MPLAB® Harmony v3 Peripheral Libraries on SAMC2x: Step 2

Last modified by Microchip on 2023/11/09 09:09

Configure I2C, USART, and RTC Peripheral Libraries

Configure RTC Peripheral Library

Click on the Resource Management [MCC] tab, In the Device Resources, expand Peripherals > RTC.
Double-click or drag and drop RTC to add the RTC peripheral library (PLIB) to the project graph.

RTC Adding​​

Verify that the RTC clock is set to run at 1 kHz internal ultra-low power clock.

When a module is added to the project graph, MPLAB® Code Configurator (MCC) automatically enables the clock to the module. The default RTC clock source is internal 1 kHz ultra-low power clock (OSCULP1K).
RTC Clock Setup​​

Note: On the SAMC21N device, RTC can be clocked through several low power clock sources of 1 kHz and 32 kHz as shown above. The 1 kHz clock source retained (OSCULP1K) is enough to generate time periods of 500 milliseconds, 1 second, 2 seconds, and 4 seconds.

Go back to the project graph and configure the RTC PLIB to generate a compare interrupt every 500 milliseconds.
RTC configuration setup

Note: The Compare Value is set as 0x200. This compare value generates an RTC compare interrupt every 500 milliseconds

  • RTC clock = 1024 Hz
  • RTC Prescaler = 1
  • Required Interrupt rate = 500 ms

Hence, Compare Value = (500/1000) x 1024 = 512 (0x200).

Back to Top

Configure I²C Peripheral Library and I²C pins

Under the left tab Resource Management (MCC), go to Device Resources and expand Libraries > Harmony > Peripherals > SERCOM.

Double-click on SERCOM5 to add the SERCOM instance 5 to the project.

SERCOM Selection

Select the SERCOM5 peripheral library and configure it for I²C protocol as shown.

Note: The SERCOM5 (as I²C) retains the default 100 kHz speed because the temperature sensor chip on I/O1 Xplained Pro Extension Kit can operate at 100 kHz I²C speed.

 Open the Pin Configuration tabs by clicking Project Graph > Plugins > Pin Configuration.

Open pin configuration

Select the Project Graph > Plugins > Pin Settings tab and sort the entries by Port names as shown: 

SERCOM pin setup

Now, select the Plugins > Pin Table tab and then scroll down to the SERCOM5 module as shown:

  • Enable I²C Clock (TWI_SCL) on PB17 (Pin #65)
  • Enable I²C Data (TWI_SDA) on PB16 (Pin #64)

SERCOM pin setup

Note: This completes the configuration of the I²C peripheral library. The application code will use the I²C PLIB APIs to read temperature from the temperature sensor.

Back to Top

Configure USART Peripheral Library and USART pins

Under the left tab Resource Management (MCC), go to Device Resources and expand Libraries > Harmony > Peripherals > SERCOM.

Double-click on SERCOM4 to add the SERCOM instance 4 to the project.

SERCOM Selection for UART

Select the SERCOM4 peripheral library in the Project Graph and configure it for Universal Synchronous Asynchronous Receiver Transmitter (USART) protocol as shown:


Verify the default baud rate is set to 115200 Hz.

Note: The application will use the SERCOM4 (as USART) PLIB for printing messages on the serial terminal. Hence, only the transmit functionality is enabled and the receive functionality is disabled.

Select the Pin Table tab and then scroll down to the SERCOM4 module as shown:

Enable USART_TX on PB10 (Pin #30).


Note: In the SERCOM4 (as USART) configuration, USART is enabled for TX functionality and no USART Rx functionality is enabled.

Back to Top

Configure DMA Peripheral Library

From the Project Graph tab, select Plugins > DMA Configuration to launch the DMA Configuration window.

Open DMA Configuration

Click on the DMA Settings tab. Configure DMA Channel 0 to transfer application buffer to the USART TX register. The DMA transfers one byte from user buffer to USART transmit buffer on each trigger.

Based on the trigger source, the DMA channel configuration is automatically set by MCC.

  • Trigger Action: Action taken by DMA on receiving a trigger.
    • One beat transfer: Generally used during a memory-to-peripheral or peripheral-to-memory transfer.
    • One block transfer: Generally used during the memory-to-memory transfer on a software trigger.
  • Source Address Mode, Destination Address Mode: Select whether to increment Source/Destination Address after every transfer. Automatically set by MCC based on the trigger type. For example:
    • If the trigger source is USART transmit, then the Source Address is incremented and the Destination Address is fixed.
    • If the trigger source is USART receive, then the Source Address is fixed and the Destination Address is incremented.
  • Beat Size: Size of one beat. The default value is 8-bits. For example:
    • If the Serial Peripheral Interface (SPI) peripheral is configured for 16-bit/32-bit mode, then the beat size must be set to 16-bits/32-bits respectively.
  • Enable Interrupts: In this Tab, SERCOM4 (as USART) Interrupt is enabled.


Back to Top