Low Power Application on SAM D21 Using Harmony v3 Peripheral Libraries: Step 7
Contents
- Build and Program the Application
- Observe Current Consumption on Data Visualizer
- Wake-up Time Measurement Using Logic Analyzer/ Cathode-Ray Oscilloscope (CRO)
- Results
- Analysis
- Conclusions
Build and Program the Application
Clean and build your application by clicking on the Clean and Build button.
Program your application to the device by clicking on the Make and Program button.
Open the Tera Term application (or another terminal console) on your PC and navigate to File > New connection.
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.
Open the Serial port configuration of Tera Term by navigating to Setup > Serial port.
In the Serial Port window, verify that the Baud rate is set to 4800 and other elements are set as shown in the accompanying image, then press OK.
Now that the serial console is configured, reset the board, and verify the application displayed the Measurement Menu along with the application title message.
Select the Power Measurement Mode by entering option "a".
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.
You should see the temperature values (in °F) getting printed on the terminal when the light sensor is covered, as shown in the accompanying image.
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.
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.
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.
On the right-hand side of the Power Analysis window, click on the Control Panel tab and disable Channel B.
The accompanying image 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.
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.
The message is printed on the serial terminal when you have done this step.
Press the SW0 button to switch from Standby mode to Idle mode. The accompanying image shows the transition of the power consumption from Standby Sleep mode to Idle Sleep mode.
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.
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. The accompanying image shows the transition power consumption values from Idle to Standby mode.
The message is printed on the serial terminal when you have done this step.
The accompanying image shows the device in Idle mode with a measured power consumption of 2680 µA.
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.
Connect your Logic Analyzer or your CRO to the board as mentioned in Hardware Setup on the Launch Page.
Now, press the SW0 switch and capture the signals to measure the wake-up time from Standby Sleep to Active.
The accompanying image shows the wake-up time for the device Standby Sleep mode to Active mode:
The message is printed on the serial terminal when you have done this step.
Press the SW0 switch and capture the signals to measure the wake-up time from Idle Sleep to Active.
The accompanying image shows the wake-up time for the device Idle Sleep mode to Active mode:
The message is printed on the serial terminal when you have done this step.
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.
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.
