Low Power Application on SAM D21 Using Harmony v3 Peripheral Libraries: Step 7

Step 7.1: Build and Program the Application

1

Clean and build your application by clicking on the Clean and Build clean_build_icon.png button.

In case of compilation errors, recheck the steps and build the project again.

2

Program your application to the device by clicking on the Make and Program program_icon.png button.

3

Open the Tera Term application (or another terminal console) on your PC and navigate to File > New connection.

tera_term_new_connection.png
Figure 1

4

Navigate to the Serial box in the opened window and select the port number that corresponds to the Embedded Debugger (EDGB) Virtual COM Port of your connected SAM D21 Xplained Pro Evaluation Kit. Press OK to open a serial connection.

tera_term_new_connection_window.png
Figure 2

5

Open the Serial port configuration of Tera Term by navigating to Setup > Serial port.

tera_term_serial_port.png
Figure 3

6

In the Serial Port window, verify that the Baud rate is set to 4800 and other elements are set as shown in Figure 4, then press OK.

tera_term_serial_port_setup.png
Figure 4

7

Now that the serial console is configured, reset the board, and verify the application displayed the Measurement Menu along with the application title message.

console_message_after_reset.png
Figure 5

Note: Make sure to keep the complete hardware setup or the light sensor on the I/O1 Xplained Pro board under proper lighting when testing the application, this will help to wake up the device when you cover the light sensor.

8

Select the Power Measurement Mode by entering option "a".

result_screen1.png
Figure 6

Cover the light sensor on the IO Xplained Pro board (by placing your hand over it) to print the temperature on the terminal and remove the hand. Repeat this step to continue printing the temperature on the terminal.

result_screen2.png
Figure 7

You should see the temperature values (in °F) getting printed on the terminal when the light sensor is covered, as shown above.

Step 7.2: Observe Current Consumption on Data Visualizer

Data Visualizer is a program to process and visualize data. The Data Visualizer can receive data from various sources such as the Embedded Debugger Data Gateway Interface (EDBG DGI) and COM ports. It is possible to track an application in run-time using a terminal graph or oscilloscope. It analyzes the power consumption of an application through a correlation of code execution and power consumption when used together with a supported probe or board.

Download and install the stand-alone Data Visualizer.

Before measuring the power consumption, power on reset the device and select the Power Measurement Mode by entering option "a" on the Serial terminal.

1

Open the Data Visualizer application from your PC and select the connected Power Debugger Data Gateway board on the DGI Control Panel, then click on Connect. The Data Visualizer will then start searching for protocols from the Power Debugger board.

data_visualizer_dgi_control_panel_selection.png
Figure 8

2

Once the Data Visualizer is connected to the Power Debugger, different interfaces will appear. Select the Power interface and click on the Start button to start measuring the power consumption of the device.

data_visualizer_power_start_buttons.png
Figure 9

Ensure that the hardware setup is connected as mentioned in the Hardware Setup on the launch page.

On the right-hand side of the Power Analysis window, click on the Control Panel tab and disable Channel B.

data_visualizer_power_analysis_window.png
Figure 10

3

Figure 11 shows the device in Standby mode with its measured power consumption. You can observe small peaks that illustrate the 500 milliseconds Real-Time Clock (RTC) timer expiry.

device_in_standby_mode.png
Figure 11

The average value is considered when measuring the power consumption of the device because the instant value is not stable. Then, the power consumption of the device in Standby mode is 11.4 µA.

4

Cover the light sensor on the I/O1 Xplained Pro board by placing your hand over it (or another element) to print the temperature on the terminal and observe the power consumption of the device.

device_wakes_up_and_print_temperature.png
Figure 12

The power consumption of the device in Active mode is 11.3 mA and the power consumption of the same device in Standby mode is 10.5 µA. This shows the device in Standby mode will consume less power.

The message is printed on the serial terminal when you have done this step.

result_screen3.png
Figure 13

5

Press the SW0 button to switch from Standby mode to Idle mode. Figure 14 shows the transition of the power consumption from Standby Sleep mode to Idle Sleep mode.

active_idle_transition.png
Figure 14

The power consumption of the device in Standby Sleep mode is in µA and the power consumption of the same device in Idle Sleep mode is ~2.7 mA. This shows the device in Idle Sleep mode will consume a little higher power than Standby Sleep mode.

The message is printed on the serial terminal when you have done this step.

result_screen4.png
Figure 15

6

Place your hand close to the light sensor. The device wakes up, reads, and prints temperature values on the serial console, and re-enters the Standby mode. Figure 16 shows the transition power consumption values from Idle to Standby mode.

device_idle_to_standby_mode.png
Figure 16

The message is printed on the serial terminal when you have done this step.

result_screen5.png
Figure 17

Figure 18 shows the device in Idle mode with a measured power consumption of 2680 µA.

device_in_idle_mode.png
Figure 18

You can observe that the small peaks coming from RTC timer expiry disappeared because the power consumption in Idle mode is higher than the power required to start AC conversion.

Note that the above results highlight that the power consumption is lower in Standby mode than in Idle mode.

Step 7.3: Wake-up Time Measurement Using Logic Analyzer/ Cathode-Ray Oscilloscope (CRO)

To demonstrate the CPU wake-up time, switch SW0 is configured to generate an interrupt. A General Purpose Input/Output (GPIO) is toggled in the Interrupt Service Routine (ISR) of the switch press event. The MCU comes out of Sleep mode when an interrupt occurs (in this case, the switch press interrupt). The time between the switch press and the GPIO toggle in the ISR is the wake-up time.

Before measuring the Wake-up Time, power on reset the device and select the Wake-up Time Measurement mode by entering option "b" on the Serial terminal.

1

Connect your Logic Analyzer or your CRO to the board as mentioned in Hardware Setup on the Launch Page.

2

Now, press the SW0 switch and capture the signals to measure the wake-up time from Standby Sleep to Active.

Figure 19 shows the wake-up time for the device Standby Sleep mode to Active mode:

wakeup_time_from_standby.png
Figure 19

The message is printed on the serial terminal when you have done this step.

result_screen6.png
Figure 20

Press the SW0 switch and capture the signals to measure the wake-up time from Idle Sleep to Active.

Figure 21 shows the wake-up time for the device Idle Sleep mode to Active mode:

wakeup_time_from_idle.png
Figure 21

The message is printed on the serial terminal when you have done this step.

result_screen7.png
Figure 22

When you repeat the switch SW0 pressing, the device sleep state will switch between Standby to Idle and Idle to Standby.

The message printed on the serial terminal when you have done this step.

result_screen8.png
Figure 23

By observing the outputs, you can conclude that the wake-up time is greater in Standby mode than in Idle mode.

 Results

You successfully created a low-power application using the SAM D21 Xplained Pro Evaluation Kit and I/O1 Xplained Pro Kit and experienced how, where, and which Low Power mode to use depending on the application requirements such as power and wake up response times.

 Analysis

In this lab, you have successfully created a project from scratch, added Peripheral Libraries (PLIBs), and learned how to use an Event System to drive events received from the peripherals without CPU intervention. You also learned how to configure a device to work in Sleep modes and measure wake-up time.

 Conclusions

In this tutorial, you discovered how to configure the device to work in Sleep modes. This tutorial can be used as a reference when you develop a real-time application where the power and wake up response time play crucial roles.

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