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POAvoid creating multiple copies of code in memory
 

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    <p>I'm new to developing on embedded systems and am not used to having very little program memory (16kB in this case) to play with. I would like to be able to create global variables, arrays, and functions that I can access from anywhere in the program while <em>only existing in one place</em> in memory. My current approach is to use static class members and methods that I can use by simply including the header file (e.g. <code>#include "spi.h"</code>).</p> <p>What is the best approach for what I'm trying to do?</p> <p>Here is an example class. From what I understand, variables such as <code>_callback</code> and function definitions like <code>call()</code> in the .cpp will only appear in spi.o so they will appear only once in memory, but I may be mixed up.</p> <p><strong>spi.h:</strong></p> <pre><code>#ifndef SPI_H_ #define SPI_H_ #include "msp430g2553.h" class SPI { public: typedef void (*voidCallback)(void); static voidCallback _callback; static char largeArray[1000]; static __interrupt void USCIA0TX_ISR(); static void call(); static void configure(); static void transmitByte(unsigned char byte, voidCallback callback); }; #endif /* SPI_H_ */ </code></pre> <p><strong>spi.cpp:</strong></p> <pre><code>#include "spi.h" SPI::voidCallback SPI::_callback = 0; char SPI::largeArray[] = /* data */ ; void SPI::configure() { UCA0MCTL = 0; UCA0CTL1 &amp;= ~UCSWRST; IE2 |= UCA0TXIE; } void SPI::transmitByte(unsigned char byte, voidCallback callback) { _callback = callback; UCA0TXBUF = byte; } void SPI::call() { SPI::_callback(); } #pragma vector=USCIAB0TX_VECTOR __interrupt void SPI::USCIA0TX_ISR() { volatile unsigned int i; while (UCA0STAT &amp; UCBUSY); SPI::call(); } </code></pre>
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    1. COto simply include the header and start using the "SPI" just use [Singleton pattern](http://stackoverflow.com/questions/1008019/c-singleton-design-pattern) , it is a common in embedded that you have one peripheral and only one object to deal with hardware no more objects allowed. , also you may use [factory pattern](http://stackoverflow.com/questions/5120768/how-to-implement-the-factory-pattern-in-c-correctly) to allow for example a certain number of objects (SPI channels)
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      1. USAbdurahman
 

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