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【嵌入式】强行写GPIO实现I2C通讯,控制SSD1306显示屏显示图像

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2014-1-26
发表于 2017-11-19 09:59:26 | 显示全部楼层 |阅读模式

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SSD1306显示屏的PDF文档:https://cdn-shop.adafruit.com/datasheets/SSD1306.pdf

这玩意儿是一个128x64分辨率(其实它有三种规格,我买的是这种)、单色、自带显存的玩意儿。它的接口有很多种,我买的是封装成i2c接口的。
控制它显示的原理很简单:开屏,写显存。完事儿。写显存后它就会立即把效果显示出来。当然它自己是有个刷新率的,会以一定频率不断读取显存并使用屏幕显示。
除了显存,它还有各种控制寄存器。和之前的用i2c操作MPU6050的情况不同,用i2c操作SSD1306的方式分为两种:

1、写命令
2、写显存

其中写命令的方式,PDF文档描述得不是很清楚,而官方资料居然是C艹的,它写了个C艹的类用于维护SSD1306,令人恼火。
不过这个C艹的资料也还算好懂。经过一次次尝试我知道了它是如何写命令和写显存的了。

写命令的方式:
1、开始条件。这个和之前的例子一样,最初SDA和SCL都是高电平,然后先拉低SDA,再拉低SCL。
2、写入芯片地址,以及R/W位。控制SSD1306不存在读取的过程,所以R/W位设为0,也就是低电平——写入。
3、从SSD1306读取ACK状态。不过SSD1306的SDA输出的pin不一定和I2C总线相连,所以它也可能不回应ACK。
4、写入控制字节。第7 bit是Continuation bit,不管它,写0。第6 bit是“命令/数据”bit,值为1的时候是写显存,值为0是写命令。其余位都是0。所以这次写入的控制字节其实是0。
5、读取ACK。
6、写入命令。
7、读取ACK。
8、结束条件:先拉高SCL,再拉高SDA。

当一个命令带有参数的时候,你要先用一次这种写命令的过程写入你的命令字节,再用一次这种写命令的过程写入你的命令参数。

写显存的方式:
1、开始条件。
2、芯片地址。
3、读取ACK。
4、写入控制字节。因为是写显存操作,这次写入的控制字节是0x40。
5、读取ACK。
6、写入你要写进显存的值。你写入后,它自己会把写显存的指针往后移,移动到结尾后又会归位到起始处。
7、读取ACK。
8、回到第6步。嗯其实这是个循环,你可以在此完成批量的写显存的操作,想写几个字节就写几个字节。
9、结束条件。

写显存的过程受到多个控制寄存器的影响。按照我这次写的代码对其进行的初始化的情况来看,你写入的一个字节,会成为它的显示指针所在的当前位置向下8个像素的状态值。然后它的显示指针是往右移动1个字节的。显示指针移动到最右后,又会自动移回最左,然后往下移动8个像素。这种设计,是为了便于让你通过直接写显存的方式来让它一行行地输出8个像素高的点阵字体。
不过你也可以把SSD1306_MEMORYMODE设为1(先发送命令“SSD1306_MEMORYMODE”(值为0x20),再发送命令“1”),来让它改变显示指针的移动行为——之前是向右移动1个像素,现在是向下移动8个像素。然后就可以构成一个从顶到下为x轴,从左到右为y轴的单色位图了。

这次的测试发现_i2c_delay()里面的usleep非常影响I2C的传输效率,它延迟的时长可能远超5us。估计和Bananapi M2的性能与时间片长度的设定有关。切走CPU会导致写入一整个显存要耗费接近1秒的时间。我把usleep(5)注释掉后,我发现它依然能完成通讯,并且显示屏的更新效率变得很高了。
  1. #include<stdio.h>
  2. #include<stdlib.h>
  3. #include<string.h>
  4. #include<stdarg.h>
  5. #include<inttypes.h>
  6. #include<wiringPi.h>
  7. #include<unistd.h>

  8. #define param_pins int scl_pin, int sda_pin
  9. #define i2c_pin scl_pin, sda_pin

  10. static void _i2c_delay()
  11. {
  12.         // usleep(5);
  13.         // 不用延迟它也能实现效果
  14.         // 用了延迟反而变得贼慢
  15. }

  16. static void _i2c_start(param_pins)
  17. {
  18.         pinMode(scl_pin, OUTPUT);
  19.         pinMode(sda_pin, OUTPUT);
  20.        
  21.         // start condition
  22.         digitalWrite(scl_pin, HIGH);
  23.         _i2c_delay();
  24.         digitalWrite(sda_pin, HIGH);
  25.         _i2c_delay();
  26.         digitalWrite(sda_pin, LOW);
  27.         _i2c_delay();
  28.         digitalWrite(scl_pin, LOW);
  29.         _i2c_delay();
  30. }

  31. static void _i2c_stop(param_pins)
  32. {
  33.         pinMode(scl_pin, OUTPUT);
  34.         pinMode(sda_pin, OUTPUT);
  35.        
  36.         digitalWrite(scl_pin, LOW);
  37.         digitalWrite(sda_pin, HIGH);
  38.         _i2c_delay();
  39.         digitalWrite(scl_pin, HIGH);
  40.         _i2c_delay();
  41. }

  42. static void _i2c_send_bit(param_pins, const int value)
  43. {
  44.         digitalWrite(sda_pin, value ? HIGH : LOW);
  45.         digitalWrite(scl_pin, HIGH);
  46.         _i2c_delay();
  47.         digitalWrite(scl_pin, LOW);
  48.         _i2c_delay();
  49. }

  50. static int _i2c_read_bit(param_pins)
  51. {
  52.         int received;
  53.         digitalWrite(scl_pin, HIGH);
  54.         _i2c_delay();
  55.         received = digitalRead(sda_pin) == HIGH ? 1 : 0;
  56.         digitalWrite(scl_pin, LOW);
  57.         _i2c_delay();
  58.         return received;
  59. }

  60. static int _i2c_read_byte(param_pins)
  61. {
  62.         int received = 0;
  63.        
  64.         pinMode(scl_pin, OUTPUT);
  65.         pinMode(sda_pin, INPUT);
  66.        
  67.         received |= _i2c_read_bit(i2c_pin) << 7;
  68.         received |= _i2c_read_bit(i2c_pin) << 6;
  69.         received |= _i2c_read_bit(i2c_pin) << 5;
  70.         received |= _i2c_read_bit(i2c_pin) << 4;
  71.         received |= _i2c_read_bit(i2c_pin) << 3;
  72.         received |= _i2c_read_bit(i2c_pin) << 2;
  73.         received |= _i2c_read_bit(i2c_pin) << 1;
  74.         received |= _i2c_read_bit(i2c_pin);
  75.        
  76.         // send NACK
  77.         pinMode(sda_pin, OUTPUT);
  78.         _i2c_send_bit(i2c_pin, 1);
  79.         return received;
  80. }

  81. static void _i2c_write_byte(param_pins, const int value)
  82. {
  83.         pinMode(scl_pin, OUTPUT);
  84.         pinMode(sda_pin, OUTPUT);
  85.         _i2c_send_bit(i2c_pin, value & 0x80 ? 1 : 0);
  86.         _i2c_send_bit(i2c_pin, value & 0x40 ? 1 : 0);
  87.         _i2c_send_bit(i2c_pin, value & 0x20 ? 1 : 0);
  88.         _i2c_send_bit(i2c_pin, value & 0x10 ? 1 : 0);
  89.         _i2c_send_bit(i2c_pin, value & 0x08 ? 1 : 0);
  90.         _i2c_send_bit(i2c_pin, value & 0x04 ? 1 : 0);
  91.         _i2c_send_bit(i2c_pin, value & 0x02 ? 1 : 0);
  92.         _i2c_send_bit(i2c_pin, value & 0x01 ? 1 : 0);
  93. }

  94. #define BLACK 0
  95. #define WHITE 1
  96. #define INVERSE 2

  97. #define SSD1306_I2C_ADDRESS   0x3C  // 011110+SA0+RW - 0x3C or 0x3D
  98. // Address for 128x32 is 0x3C
  99. // Address for 128x64 is 0x3D (default) or 0x3C (if SA0 is grounded)

  100. /*=========================================================================
  101.     SSD1306 Displays
  102.     -----------------------------------------------------------------------
  103.     The driver is used in multiple displays (128x64, 128x32, etc.).
  104.     Select the appropriate display below to create an appropriately
  105.     sized framebuffer, etc.

  106.     SSD1306_128_64  128x64 pixel display

  107.     SSD1306_128_32  128x32 pixel display

  108.     SSD1306_96_16

  109.     -----------------------------------------------------------------------*/
  110.    #define SSD1306_128_64
  111. //   #define SSD1306_128_32
  112. //   #define SSD1306_96_16
  113. /*=========================================================================*/

  114. #if defined SSD1306_128_64 && defined SSD1306_128_32
  115.   #error "Only one SSD1306 display can be specified at once in SSD1306.h"
  116. #endif
  117. #if !defined SSD1306_128_64 && !defined SSD1306_128_32 && !defined SSD1306_96_16
  118.   #error "At least one SSD1306 display must be specified in SSD1306.h"
  119. #endif

  120. #if defined SSD1306_128_64
  121.   #define SSD1306_LCDWIDTH                  128
  122.   #define SSD1306_LCDHEIGHT                 64
  123. #endif
  124. #if defined SSD1306_128_32
  125.   #define SSD1306_LCDWIDTH                  128
  126.   #define SSD1306_LCDHEIGHT                 32
  127. #endif
  128. #if defined SSD1306_96_16
  129.   #define SSD1306_LCDWIDTH                  96
  130.   #define SSD1306_LCDHEIGHT                 16
  131. #endif

  132. #define SSD1306_SETCONTRAST 0x81
  133. #define SSD1306_DISPLAYALLON_RESUME 0xA4
  134. #define SSD1306_DISPLAYALLON 0xA5
  135. #define SSD1306_NORMALDISPLAY 0xA6
  136. #define SSD1306_INVERTDISPLAY 0xA7
  137. #define SSD1306_DISPLAYOFF 0xAE
  138. #define SSD1306_DISPLAYON 0xAF

  139. #define SSD1306_SETDISPLAYOFFSET 0xD3
  140. #define SSD1306_SETCOMPINS 0xDA

  141. #define SSD1306_SETVCOMDETECT 0xDB

  142. #define SSD1306_SETDISPLAYCLOCKDIV 0xD5
  143. #define SSD1306_SETPRECHARGE 0xD9

  144. #define SSD1306_SETMULTIPLEX 0xA8

  145. #define SSD1306_SETLOWCOLUMN 0x00
  146. #define SSD1306_SETHIGHCOLUMN 0x10

  147. #define SSD1306_SETSTARTLINE 0x40

  148. #define SSD1306_MEMORYMODE 0x20
  149. #define SSD1306_COLUMNADDR 0x21
  150. #define SSD1306_PAGEADDR   0x22

  151. #define SSD1306_COMSCANINC 0xC0
  152. #define SSD1306_COMSCANDEC 0xC8

  153. #define SSD1306_SEGREMAP 0xA0

  154. #define SSD1306_CHARGEPUMP 0x8D

  155. #define SSD1306_EXTERNALVCC 0x1
  156. #define SSD1306_SWITCHCAPVCC 0x2

  157. // Scrolling #defines
  158. #define SSD1306_ACTIVATE_SCROLL 0x2F
  159. #define SSD1306_DEACTIVATE_SCROLL 0x2E
  160. #define SSD1306_SET_VERTICAL_SCROLL_AREA 0xA3
  161. #define SSD1306_RIGHT_HORIZONTAL_SCROLL 0x26
  162. #define SSD1306_LEFT_HORIZONTAL_SCROLL 0x27
  163. #define SSD1306_VERTICAL_AND_RIGHT_HORIZONTAL_SCROLL 0x29
  164. #define SSD1306_VERTICAL_AND_LEFT_HORIZONTAL_SCROLL 0x2A

  165. #define stop_if_nack 1
  166. #define ignore_nack 0

  167. typedef struct ssd1306_i2c_ctrl_struct
  168. {
  169.         int sda_pin;
  170.         int scl_pin;
  171.         int chip_addr;
  172.         int check_ack;
  173. }ssd1306_i2c_ctrl_t, *ssd1306_i2c_ctrl_p;

  174. void ssd1306_i2c_init(ssd1306_i2c_ctrl_p inst, param_pins, const int chip_addr, const int check_ack)
  175. {
  176.         memset(inst, 0, sizeof *inst);
  177.        
  178.         inst->sda_pin = sda_pin;
  179.         inst->scl_pin = scl_pin;
  180.         inst->chip_addr = chip_addr;
  181.         inst->check_ack = check_ack;
  182. }

  183. int ssd1306_i2c_send_command(ssd1306_i2c_ctrl_p inst, const int command)
  184. {
  185.         int num_ack = 0;
  186.         const int sda_pin = inst->sda_pin;
  187.         const int scl_pin = inst->scl_pin;
  188.        
  189.         // start condition
  190.         _i2c_start(i2c_pin);
  191.        
  192.         // address & R/W bit (write => 0)
  193.         _i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
  194.        
  195.         // ACK
  196.         pinMode(sda_pin, INPUT);
  197.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  198.        
  199.         // control bvte
  200.         _i2c_write_byte(i2c_pin, 0x00);
  201.        
  202.         // ACK
  203.         pinMode(sda_pin, INPUT);
  204.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  205.        
  206.         // command
  207.         _i2c_write_byte(i2c_pin, command);
  208.        
  209.         // ACK
  210.         pinMode(sda_pin, INPUT);
  211.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  212.        
  213.         // stop condition
  214.         _i2c_stop(i2c_pin);
  215.         return num_ack;
  216. }

  217. int ssd1306_i2c_send_data(ssd1306_i2c_ctrl_p inst, const void *data, const size_t cb_data)
  218. {
  219.         int num_ack = 0;
  220.         const uint8_t *ptr = data;
  221.         size_t counter = cb_data;
  222.         const int sda_pin = inst->sda_pin;
  223.         const int scl_pin = inst->scl_pin;
  224.        
  225.         // start condition
  226.         _i2c_start(i2c_pin);
  227.        
  228.         // address & R/W bit (write => 0)
  229.         _i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
  230.        
  231.         // ACK
  232.         pinMode(sda_pin, INPUT);
  233.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  234.        
  235.         // control bvte
  236.         _i2c_write_byte(i2c_pin, 0x40);
  237.        
  238.         // ACK
  239.         pinMode(sda_pin, INPUT);
  240.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  241.        
  242.        
  243.         while(counter--)
  244.         {
  245.                 // data
  246.                 _i2c_write_byte(i2c_pin, *ptr++);
  247.                
  248.                 // ACK
  249.                 pinMode(sda_pin, INPUT);
  250.                 if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  251.         }
  252.        
  253.         // stop condition
  254.         _i2c_stop(i2c_pin);
  255.         return num_ack;
  256. }

  257. int ssd1306_i2c_fill(ssd1306_i2c_ctrl_p inst, const uint8_t val, const size_t cb_len)
  258. {
  259.         int num_ack = 0;
  260.         size_t counter = cb_len;
  261.         const int sda_pin = inst->sda_pin;
  262.         const int scl_pin = inst->scl_pin;
  263.        
  264.         // start condition
  265.         _i2c_start(i2c_pin);
  266.        
  267.         // address & R/W bit (write => 0)
  268.         _i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
  269.        
  270.         // ACK
  271.         pinMode(sda_pin, INPUT);
  272.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  273.        
  274.         // control bvte
  275.         _i2c_write_byte(i2c_pin, 0x40);
  276.        
  277.         // ACK
  278.         pinMode(sda_pin, INPUT);
  279.         if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  280.        
  281.         while(counter--)
  282.         {
  283.                 // data
  284.                 _i2c_write_byte(i2c_pin, val);
  285.                
  286.                 // ACK
  287.                 pinMode(sda_pin, INPUT);
  288.                 if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
  289.         }
  290.        
  291.         // stop condition
  292.         _i2c_stop(i2c_pin);
  293.         return num_ack;
  294. }

  295. int ssd1306_i2c_boot(ssd1306_i2c_ctrl_p inst)
  296. {
  297.         int num_ack = 0;
  298.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYOFF);
  299.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETDISPLAYCLOCKDIV);
  300.         num_ack += ssd1306_i2c_send_command(inst, 0xF0);
  301.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETMULTIPLEX);
  302.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_LCDHEIGHT - 1);
  303.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETDISPLAYOFFSET);
  304.         num_ack += ssd1306_i2c_send_command(inst, 0);
  305.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETSTARTLINE | 0);
  306.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_CHARGEPUMP);
  307.         num_ack += ssd1306_i2c_send_command(inst, 0x14);
  308.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_MEMORYMODE);
  309.         num_ack += ssd1306_i2c_send_command(inst, 0);
  310.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SEGREMAP | 0x1);
  311.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_COMSCANDEC);
  312.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETCOMPINS);
  313.         num_ack += ssd1306_i2c_send_command(inst, 0x12);
  314.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETCONTRAST);
  315.         num_ack += ssd1306_i2c_send_command(inst, 0xCF);
  316.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETPRECHARGE);
  317.         num_ack += ssd1306_i2c_send_command(inst, 0xF1);
  318.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETVCOMDETECT);
  319.         num_ack += ssd1306_i2c_send_command(inst, 0x40);
  320.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYALLON_RESUME);
  321.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_NORMALDISPLAY);
  322.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_DEACTIVATE_SCROLL);
  323.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYON);
  324.        
  325.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_COLUMNADDR);
  326.         num_ack += ssd1306_i2c_send_command(inst, 0);
  327.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_LCDWIDTH - 1);
  328.         num_ack += ssd1306_i2c_send_command(inst, SSD1306_PAGEADDR);
  329.         num_ack += ssd1306_i2c_send_command(inst, 0); // Page start address (0 = reset)
  330. #if SSD1306_LCDHEIGHT == 64
  331.         num_ack += ssd1306_i2c_send_command(inst, 7); // Page end address
  332. #endif
  333. #if SSD1306_LCDHEIGHT == 32
  334.         num_ack += ssd1306_i2c_send_command(inst, 3); // Page end address
  335. #endif
  336. #if SSD1306_LCDHEIGHT == 16
  337.         num_ack += ssd1306_i2c_send_command(inst, 1); // Page end address
  338. #endif
  339.         return num_ack;
  340. }

  341. int ssd1306_i2c_cls(ssd1306_i2c_ctrl_p inst)
  342. {
  343.         return ssd1306_i2c_fill(inst, 0, SSD1306_LCDWIDTH * SSD1306_LCDHEIGHT / 8);
  344. }

  345. #include"font8x8.h"

  346. int ssd1306_i2c_putchar(ssd1306_i2c_ctrl_p inst, const int ch)
  347. {
  348.         int v = ch - 1;
  349.         if(v >= 0x7F)v = 0;
  350.         return ssd1306_i2c_send_data(inst, &ascii8x8_vert[v * 8], 8);
  351. }

  352. void ssd1306_i2c_printf(ssd1306_i2c_ctrl_p inst, const char *format, ...)
  353. {
  354.         va_list ap;
  355.         char buf[4096];
  356.         int i;
  357.        
  358.         va_start(ap, format);
  359.        
  360.         vsnprintf(buf, sizeof buf, format, ap);
  361.        
  362.         for(i = 0; i < sizeof buf; i++)
  363.         {
  364.                 if(!buf[i])
  365.                         break;
  366.                 if(buf[i] >= 0x20)
  367.                         ssd1306_i2c_putchar(inst, buf[i]);
  368.         }
  369.        
  370.         va_end(ap);
  371. }

  372. #define I2C_GPIO_PIN 9, 8

  373. int main()
  374. {
  375.         wiringPiSetup();
  376.        
  377.         ssd1306_i2c_ctrl_t ssd1306;
  378.        
  379.         ssd1306_i2c_init(&ssd1306, I2C_GPIO_PIN, SSD1306_I2C_ADDRESS, ignore_nack);
  380.         ssd1306_i2c_boot(&ssd1306);
  381.         ssd1306_i2c_cls(&ssd1306);
  382.        
  383.         ssd1306_i2c_printf(&ssd1306, "Hello motherfucker ");
  384.        
  385.        
  386.         sleep(1);
  387.        
  388.         //printf("%d\n", ssd1306_i2c_send_command(&ssd1306, SSD1306_DISPLAYOFF));
  389.        
  390.         return 0;
  391. }
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 楼主| 发表于 2017-11-19 10:03:43 | 显示全部楼层
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  1. const unsigned char ascii8x8_vert[] =
  2. {
  3.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  4.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  5.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  6.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  7.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  8.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  9.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  10.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  11.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  12.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  13.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  14.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  15.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  16.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  17.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  18.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,

  19.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  20.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  21.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  22.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  23.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  24.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  25.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  26.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  27.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  28.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  29.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  30.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  31.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  32.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  33.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
  34.         0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, //  

  35.         0x00,0x00,0x00,0x00,0x2F,0x00,0x00,0x00, // !
  36.         0x00,0x00,0x03,0x00,0x03,0x00,0x00,0x00, // "
  37.         0x00,0x14,0x3E,0x14,0x3E,0x14,0x00,0x00, // #
  38.         0x00,0x00,0x24,0x2A,0x7F,0x2A,0x12,0x00, // $
  39.         0x02,0x05,0x15,0x0A,0x14,0x2A,0x28,0x10, // %
  40.         0x00,0x00,0x16,0x29,0x29,0x11,0x10,0x28, // &
  41.         0x00,0x00,0x00,0x00,0x03,0x00,0x00,0x00, // '
  42.         0x00,0x00,0x0C,0x12,0x21,0x00,0x00,0x00, // (
  43.         0x00,0x00,0x00,0x21,0x12,0x0C,0x00,0x00, // )
  44.         0x00,0x00,0x15,0x0E,0x1F,0x0E,0x15,0x00, // *
  45.         0x00,0x00,0x08,0x08,0x3E,0x08,0x08,0x00, // +
  46.         0x00,0x00,0x00,0x40,0x20,0x00,0x00,0x00, // ,
  47.         0x00,0x00,0x08,0x08,0x08,0x08,0x00,0x00, // -
  48.         0x00,0x00,0x00,0x00,0x20,0x00,0x00,0x00, // .
  49.         0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00, // /
  50.         0x00,0x0C,0x12,0x21,0x21,0x12,0x0C,0x00, // 0

  51.         0x00,0x00,0x00,0x22,0x3F,0x20,0x00,0x00, // 1
  52.         0x00,0x22,0x31,0x29,0x29,0x25,0x22,0x00, // 2
  53.         0x00,0x12,0x21,0x29,0x29,0x25,0x12,0x00, // 3
  54.         0x00,0x18,0x14,0x12,0x3F,0x10,0x00,0x00, // 4
  55.         0x00,0x17,0x25,0x25,0x25,0x25,0x19,0x00, // 5
  56.         0x00,0x1E,0x25,0x25,0x25,0x25,0x18,0x00, // 6
  57.         0x00,0x21,0x11,0x09,0x05,0x03,0x01,0x00, // 7
  58.         0x00,0x1A,0x25,0x25,0x25,0x25,0x1A,0x00, // 8
  59.         0x00,0x06,0x29,0x29,0x29,0x29,0x1E,0x00, // 9
  60.         0x00,0x00,0x00,0x00,0x24,0x00,0x00,0x00, // :
  61.         0x00,0x00,0x00,0x40,0x24,0x00,0x00,0x00, // ;
  62.         0x00,0x08,0x08,0x14,0x14,0x22,0x22,0x00, // <
  63.         0x00,0x14,0x14,0x14,0x14,0x14,0x14,0x00, // =
  64.         0x00,0x22,0x22,0x14,0x14,0x08,0x08,0x00, // >
  65.         0x00,0x02,0x01,0x29,0x09,0x06,0x00,0x00, // ?
  66.         0x18,0x24,0x42,0xBA,0xAA,0xBE,0x00,0x00, // @

  67.         0x00,0x30,0x0C,0x0B,0x0B,0x0C,0x30,0x00, // A
  68.         0x00,0x3F,0x25,0x25,0x25,0x1A,0x00,0x00, // B
  69.         0x0C,0x12,0x21,0x21,0x21,0x12,0x00,0x00, // C
  70.         0x00,0x3F,0x21,0x21,0x21,0x1E,0x00,0x00, // D
  71.         0x00,0x3F,0x25,0x25,0x25,0x21,0x00,0x00, // E
  72.         0x00,0x3F,0x05,0x05,0x05,0x01,0x00,0x00, // F
  73.         0x0C,0x12,0x21,0x29,0x29,0x1A,0x00,0x00, // G
  74.         0x00,0x3F,0x04,0x04,0x04,0x04,0x3F,0x00, // H
  75.         0x00,0x00,0x21,0x21,0x3F,0x21,0x21,0x00, // I
  76.         0x00,0x10,0x20,0x21,0x21,0x1F,0x00,0x00, // J
  77.         0x00,0x3F,0x08,0x0C,0x12,0x21,0x00,0x00, // K
  78.         0x00,0x3F,0x20,0x20,0x20,0x20,0x20,0x00, // L
  79.         0x00,0x3F,0x02,0x04,0x08,0x04,0x02,0x3F, // M
  80.         0x00,0x3F,0x02,0x04,0x08,0x10,0x3F,0x00, // N
  81.         0x00,0x00,0x1E,0x21,0x21,0x21,0x1E,0x00, // O
  82.         0x00,0x3F,0x05,0x05,0x05,0x02,0x00,0x00, // P

  83.         0x00,0x00,0x1E,0x21,0x21,0x21,0x5E,0x00, // Q
  84.         0x00,0x3F,0x05,0x0D,0x15,0x22,0x00,0x00, // R
  85.         0x00,0x00,0x12,0x25,0x29,0x29,0x12,0x00, // S
  86.         0x00,0x01,0x01,0x01,0x3F,0x01,0x01,0x01, // T
  87.         0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00, // U
  88.         0x01,0x06,0x18,0x20,0x20,0x18,0x06,0x01, // V
  89.         0x00,0x3F,0x10,0x08,0x04,0x08,0x10,0x3F, // W
  90.         0x00,0x21,0x12,0x0C,0x0C,0x12,0x21,0x00, // X
  91.         0x00,0x01,0x02,0x04,0x38,0x04,0x02,0x01, // Y
  92.         0x00,0x21,0x31,0x29,0x25,0x23,0x21,0x00, // Z
  93.         0x00,0x00,0x3F,0x21,0x21,0x00,0x00,0x00, // [
  94.         0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00, // \ bs
  95.         0x00,0x00,0x21,0x21,0x3F,0x00,0x00,0x00, // ]
  96.         0x00,0x00,0x02,0x01,0x02,0x00,0x00,0x00, // ^
  97.         0x00,0x20,0x20,0x20,0x20,0x20,0x20,0x00, // _
  98.         0x00,0x00,0x00,0x01,0x02,0x00,0x00,0x00, // `

  99.         0x00,0x10,0x2A,0x2A,0x2A,0x1A,0x3C,0x00, // a
  100.         0x00,0x3F,0x14,0x24,0x24,0x24,0x18,0x00, // b
  101.         0x00,0x00,0x18,0x24,0x24,0x24,0x00,0x00, // c
  102.         0x00,0x18,0x24,0x24,0x24,0x14,0x3F,0x00, // d
  103.         0x00,0x1C,0x2A,0x2A,0x2A,0x2A,0x0C,0x00, // e
  104.         0x00,0x00,0x08,0x3E,0x0A,0x00,0x00,0x00, // f
  105.         0x00,0x18,0xA4,0xA4,0x88,0x7C,0x00,0x00, // g
  106.         0x00,0x00,0x3F,0x04,0x04,0x38,0x00,0x00, // h
  107.         0x00,0x00,0x00,0x00,0x3D,0x00,0x00,0x00, // i
  108.         0x00,0x80,0x80,0x84,0x7D,0x00,0x00,0x00, // j
  109.         0x00,0x00,0x3F,0x10,0x28,0x24,0x00,0x00, // k
  110.         0x00,0x00,0x00,0x3F,0x20,0x00,0x00,0x00, // l
  111.         0x00,0x3C,0x04,0x08,0x08,0x04,0x3C,0x00, // m
  112.         0x00,0x00,0x3C,0x08,0x04,0x04,0x3C,0x00, // n
  113.         0x00,0x18,0x24,0x24,0x24,0x24,0x18,0x00, // o
  114.         0x00,0xFC,0x28,0x24,0x24,0x24,0x18,0x00, // p

  115.         0x00,0x18,0x24,0x24,0x24,0x28,0xFC,0x00, // q
  116.         0x00,0x00,0x3C,0x08,0x04,0x04,0x08,0x00, // r
  117.         0x00,0x00,0x24,0x2A,0x2A,0x12,0x00,0x00, // s
  118.         0x00,0x00,0x04,0x3E,0x24,0x04,0x00,0x00, // t
  119.         0x00,0x00,0x1C,0x20,0x20,0x10,0x3C,0x00, // u
  120.         0x00,0x0C,0x10,0x20,0x20,0x10,0x0C,0x00, // v
  121.         0x0C,0x30,0x20,0x10,0x10,0x20,0x30,0x0C, // w
  122.         0x00,0x24,0x28,0x10,0x10,0x28,0x24,0x00, // x
  123.         0x00,0x84,0x88,0x50,0x20,0x10,0x0C,0x00, // y
  124.         0x00,0x00,0x24,0x34,0x2C,0x24,0x00,0x00, // z
  125.         0x00,0x00,0x0C,0x3F,0x21,0x21,0x00,0x00, // {
  126.         0x00,0x00,0x00,0x00,0x7F,0x00,0x00,0x00, // |
  127.         0x00,0x00,0x21,0x21,0x3F,0x0C,0x00,0x00, // }
  128.         0x00,0x10,0x08,0x08,0x10,0x10,0x08,0x00, // ~
  129.         0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00, // 
  130.         0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, //
  131. };
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发表于 2017-11-19 19:31:31 | 显示全部楼层
与硬件同步交互在使用延迟时要尽量避免使用 yield 延迟,如果需要使用延迟首先选择“计数锁”
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 楼主| 发表于 2017-11-19 22:30:17 | 显示全部楼层
Ayala 发表于 2017-11-19 19:31
与硬件同步交互在使用延迟时要尽量避免使用 yield 延迟,如果需要使用延迟首先选择“计数锁” ...

主要是不想忙等待
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发表于 2017-12-12 20:29:47 | 显示全部楼层
0xAA55 发表于 2017-11-19 22:30
主要是不想忙等待

处理器和硬件交互 经常需要忙等 就算目标硬件控制器支持队列 也很多时候需要等待几tsc 或者等待几晶刻
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 楼主| 发表于 2020-3-25 18:34:20 | 显示全部楼层
我才不会说这是因为我不会配置香蕉派的WiringPi外设驱动,才强行写GPIO
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