Getting Started with USB on SAM MCUs Using MPLAB® Harmony v3: Step 3

Step 3.1 - Configure Clocks

1

Open Clock Configuration pane by navigating to MHC > Tools > Clock Configuration.

tools_clock_config.png
Figure 1: Open Clock Configuration

2

Switch MOSCSEL to Main Crystal.

Note: USB requires an accurate clock for operation and cannot run on the Main RC oscillator.

clock_config_window_1.png
Figure 2: Clock Configuration

Step 3.2 - Configure Pins

1

Open the Pin Configuration pane by navigating to MHC > Tools > Pin Configuration.

tools_pin_config.png
Figure 3: Open Pin Configuration

2

Order the pins by Ports for ease of use.

pin_config_window_1_1.png
Figure 4: Order by Ports

3

The LED on the I/O1 Xplained Pro is connected to pin PA0.

  • Set the function to GPIO.
  • Name this pin as "LED".
  • Set the direction to Out.
  • Set the latch to High.

TWIHS pins, PA3 and PA4, need to be set to the correct function.

  • For PA3, set function to TWIHS0_TWD0.
  • For PA4, set function to TWIHS0_TWCK0.
pin_config_window_2_1.png
Figure 5: LED and TWIHS Pin Config

4

The LED on the SAM E70 Xplained is connected to pin PC8.

user_leds.png
Figure 6: SAM E70 Xplained User LED Schematic
  • Set the function to GPIO.
  • Name this pin as "USB_LED".
  • Set the direction to Out.
  • Set the latch to High.
pin_config_window_3_1.png
Figure 7: User LED Config

Note: The LEDs on the SAM E70 Xplained and the I/O1 Xplained Pro are active low, so, they are turned off by default by configuring the latch value to logic High.

Step 3.3 - Add and Configure Application Tasks

1

Go to the Project Graph and click on the Core module.

2

Under Configuration Options, you will find that MHC automatically generates a default application named app. Set the Number of Applications spinbox to 3 and configure each of them as follows:

  • Expand Application 0 Configuration and rename the default application name to "app_sensor".
  • Expand Application 1 Configuration and rename the default application name to "app_eeprom".
  • Expand Application 2 Configuration and rename the default application name to "app_usb".
app_tasks_config.png
Figure 8: Configure Application Tasks



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