Editing Embedded Programming Tips and Tricks for Beginners
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However care should be taken when using signed variables.<br> | However care should be taken when using signed variables.<br> | ||
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=Fast Multiplication= | =Fast Multiplication= | ||
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Doing this also increases the number of cycles needed to execute your functions as the variables needs to be loaded/unloaded every function call. On a low MHz micro with lots of small functions this can slow your code down. | Doing this also increases the number of cycles needed to execute your functions as the variables needs to be loaded/unloaded every function call. On a low MHz micro with lots of small functions this can slow your code down. | ||
− | + | Therefor, in small-scale embedded programming, it's perfectly acceptable to use global variables when the information is something most of your program needs access to. | |
It's a balancing act to decide if a variable is something that should be passed to a function or available to every function as a global variable. Usually however, it is quite obvious. | It's a balancing act to decide if a variable is something that should be passed to a function or available to every function as a global variable. Usually however, it is quite obvious. | ||
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==The Equals Sign== | ==The Equals Sign== | ||
− | One of the most common mistakes | + | One of the most common mistakes new (and old) programmers make in C is the following. |
<pre> | <pre> | ||
if (MyVariable=5) | if (MyVariable=5) | ||
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} | } | ||
</pre> | </pre> | ||
− | The mistake here is the single equals sign. A single equals sign is used for doing an 'assignment' | + | The mistake here is the single equals sign. A single equals sign is used for doing an 'assignment' eg MyVariable=5 <br> |
+ | In the example above we want to do a 'comparison/relation' to produce a true/false answer for the if statement. | ||
+ | The operator for this is double equals. | ||
− | + | So the corrected code is | |
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<pre> | <pre> | ||
if (MyVariable==5) | if (MyVariable==5) |