本帖最后由 瘦网虫 于 2013-7-2 14:03 编辑
这个问题与本系列中前几个问题有一丁点的联系。
如果你遇到了你的arduino程序莫名不能运行，莫名重启，莫名的问题，
可以简单浏览下此贴，说不定这就是你的菜。
内存不够，内存溢出，内存没法再释放了，程序精简到不能再精简了，如果还不能搞定arduino内存不够用，来试试这个。
PROGMEM
这个干什么用？它可以帮你把放在ram里面的变量，存到flash上面去，释放出你可怜的内存。
比如：
你原来这样定义，放到ram中，占用内存宝贵的6个字节。
- unsigned int charSet[] = {1,2,3};
改成这样：放到flash中，占用廉价的flash6个字节，释放出内存6个字节。
- PROGMEM prog_uint16_t charSet[] = { 1,2,3};
然后再读出来放到ram里面来运行。
这样的6个字节看起来没节省什么空间是吗？
- unsigned int charSet[] = {1,2,3};
那这样的呢？能省很多了吧。。
- PROGMEM unsigned int rawCodes_ac_open[200] = {4397,4368,561,1578,560,537,557,1581,584,1582,584,486,558,537,584,1554,560,538,558,510,558,1607,557,513,585,511,556,1585,581,1583,583,486,557,1609,556,513,558,538,557,512,558,1607,558,1583,557,1608,558,1608,557,1580,559,1606,559,1581,556,1609,557,512,559,537,558,512,557,539,557,512,558,1607,558,1582,558,537,584,1555,558,1607,556,514,559,537,556,513,558,537,556,514,558,1606,559,511,583,513,558,1582,557,1608,558,1580,585,5154,4419,4347,584,1555,558,539,557,1581,584,1581,571,501,577,516,571,1568,557,541,581,487,557,1608,557,513,558,538,557,1582,583,1582,584,487,557,1608,557,511,611,486,558,510,558,1607,557,1609,556,1583,583,1582,583,1555,558,1607,558,1607,559,1582,557,537,585,486,558,510,558,540,558,509,557,1608,558,1608,557,512,559,1606,559,1581,558,537,581,490,558,510,587,511,557,511,559,1606,559,510,569,527,558,1582,560,1604,561,1605,561};
还可以更多的
看看官方的reference:
http://www.arduino.cc/en/Reference/PROGMEM
要想省内存出来，就需要2步，一步写到flash，一步从flash读出来。
看看例子，其实不难。下面看看支持哪些，
不支持float型哦...不支持float型...不支持..不.....支持
prog_char - a signed char (1 byte) -127 to 128
prog_uchar - an unsigned char (1 byte) 0 to 255
prog_int16_t - a signed int (2 bytes) -32,767 to 32,768
prog_uint16_t - an unsigned int (2 bytes) 0 to 65,535
prog_int32_t - a signed long (4 bytes) -2,147,483,648 to * 2,147,483,647.
prog_uint32_t - an unsigned long (4 bytes) 0 to 4,294,967,295
下面是一段读写的例子
//保存一些 unsigned ints
PROGMEM prog_uint16_t charSet[] = { 65000, 32796, 16843, 10, 11234};
// 或者保存一些chars
prog_uchar signMessage[] PROGMEM = {"I AM PREDATOR, UNSEEN COMBATANT. CREATED BY THE UNITED STATES DEPART"};
unsigned int displayInt;
int k; //k在这里类似于i，你要自己循环增加
char myChar;
// 读回来一个 2-byte 的 int
displayInt = pgm_read_word_near(charSet + k)
// 读回来一个 char
myChar = pgm_read_byte_near(signMessage + k);
Enjoy your free ram~
解决问题系列（4）——红外编码分析利器使用
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发表于 2013-7-2 13:40:27
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