Low Power Application on SAM L21 Using MPLAB® Harmony v3 Peripheral Libraries: Step 4

1. Under the bottom left tab, Available Components, expand Peripherals > PM.

Double-click or drag and drop PM to add the PM peripheral library to the project graph.

Select the PM peripheral library and configure it as shown below.

• Set the Performance Level to 0 to reduce the power consumption of the device during Standby mode.
• Enable PD0 and PD1 Dynamic Power Gating: these options allow the device to turn off a power domain during Standby mode if no peripheral contained in this power domain requests its clock.
• Set the Voltage Regulator to operate in Low-power oriented mode during standby to reduce the power consumption of the device even more.

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Under the bottom left tab, Available Components, expand Peripherals > SUPC.

Double-click or drag and drop SUPC to add the Supply Controller (SUPC) peripheral library to the project graph.

Select the SUPC peripheral library and configure it as shown below.

• Enable the Increase low power mode efficiency bit to optimize and reduce power consumption in Standby mode.

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The Non-volatile Memory Controller (NVMCTRL) is added by default to the project graph.

Select the NVMCTRL peripheral library and configure it as shown below.

• Set Wait States to 1 to read the non-volatile memory. When the device is put in performance level 0, the device clock frequency can not exceed 12 MHz and one wait-state is required.
• Set the Power Reduction Mode During Sleep to WAKEUP INSTANT. This bit configures the NVMCTRL to wake-up the Flash memory when the CPU wakes up from Standby mode, which allows it to reduce device wake-up time.
• Disable the Instruction Cache to reduce the device's wake-up time. When the cache is enabled, the device will look for an instruction to fetch upon interrupt in the cache at first. If the instruction is found, the device wakes up quicker, but if not, a cache miss occurs and wake-up time is longer. This option is good to enable when the instruction to fetch upon an interrupt is always stored in the cache memory, which is not the case here as we have different interrupt sources.

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Open the Pin Configuration tabs by clicking Tools > Pin Configuration.

Once the MPLAB^® Harmony Configurator (MHC) Pin Settings window is opened, scroll-down to pin number 6 and 23, and then configure these pins as shown below:

• Set the pin #6 as GPIO:

  • Pin ID = PB05
  • Custom Number = TEST_GPIO
  • Function = GPIO
  • Direction = Out
  • Latch = Low
• Set the pin #23 as GPIO:
  • Pin ID = PB10
  • Custom Number = LED0
  • Function = GPIO
  • Direction = Out
  • Latch = High