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

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

Configure PM, SUPC, and NVMCTRL Peripheral Libraries, LED, and Wake-up Test Pins

Configure the Power Manager (PM) Peripheral Library

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

Add Power Manager to the project graph

Select the PM peripheral library and configure it as shown.

  • 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.

PM configuration options

This completes the configuration of the PM peripheral library. In Standby mode, the CPU is stopped as well as the peripherals except those which are configured to run in Standby mode. The Standby Sleep mode provides very low power consumption with little overhead on wake-up time. CPU enters Standby mode by executing the Wait for Interrupt (WFI) instruction and exits from the Standby mode when an interrupt is generated.

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Configure the Supply Controller (SUPC) Peripheral Library

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

Add the Supply Controller 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.

​SUPC configuration options

This completes the configuration of the SUPC peripheral library. The SUPC manages the voltage reference and power supply of the device. It also controls the voltage regulators for the core domain. Voltage regulators need to be configured for low-power applications, which helps in reducing power consumption.

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Configure the Non-volatile Memory Controller (NVMCTRL) Peripheral Library

The Non-volatile Memory Controller (NVMCTRL) is added by default to the project graph. Select the NVMCTRL peripheral library and configure it as shown.

  • 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 the 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.

​NVMCTRL configuration options

This completes the configuration of the NVMCTRL peripheral library. The NVMCTRL is set to optimize the performance for waking the device up while keeping the power consumption as low as possible.

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Configure LED and Wake-up Test Pins

Click Project Graph > Plugins > Pin Configuration to open the Pin Configuration tabs.

Pins settings tool

Once the MPLAB® Code Configurator (MCC) Pin Settings window is opened, scroll down to pin numbers 6 and 23, and then configure these pins as shown.

  • Set the pin #6 as GPIO:
    • Pin ID = PB05
    • Custom Name = TEST_GPIO
    • Function = GPIO
    • Direction = Out
    • Latch = Low
  • Set the pin #23 as GPIO:
    • Pin ID = PB10
    • Custom Name = LED0
    • Function = GPIO
    • Direction = Out
    • Latch = High

Test GPIO pin settings

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