your project available at <Your unzip folder>/getting_started /firmware/src with the copied file.
  • Open main_c21n.c in MPLAB® X IDE and add application code by following the steps below:

1

Under the main_c21n.c file, in function main, notice the call to function SYS_Initialize. The generated function SYS_Initialize initializes all the peripheral modules used in the application (configured through MHC).

Tip: Press the CTRL key and left click on the SYS_Initialize function. The click will open the implementation for the SYS_Initialize function as shown below.

app_code1.png

2

In the main_c21n.c function, below SYS_Initialize(), add the following code to register callback event handlers.

SERCOM5_I2C_CallbackRegister(i2cEventHandler, 0);
DMAC_ChannelCallbackRegister(DMAC_CHANNEL_0, usartDmaChannelHandler, 0);
RTC_Timer32CallbackRegister(rtcEventHandler, 0);
EIC_CallbackRegister(EIC_PIN_3,EIC_User_Handler, 0);

Following the addition of the code above, add the function call.

RTC_Timer32Start();
app_code2.png

Note:

a

The function call SERCOM5_I2C_CallbackRegister registers a callback event handler with the I²C PLIB. The event handler is called by the I²C PLIB when the I²C transfer is complete.

b

The function call DMAC_ChannelCallbackRegister registers a callback event handler with the DMA PLIB. The callback event handler is called by the DMA PLIB when the DMA transfer (of temperature sensor data to serial terminal) is complete.

c

The function call RTC_Timer32CallbackRegister registers an RTC callback event handler with the RTC PLIB. The callback event handler is called by the RTC PLIB when the configured time period has elapsed.

d

The function call EIC_CallbackRegister registers an EIC callback event handler with the EIC PLIB. The callback event handler is called by EIC PLIB when the user presses the switch SW0.

3

Implement the registered callback event handlers for RTC, I²C, USART and EIC PLIBs by adding the following code before
main() function in main_c21n.c.

static void EIC_User_Handler(uintptr_t context)
{
    changeTempSamplingRate = true;      
}

static void rtcEventHandler (RTC_TIMER32_INT_MASK intCause, uintptr_t context)
{
    if (intCause & RTC_MODE0_INTENSET_CMP0_Msk)
    {            
        isRTCTimerExpired = true;                              
    }
}

static void i2cEventHandler(uintptr_t contextHandle)
{
    if (SERCOM5_I2C_ErrorGet() == SERCOM_I2C_ERROR_NONE)
    {
        isTemperatureRead = true;
    }
}

static void usartDmaChannelHandler(DMAC_TRANSFER_EVENT event, uintptr_t contextHandle)
{
    if (event == DMAC_TRANSFER_EVENT_COMPLETE)
    {
        isUSARTTxComplete = true;
    }
}
app_code3.png

4

Add the code below to submit an I²C transfer to read temperature sensor value when the configured time period (default 500 milliseconds) has elapsed. The I²C PLIB calls back the callback event handler (registered in Step 2 above) when the submitted request is complete.

isRTCTimerExpired = false;
SERCOM5_I2C_WriteRead(TEMP_SENSOR_SLAVE_ADDR, &i2cWrData, 1, i2cRdData, 2);
app_code4.png

5

Add the code below to prepare the received temperature value from sensor to be prepared on the serial terminal.

temperatureVal = getTemperature(i2cRdData);
sprintf((char*)uartTxBuffer, "Temperature = %02d F\r\n", temperatureVal);
LED_Toggle();
app_code5.png

6

Add the code below to implement the change of sampling rate and prepare a message for the same on the serial terminal when the user presses the switch SW0.

changeTempSamplingRate = false;
if(tempSampleRate == TEMP_SAMPLING_RATE_500MS)
{
    tempSampleRate = TEMP_SAMPLING_RATE_1S;
    sprintf((char*)uartTxBuffer, "Sampling Temperature every 1 second \r\n");
    RTC_Timer32CompareSet(PERIOD_1S);
}
else if(tempSampleRate == TEMP_SAMPLING_RATE_1S)
{
    tempSampleRate = TEMP_SAMPLING_RATE_2S;
    sprintf((char*)uartTxBuffer, "Sampling Temperature every 2 seconds \r\n");        
    RTC_Timer32CompareSet(PERIOD_2S);                        
}
else if(tempSampleRate == TEMP_SAMPLING_RATE_2S)
{
    tempSampleRate = TEMP_SAMPLING_RATE_4S;
    sprintf((char*)uartTxBuffer, "Sampling Temperature every 4 seconds \r\n");        
    RTC_Timer32CompareSet(PERIOD_4S);                                        
}    
else if(tempSampleRate == TEMP_SAMPLING_RATE_4S)
{
   tempSampleRate = TEMP_SAMPLING_RATE_500MS;
   sprintf((char*)uartTxBuffer, "Sampling Temperature every 500 ms \r\n");        
   RTC_Timer32CompareSet(PERIOD_500MS);
}
else
{
    ;
}
app_code6.png

7

Add code to transfer the buffer containing either:

  • the latest temperature value in the format “Temperature = XX F\r\n”, over or
  • the message mentioning the change of sampling rate over USART using DMA.
DMAC_ChannelTransfer(DMAC_CHANNEL_0, uartTxBuffer, (const void *)&(SERCOM4_REGS->USART_INT.SERCOM_DATA), strlen((const char*)uartTxBuffer));
app_code7.png

You are now ready to build the code!


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