Step 4.1: Configure Power Manager (PM) Peripheral Library
The Power Manager (PM) is added by default to the project graph. Select the PM peripheral library in the Project Graph window and configure it as shown below.
- Set the Performance Level Select to Performance Level 0 to reduce the power consumption of the device during Standby mode.
- Enable 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 operation in Standby Mode to operate in Low Power oriented mode during standby to reduce the power consumption of the device even more.
This completes the configuration of the PM peripheral library. In Standby mode, the CPU as well as the peripherals (except those which are configured to run in Standby mode) are stopped. 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.
Step 4.2: Configure SUPC Peripheral Library
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.
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.
Step 4.3: Configure 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 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 cannot 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.
This completes the configuration of the NVMCTRL peripheral library. The NVMCTRL is set to optimize the performances for waking the device up while keeping the power consumption as low as possible.
Step 4.4: Configure LED and Wake-up Test Pins
Once the Plugins Pin Settings window is opened, scroll-down to pin number PA06 and PA07, and then configure these pins as shown below:
- Set the Pin Number #7 as GPIO:
- Pin ID = PA06
- Custom Name = TEST_GPIO
- Function = GPIO
- Direction = Out
- Latch = Low
- Set the Pin Number #8 as GPIO:
- Pin ID = PA07
- Custom Name = LED0
- Function = GPIO
- Direction = Out
- Latch = High
Step 4.5: Rename the default main file
Under the Project Graph tab, click on System, and configure as below to give a name of your liking to the default template main file generated by the MCC.
The name of the default main.c is changed to main_l10.c to indicate that the referred main.c is for the Low Power application on SAM L10.