A technology company is developing a new fitness tracker. The tracker is worn on the wrist and monitors the wearer's heart rate, the number of steps taken and their sleep. It has a rechargeable battery and a touch screen.
Discuss the use of embedded systems in the fitness tracker.
Your answer should include:
- what an embedded system is.
- the functions embedded systems perform in the tracker.
- why an embedded system is suitable for this device.
Mark scheme
Indicative content
What an embedded system is
- An embedded system is a computer system that forms part of a larger device, such as the fitness tracker.
- It performs a single, dedicated or specific task rather than being a general purpose computer.
- It is often built around a microcontroller, which contains the processor, RAM and ROM on a single chip.
- Its software is held in ROM so the tracker can run its program as soon as it is switched on.
Functions in the tracker
- Monitoring the heart rate using a sensor and processing the readings so that they can be displayed on the screen.
- Counting steps using an accelerometer and using the count to calculate the distance walked or the calories burned.
- Tracking sleep by monitoring the wearer's movement during the night.
- Controlling the touch screen so that the user can move between displays.
- Managing the battery, for example stopping the charging when the battery is full and saving power when the tracker is idle.
- Sending the collected data to a smartphone using Bluetooth so that it can be viewed in an app. Accept any other specific function of the fitness tracker that an embedded system could control.
Why an embedded system is suitable for this device
- It has low power consumption, so the battery lasts longer between charges, which matters for a device that is worn all day.
- It is small and light, so it can be fitted into a wristband.
- Its dedicated function means it does not need a full operating system, so it is reliable and does not need restarting.
- The program is small and stored in ROM, so the tracker needs only a small amount of memory.
- It can be optimised for its specific tasks, so it responds quickly to the readings from its sensors.
- The low cost per unit keeps the tracker affordable for the customer.
Levels
- Level 0 (0 marks): No rewardable content.
- Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
- Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
- Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)
Additional guidance
- Level 3 responses must cover what an embedded system is, the functions it performs in the tracker and why it is suitable for the tracker.
- Do not award installing new software/apps, functions the tracker does not perform (such as playing music) or 'it is like a phone'.
Example answers and how they were marked
An embedded system is a computer system that forms part of a larger device and performs a single, dedicated task. In the tracker it is built around a microcontroller, which has the processor, RAM and ROM on one chip, and its program is stored in ROM so it runs as soon as the tracker is switched on. The embedded system monitors the heart rate using a sensor and processes the readings before showing them on the screen. Another function counts the steps using an accelerometer and uses that count to work out the distance walked and the calories burned, and further functions monitor movement at night to track sleep and send the data to a smartphone by Bluetooth. The embedded system also controls the touch screen and manages the battery so that charging stops when it is full and power is saved when the tracker is idle. An embedded system is suitable because it has low power consumption, so the battery lasts longer between charges, which matters for a device that is worn all day and cannot be charged constantly. It is also small and light, so it fits into a wristband, and because it is dedicated to a few tasks it does not need a full operating system, so it is reliable and can be optimised to respond quickly to its sensors. Keeping the cost low also makes the tracker affordable for the customer.
Why: Comprehensive definition including the microcontroller and ROM (AO1), a range of functions each applied to the tracker (heart rate, steps, sleep, Bluetooth, touch screen, battery), and suitability points developed with reasons (low power for a device worn all day, small size for a wristband, dedicated design for reliability and quick response). Sustained lines of reasoning, all three bullets covered: Level 3 (5-6) clearly met.
An embedded system is a small computer inside a device. In a fitness tracker it can monitor your heart rate and count your steps. It is suitable because it is small and does not use much power.
Why: Basic independent points only: a basic definition, two functions and one basic suitability point, with no development and almost no application to the tracker (no explanation of why small size or low power matter). Level 1 (1-2 marks), upper end because there are several independent correct points, but no linkage or reasoning for Level 2.
An embedded system is a computer that you can install apps on. The fitness tracker uses it to play music and send texts. It is suitable because it is like a phone.
Why: The definition is the opposite of an embedded system (it cannot install new software), the functions are ones the tracker does not perform and 'it is like a phone' is not a suitability point. No rewardable content: Level 0 (0 marks).