Otii of Qoitech allows a quick and easy analysis and comparison of power measurements
Poor battery life affects the recording of too many devices. How can energy be analyzed so thoroughly that products meet consumer expectations?
One of the technical reasons that limits the acceptance of the products of the Internet of Things (IoT) is the low battery life. So how can the power consumption of an embedded system be analyzed and optimized in sufficient detail to achieve “reasonable” autonomy?
According to Vanja Samuelsson, founder of Qoitech, a Swedish start-up from Sony, “There is a gap in the market for an affordable IoT-enabled development tool.” “IoT is extremely complex and many people create new technologies. solutions. inexperienced.
“Although power has always been critical, these devices require hardware layers to work in hardware, which means that choosing the wrong protocol or ignoring the impact of software updates can hurt the overall user experience. ”
Performance measuring tool
“For greater simplicity, Qoitech has developed Otii, which enables quick and easy analysis and comparison of performance metrics, and provides a clear link between measurement and code execution, providing an integrated method for automated measurement and testing.” says Samuelsson,
With its Arc hardware and associated cross-platform desktop application, Otii enables embedded software developers to optimize their applications, while hardware developers can make informed decisions when choosing their conversion components power and battery management.
“For low-power embedded systems, the choice of SoC or MCU may be the most important, and semiconductor manufacturers have chosen many energy-saving solutions, sometimes in conjunction with a DMA (Direct Memory Access) controller. ). without the processor needs to be active, but it’s hard to judge the single microcontroller sheet, “says Samuelsson.
Another challenge is the stabilization of the oscillator after waking up. A peripheral clock using a crystal takes time to stabilize before the processor can start processing the instructions after it wakes up. If a phase locked loop (PLL) is included, possibly providing higher clock rates, the lock will also take time, requiring additional time. Different microcontrollers offer different solutions and the one that offers the lowest energy consumption is usually found in parts experience, partial happiness.
The Otii Arc is a unique hardware component that provides a programmable power source, extended dynamic range current measurement and additional channels for side measurement and data acquisition.
By controlling the supply voltage while measuring power consumption, different power source strategies can be evaluated. If the influence of the subcircuits has to be understood, the differential analog input on the extension port, combined with a low resistance in the supply line, allows a clear separation of the influence of the energy consumption. total.
According to Samuelsson, the second key element is the serial port data entry of the expansion port. Serial communication data can be acquired via this interface at rates of 9600 bits per second (bps) up to 4 Mbps. All log messages issued by the application are then timestamped and synchronized with other time domain metrics. An application based on a real-time operating system (RTOS) could be followed with instrumented trace logging via a UART as it moves from one task to another outside of its inactive modes and low consumption. The last element is the unbalanced analog input, available when no differential power measurement is performed.
This can be used to capture an analog or digital signal in order to monitor a single general purpose input / output pin (GPIO).
Above: an example of pulse discharge characteristics
“The Otii software makes it easy to analyze power consumption, divided into three sections, a sidebar for configuring records and visualizations, a chart area, and a log view,” says Samuelsson.
To easily understand the relationship between power consumption and application execution, graphical views and log views are linked. The minimum, maximum, average, and energy measurements are also automatically updated when the selected range or measurement point is moved. The search function in serial output log data makes it easy to find key moments in the execution of the application.
Since IoT nodes can not operate in direct sunlight, power measurements for multiple nodes are often required simultaneously. In some mesh configurations, some devices may act as gateways, resulting in higher power consumption than a device that simply acts as a node.
Otii software makes it possible to differentiate several connected Otii Arc tools and even to give the user individual names, which guarantees ease of use to quickly switch between the different hardware components to be measured.
Other advanced features include battery cell simulation and scripting support. The built-in battery simulator allows you to select one of the different battery types rather than set a fixed supply voltage. For each selected battery, the most important parameters are displayed along with the manufacturer’s discharge curve. Using a slider, the developer can also determine the discharge height of the cell, which is ideal for understanding the response of an application to the voltage drop that occurs in the last 10-20% of the lifetime a battery.
Thanks to the standard Lua language, serial data can be imported from log files captured outside the Otii software.
“If these log files contain timestamp information, you can convert them to Otii format for import into the GUI,” Samuelsson explains.
Two sample scripts are provided to manage the protocols of the Android ADB or Linux kernel. Scripts are also available in the installation folder to be used as a base for modified scripts. If the time interval for performance metrics and log files does not match, the log view also provides an option to apply a positive or negative shift in milliseconds so that data can be quickly synchronized with the performance metrics logs. .
The profiling of the battery can also be done using scripts.
The data sheet of a cell manufacturer offers a combination of constant discharge, constant discharge and pulsed discharge discharge curves, usually at or near room temperature. Since it is unlikely that the application of the developer will closely match these standard discharge characteristics, a manual test may be performed.
These tests consist of a loop that applies different loads for different periods of time as the cell voltage is recorded.
“The test can be stopped either when a certain number of iterations are reached, or when the cell voltage has reached a lower limit,” says Samuelsson.
Towards the end of product development, it is also wise to perform longer-term tests or even implement an automated test function. Here, the scriptability can be used in conjunction with running the Otii software via the command line interface. Hand-built test beams or even creative and test environments such as Jenkins can be used to initiate and monitor such tests.
“When it comes to product development for IoT, developers need the best knowledge of power consumption in every cycle of the development process, whether it’s
Otii Arc’s wide dynamic range hardware and Otii software – featuring a clean and simple interface – have been designed to handle high energy usage times with specific areas of application code, microcontroller configuration or SoC or subsystem switching. ,