Embedded development: seven techniques for estimating battery life

　　 In our modern mobile society , One of the biggest complaints about electronic devices is that their batteries are not as long as expected , Humans must be somewhat obsessed with our ability to always remain connected and transmit data in one form or another . The increasing use of mobile devices has not only forced chip makers to reconsider how they design microcontrollers , It even leads embedded system designers to build systems , Even embedded developers with the latest technologies and technologies can hardly ensure that they have enough batteries to run their products at the expected time intervals . Seven tips can be followed to help ensure accurate battery life estimates .

　　 skill 1– Traditional battery budget analysis

　　 The first step for engineers to estimate the battery , Usually the last step , Is to create a traditional battery budget . This type of analysis usually involves creating a spreadsheet , It lists each component in the system . then , The engineer inspects each component , Determine minimum 、 Typical and maximum current draw and record . I have this information , Engineers can now begin to estimate the percentage of time the system is in each consumption bin . for example , The microcontroller may only have 5% Time in running mode ,25% Time in low power stop mode ,70% Time in deep sleep mode .

　　

 

　　 After analyzing each component in this way , Add up the results , The system now has a minimum 、 Typical and maximum current consumption data , Can be used to determine the size of the battery . Part of the problem with most such analyses is , These figures are more or less based on experience . let me put it another way , They are all speculation . The engineer did his best to guess , But there is usually a certain degree of uneasiness , Because there may be unexpected leakage current , Error estimation of the actual power consumption of the microcontroller , And many other factors .

　　 skill 2– Software RMA

　　 As part of software architecture design and analysis , Monotonic rate analysis shall be performed on the software (RMA). This analysis will not only identify the different tasks that the software will perform , It also gives the relative concepts of how long each task will run and the different peripherals involved . From this information , A simple list of different tasks and behaviors of the microcontroller can be recorded , To improve the traditional battery budget guess ( Guess ). Please note that ,RMA It also reassures embedded developers , All tasks will be completed in a certain way , Don't miss the deadline .

　　

 

　　 skill 3– Chip supplier tools

　　 Microcontroller is one of the most fuzzy areas in energy consumption . About how these little guys will burn energy , There are too many variables . A review of most supplier data sheets will be provided based on temperature 、 voltage 、 Peripheral settings 、 At an altitude of 、 The wind speed 、 Large scale energy consumption of developers' constellations, etc . There's always a problem , Where and how did these figures come from , Are they accurate .

　　 Even if it's just a wave , Chip manufacturers have also begun to provide some new tools to developers , These tools will greatly improve the way battery budgets are estimated .

　　 skill 4– Bench experiment

　　 Just as any engineer likes modeling and evaluation tools , Before those assumptions are tested and proven on the workbench , There is always a sense of tension . This is why the real behavior of the development suite and prototype components must be tested early in the design cycle ! It doesn't need to be a clean and tidy test , But at least you should be able to test about software 、 Basic assumptions about microcontroller power consumption and other components on the system .

　　 One of the benefits of benchmarking is , It is a fast and cheap way to prove the right direction of low power design . If there is an error in the data book , There are omissions in assumptions, etc , Then the data obtained from the workbench can be used to improve the model . The end result is a step closer to proving that the intended design is actually effective .

　　 skill 5– Battery life cycle analysis

　　 Creating models 、 Benchmarking and simulating the energy consumption of the system is very helpful to determine the battery life of the embedded system . However , As far as the battery itself is concerned , There are still some different pitfalls . The first problem relates to rechargeable batteries , I.e. each charge / The discharge cycle will reduce the total capacity of the battery . The result of this capacity reduction is , The device may have a battery life of nine hours when it is first manufactured , But six months later it may only last six hours . This is a factor that embedded developers need to consider when estimating battery capacity .

　　 The second factor to keep in mind is the peak current consumption of the embedded system . The rated operating current of any battery is a certain number of milliampere hours , But when the battery is partially discharged , Peak current may cause the battery voltage to drop or fall below undervoltage . As a result, , Before the battery really releases all its energy , Embedded systems are dead .

　　 skill 6—— Compiler vendor tools

　　 Once the battery life analysis reaches the benchmark stage , There are some very exciting compiler related tools available to validate system assumptions . These tools can monitor the system in 200 kHz How much energy is used at frequency ! What's better is , They allow the current consumption of the system to be correlated with the code being executed !

　　

 

　　 With such tools , Developers can view the configuration file , Determine which tasks or functions consume the most energy from the battery , And low power optimization in these aspects ! There are even tool options to keep track of which functions take how much execution time , In this way, the developer can determine which function or task occupies CPU!

　　 skill 7—— Get a second opinion

　　 Especially when a development cycle or product release is in danger or critical to the survival of a company , Getting a second pair of eyes is very useful . Whether colleagues or third parties , Having another engineer review the estimates and data will generate information and ideas that embedded developers may not have thought of , It helps enormously to ensure that nothing narrows through , And as the product release date approaches , Engineers and teams are confident that the system will not run out of energy ahead of time .v