As you know well, the embedded systems have successfully invaded human lives and already became part of our existence. We started carrying quite a few in our pockets, bags and everywhere. Clearly we have all permitted them to share our space because we find some utility in keeping them around. Portable systems give us freedom to move around places, managing tasks effectively and enable us to handle more than before. As a result, we prefer to have portable systems rather than solutions coming with a power cord. As the embedded system designer, you need a better skill set to manage this kind of new generation portable systems. Here we see how to upgrade our skill set to meet the challenges of getting ready next generation portable embedded systems.
Select right microcontroller for the task.
When you start designing anything as a portable application, your first design step is to zero in on the right target microcontroller. You need to find a micon giving the maximum performance with least possible operating power. So far in all your applications, you might have divided the total application into many manageable tasks and allocate micon and peripheral resources to each of these tasks keeping an eye on the time limitations. Now, for the portable systems, you need to define an operating condition for these tasks taking the available voltage from the system battery into account. As you know well, the battery power output conditions can get uncertain without any notice and most of the time, batteries surprise you in unpleasant ways. Another issue you should take into account is that the system staying in a silent state or waiting for some event or user interaction for a good amount of time in its usage. Next you need to decide the right operating frequency for each of these tasks to extract maximum juice out of your selected battery. If you let your controller run at the maximum rated clock, then your hardware starts consuming more power and end up draining battery super fast. You need to find out the possibility of managing that task with lesser frequency at a lowest operating voltage. If you take these two factors into your design philosophy, you can easily enhance the battery running time to a great extend. To emphasize the above points, when you reduce the operating voltage to its 80% of the value, you can note the power consumption going down to 64% of its original value. Likewise when the operating frequency goes down, micon’s dynamic power consumption becomes less than before.
Manage peripheral functions effectively.
You need to control power consumption of unused peripheral functions for the given tasks to conserve more operating power. You can further reduce power when you can stop the clock sources to these peripherals.
A matching microcontroller for your solution.
With the right microcontroller, your efforts can be minimized and you need to ensure that the following facilities are available from your choice: The microcontroller should be running for a wide variation of supply voltage as the first and foremost feature. As the next step,you should have ways and means of changing the operating clock dynamically for your defined tasks. Most important is the versatile integration of all the required peripheral functions within the micon itself. You already know having more usable peripherals inside the micon can drive the power consumption southward and most of the latest controllers have them in plenty. But keeping a dynamic clock generating mechanism inside is more useful. Built in clock sources reduce power consumption significantly. Then you need onboard comparators to keep track of battery voltage all the time to take the appropriate actions. Only with this facility, you can add sensitivity with your application for the varying battery voltage. Proper reset circuits complement these voltage detection facilities. Having all these functions inside of the micon itself gives you a distinctive advantage when designing any portable system.
Available choices to you in microcontrollers: These days you get plenty of useful features with every controller. But you need to check carefully to derive best utility out of them. RL78 family of 16 bit microcontrollers manufactured by Renesas is the popular series most suitable for battery based portable solutions. For most of your applications, on chip facilities of this family are most suitable.
We get ready to introduce this controller in forthcoming articles. Stay tuned for more useful design news….