【嵌入式】强行写GPIO实现I2C通讯，控制SSD1306显示屏显示图像
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。#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdarg.h>
#include<inttypes.h>
#include<wiringPi.h>
#include<unistd.h>
#define param_pins int scl_pin, int sda_pin
#define i2c_pin scl_pin, sda_pin
static void _i2c_delay()
{
// usleep(5);
// 不用延迟它也能实现效果
// 用了延迟反而变得贼慢
}
static void _i2c_start(param_pins)
{
pinMode(scl_pin, OUTPUT);
pinMode(sda_pin, OUTPUT);
// start condition
digitalWrite(scl_pin, HIGH);
_i2c_delay();
digitalWrite(sda_pin, HIGH);
_i2c_delay();
digitalWrite(sda_pin, LOW);
_i2c_delay();
digitalWrite(scl_pin, LOW);
_i2c_delay();
}
static void _i2c_stop(param_pins)
{
pinMode(scl_pin, OUTPUT);
pinMode(sda_pin, OUTPUT);
digitalWrite(scl_pin, LOW);
digitalWrite(sda_pin, HIGH);
_i2c_delay();
digitalWrite(scl_pin, HIGH);
_i2c_delay();
}
static void _i2c_send_bit(param_pins, const int value)
{
digitalWrite(sda_pin, value ? HIGH : LOW);
digitalWrite(scl_pin, HIGH);
_i2c_delay();
digitalWrite(scl_pin, LOW);
_i2c_delay();
}
static int _i2c_read_bit(param_pins)
{
int received;
digitalWrite(scl_pin, HIGH);
_i2c_delay();
received = digitalRead(sda_pin) == HIGH ? 1 : 0;
digitalWrite(scl_pin, LOW);
_i2c_delay();
return received;
}
static int _i2c_read_byte(param_pins)
{
int received = 0;
pinMode(scl_pin, OUTPUT);
pinMode(sda_pin, INPUT);
received |= _i2c_read_bit(i2c_pin) << 7;
received |= _i2c_read_bit(i2c_pin) << 6;
received |= _i2c_read_bit(i2c_pin) << 5;
received |= _i2c_read_bit(i2c_pin) << 4;
received |= _i2c_read_bit(i2c_pin) << 3;
received |= _i2c_read_bit(i2c_pin) << 2;
received |= _i2c_read_bit(i2c_pin) << 1;
received |= _i2c_read_bit(i2c_pin);
// send NACK
pinMode(sda_pin, OUTPUT);
_i2c_send_bit(i2c_pin, 1);
return received;
}
static void _i2c_write_byte(param_pins, const int value)
{
pinMode(scl_pin, OUTPUT);
pinMode(sda_pin, OUTPUT);
_i2c_send_bit(i2c_pin, value & 0x80 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x40 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x20 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x10 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x08 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x04 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x02 ? 1 : 0);
_i2c_send_bit(i2c_pin, value & 0x01 ? 1 : 0);
}
#define BLACK 0
#define WHITE 1
#define INVERSE 2
#define SSD1306_I2C_ADDRESS 0x3C// 011110+SA0+RW - 0x3C or 0x3D
// Address for 128x32 is 0x3C
// Address for 128x64 is 0x3D (default) or 0x3C (if SA0 is grounded)
/*=========================================================================
SSD1306 Displays
-----------------------------------------------------------------------
The driver is used in multiple displays (128x64, 128x32, etc.).
Select the appropriate display below to create an appropriately
sized framebuffer, etc.
SSD1306_128_64128x64 pixel display
SSD1306_128_32128x32 pixel display
SSD1306_96_16
-----------------------------------------------------------------------*/
#define SSD1306_128_64
// #define SSD1306_128_32
// #define SSD1306_96_16
/*=========================================================================*/
#if defined SSD1306_128_64 && defined SSD1306_128_32
#error "Only one SSD1306 display can be specified at once in SSD1306.h"
#endif
#if !defined SSD1306_128_64 && !defined SSD1306_128_32 && !defined SSD1306_96_16
#error "At least one SSD1306 display must be specified in SSD1306.h"
#endif
#if defined SSD1306_128_64
#define SSD1306_LCDWIDTH 128
#define SSD1306_LCDHEIGHT 64
#endif
#if defined SSD1306_128_32
#define SSD1306_LCDWIDTH 128
#define SSD1306_LCDHEIGHT 32
#endif
#if defined SSD1306_96_16
#define SSD1306_LCDWIDTH 96
#define SSD1306_LCDHEIGHT 16
#endif
#define SSD1306_SETCONTRAST 0x81
#define SSD1306_DISPLAYALLON_RESUME 0xA4
#define SSD1306_DISPLAYALLON 0xA5
#define SSD1306_NORMALDISPLAY 0xA6
#define SSD1306_INVERTDISPLAY 0xA7
#define SSD1306_DISPLAYOFF 0xAE
#define SSD1306_DISPLAYON 0xAF
#define SSD1306_SETDISPLAYOFFSET 0xD3
#define SSD1306_SETCOMPINS 0xDA
#define SSD1306_SETVCOMDETECT 0xDB
#define SSD1306_SETDISPLAYCLOCKDIV 0xD5
#define SSD1306_SETPRECHARGE 0xD9
#define SSD1306_SETMULTIPLEX 0xA8
#define SSD1306_SETLOWCOLUMN 0x00
#define SSD1306_SETHIGHCOLUMN 0x10
#define SSD1306_SETSTARTLINE 0x40
#define SSD1306_MEMORYMODE 0x20
#define SSD1306_COLUMNADDR 0x21
#define SSD1306_PAGEADDR 0x22
#define SSD1306_COMSCANINC 0xC0
#define SSD1306_COMSCANDEC 0xC8
#define SSD1306_SEGREMAP 0xA0
#define SSD1306_CHARGEPUMP 0x8D
#define SSD1306_EXTERNALVCC 0x1
#define SSD1306_SWITCHCAPVCC 0x2
// Scrolling #defines
#define SSD1306_ACTIVATE_SCROLL 0x2F
#define SSD1306_DEACTIVATE_SCROLL 0x2E
#define SSD1306_SET_VERTICAL_SCROLL_AREA 0xA3
#define SSD1306_RIGHT_HORIZONTAL_SCROLL 0x26
#define SSD1306_LEFT_HORIZONTAL_SCROLL 0x27
#define SSD1306_VERTICAL_AND_RIGHT_HORIZONTAL_SCROLL 0x29
#define SSD1306_VERTICAL_AND_LEFT_HORIZONTAL_SCROLL 0x2A
#define stop_if_nack 1
#define ignore_nack 0
typedef struct ssd1306_i2c_ctrl_struct
{
int sda_pin;
int scl_pin;
int chip_addr;
int check_ack;
}ssd1306_i2c_ctrl_t, *ssd1306_i2c_ctrl_p;
void ssd1306_i2c_init(ssd1306_i2c_ctrl_p inst, param_pins, const int chip_addr, const int check_ack)
{
memset(inst, 0, sizeof *inst);
inst->sda_pin = sda_pin;
inst->scl_pin = scl_pin;
inst->chip_addr = chip_addr;
inst->check_ack = check_ack;
}
int ssd1306_i2c_send_command(ssd1306_i2c_ctrl_p inst, const int command)
{
int num_ack = 0;
const int sda_pin = inst->sda_pin;
const int scl_pin = inst->scl_pin;
// start condition
_i2c_start(i2c_pin);
// address & R/W bit (write => 0)
_i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
// control bvte
_i2c_write_byte(i2c_pin, 0x00);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
// command
_i2c_write_byte(i2c_pin, command);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
// stop condition
_i2c_stop(i2c_pin);
return num_ack;
}
int ssd1306_i2c_send_data(ssd1306_i2c_ctrl_p inst, const void *data, const size_t cb_data)
{
int num_ack = 0;
const uint8_t *ptr = data;
size_t counter = cb_data;
const int sda_pin = inst->sda_pin;
const int scl_pin = inst->scl_pin;
// start condition
_i2c_start(i2c_pin);
// address & R/W bit (write => 0)
_i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
// control bvte
_i2c_write_byte(i2c_pin, 0x40);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
while(counter--)
{
// data
_i2c_write_byte(i2c_pin, *ptr++);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
}
// stop condition
_i2c_stop(i2c_pin);
return num_ack;
}
int ssd1306_i2c_fill(ssd1306_i2c_ctrl_p inst, const uint8_t val, const size_t cb_len)
{
int num_ack = 0;
size_t counter = cb_len;
const int sda_pin = inst->sda_pin;
const int scl_pin = inst->scl_pin;
// start condition
_i2c_start(i2c_pin);
// address & R/W bit (write => 0)
_i2c_write_byte(i2c_pin, (inst->chip_addr << 1));
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
// control bvte
_i2c_write_byte(i2c_pin, 0x40);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
while(counter--)
{
// data
_i2c_write_byte(i2c_pin, val);
// ACK
pinMode(sda_pin, INPUT);
if(_i2c_read_bit(i2c_pin)){if(inst->check_ack)return 0;}else num_ack ++;
}
// stop condition
_i2c_stop(i2c_pin);
return num_ack;
}
int ssd1306_i2c_boot(ssd1306_i2c_ctrl_p inst)
{
int num_ack = 0;
num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYOFF);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETDISPLAYCLOCKDIV);
num_ack += ssd1306_i2c_send_command(inst, 0xF0);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETMULTIPLEX);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_LCDHEIGHT - 1);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETDISPLAYOFFSET);
num_ack += ssd1306_i2c_send_command(inst, 0);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETSTARTLINE | 0);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_CHARGEPUMP);
num_ack += ssd1306_i2c_send_command(inst, 0x14);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_MEMORYMODE);
num_ack += ssd1306_i2c_send_command(inst, 0);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SEGREMAP | 0x1);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_COMSCANDEC);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETCOMPINS);
num_ack += ssd1306_i2c_send_command(inst, 0x12);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETCONTRAST);
num_ack += ssd1306_i2c_send_command(inst, 0xCF);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETPRECHARGE);
num_ack += ssd1306_i2c_send_command(inst, 0xF1);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_SETVCOMDETECT);
num_ack += ssd1306_i2c_send_command(inst, 0x40);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYALLON_RESUME);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_NORMALDISPLAY);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_DEACTIVATE_SCROLL);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_DISPLAYON);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_COLUMNADDR);
num_ack += ssd1306_i2c_send_command(inst, 0);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_LCDWIDTH - 1);
num_ack += ssd1306_i2c_send_command(inst, SSD1306_PAGEADDR);
num_ack += ssd1306_i2c_send_command(inst, 0); // Page start address (0 = reset)
#if SSD1306_LCDHEIGHT == 64
num_ack += ssd1306_i2c_send_command(inst, 7); // Page end address
#endif
#if SSD1306_LCDHEIGHT == 32
num_ack += ssd1306_i2c_send_command(inst, 3); // Page end address
#endif
#if SSD1306_LCDHEIGHT == 16
num_ack += ssd1306_i2c_send_command(inst, 1); // Page end address
#endif
return num_ack;
}
int ssd1306_i2c_cls(ssd1306_i2c_ctrl_p inst)
{
return ssd1306_i2c_fill(inst, 0, SSD1306_LCDWIDTH * SSD1306_LCDHEIGHT / 8);
}
#include"font8x8.h"
int ssd1306_i2c_putchar(ssd1306_i2c_ctrl_p inst, const int ch)
{
int v = ch - 1;
if(v >= 0x7F)v = 0;
return ssd1306_i2c_send_data(inst, &ascii8x8_vert, 8);
}
void ssd1306_i2c_printf(ssd1306_i2c_ctrl_p inst, const char *format, ...)
{
va_list ap;
char buf;
int i;
va_start(ap, format);
vsnprintf(buf, sizeof buf, format, ap);
for(i = 0; i < sizeof buf; i++)
{
if(!buf)
break;
if(buf >= 0x20)
ssd1306_i2c_putchar(inst, buf);
}
va_end(ap);
}
#define I2C_GPIO_PIN 9, 8
int main()
{
wiringPiSetup();
ssd1306_i2c_ctrl_t ssd1306;
ssd1306_i2c_init(&ssd1306, I2C_GPIO_PIN, SSD1306_I2C_ADDRESS, ignore_nack);
ssd1306_i2c_boot(&ssd1306);
ssd1306_i2c_cls(&ssd1306);
ssd1306_i2c_printf(&ssd1306, "Hello motherfucker ");
sleep(1);
//printf("%d\n", ssd1306_i2c_send_command(&ssd1306, SSD1306_DISPLAYOFF));
return 0;
} 点阵字体：const unsigned char ascii8x8_vert[] =
{
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, //
0x00,0x00,0x00,0x00,0x2F,0x00,0x00,0x00, // !
0x00,0x00,0x03,0x00,0x03,0x00,0x00,0x00, // "
0x00,0x14,0x3E,0x14,0x3E,0x14,0x00,0x00, // #
0x00,0x00,0x24,0x2A,0x7F,0x2A,0x12,0x00, // $
0x02,0x05,0x15,0x0A,0x14,0x2A,0x28,0x10, // %
0x00,0x00,0x16,0x29,0x29,0x11,0x10,0x28, // &
0x00,0x00,0x00,0x00,0x03,0x00,0x00,0x00, // '
0x00,0x00,0x0C,0x12,0x21,0x00,0x00,0x00, // (
0x00,0x00,0x00,0x21,0x12,0x0C,0x00,0x00, // )
0x00,0x00,0x15,0x0E,0x1F,0x0E,0x15,0x00, // *
0x00,0x00,0x08,0x08,0x3E,0x08,0x08,0x00, // +
0x00,0x00,0x00,0x40,0x20,0x00,0x00,0x00, // ,
0x00,0x00,0x08,0x08,0x08,0x08,0x00,0x00, // -
0x00,0x00,0x00,0x00,0x20,0x00,0x00,0x00, // .
0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00, // /
0x00,0x0C,0x12,0x21,0x21,0x12,0x0C,0x00, // 0
0x00,0x00,0x00,0x22,0x3F,0x20,0x00,0x00, // 1
0x00,0x22,0x31,0x29,0x29,0x25,0x22,0x00, // 2
0x00,0x12,0x21,0x29,0x29,0x25,0x12,0x00, // 3
0x00,0x18,0x14,0x12,0x3F,0x10,0x00,0x00, // 4
0x00,0x17,0x25,0x25,0x25,0x25,0x19,0x00, // 5
0x00,0x1E,0x25,0x25,0x25,0x25,0x18,0x00, // 6
0x00,0x21,0x11,0x09,0x05,0x03,0x01,0x00, // 7
0x00,0x1A,0x25,0x25,0x25,0x25,0x1A,0x00, // 8
0x00,0x06,0x29,0x29,0x29,0x29,0x1E,0x00, // 9
0x00,0x00,0x00,0x00,0x24,0x00,0x00,0x00, // :
0x00,0x00,0x00,0x40,0x24,0x00,0x00,0x00, // ;
0x00,0x08,0x08,0x14,0x14,0x22,0x22,0x00, // <
0x00,0x14,0x14,0x14,0x14,0x14,0x14,0x00, // =
0x00,0x22,0x22,0x14,0x14,0x08,0x08,0x00, // >
0x00,0x02,0x01,0x29,0x09,0x06,0x00,0x00, // ?
0x18,0x24,0x42,0xBA,0xAA,0xBE,0x00,0x00, // @
0x00,0x30,0x0C,0x0B,0x0B,0x0C,0x30,0x00, // A
0x00,0x3F,0x25,0x25,0x25,0x1A,0x00,0x00, // B
0x0C,0x12,0x21,0x21,0x21,0x12,0x00,0x00, // C
0x00,0x3F,0x21,0x21,0x21,0x1E,0x00,0x00, // D
0x00,0x3F,0x25,0x25,0x25,0x21,0x00,0x00, // E
0x00,0x3F,0x05,0x05,0x05,0x01,0x00,0x00, // F
0x0C,0x12,0x21,0x29,0x29,0x1A,0x00,0x00, // G
0x00,0x3F,0x04,0x04,0x04,0x04,0x3F,0x00, // H
0x00,0x00,0x21,0x21,0x3F,0x21,0x21,0x00, // I
0x00,0x10,0x20,0x21,0x21,0x1F,0x00,0x00, // J
0x00,0x3F,0x08,0x0C,0x12,0x21,0x00,0x00, // K
0x00,0x3F,0x20,0x20,0x20,0x20,0x20,0x00, // L
0x00,0x3F,0x02,0x04,0x08,0x04,0x02,0x3F, // M
0x00,0x3F,0x02,0x04,0x08,0x10,0x3F,0x00, // N
0x00,0x00,0x1E,0x21,0x21,0x21,0x1E,0x00, // O
0x00,0x3F,0x05,0x05,0x05,0x02,0x00,0x00, // P
0x00,0x00,0x1E,0x21,0x21,0x21,0x5E,0x00, // Q
0x00,0x3F,0x05,0x0D,0x15,0x22,0x00,0x00, // R
0x00,0x00,0x12,0x25,0x29,0x29,0x12,0x00, // S
0x00,0x01,0x01,0x01,0x3F,0x01,0x01,0x01, // T
0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00, // U
0x01,0x06,0x18,0x20,0x20,0x18,0x06,0x01, // V
0x00,0x3F,0x10,0x08,0x04,0x08,0x10,0x3F, // W
0x00,0x21,0x12,0x0C,0x0C,0x12,0x21,0x00, // X
0x00,0x01,0x02,0x04,0x38,0x04,0x02,0x01, // Y
0x00,0x21,0x31,0x29,0x25,0x23,0x21,0x00, // Z
0x00,0x00,0x3F,0x21,0x21,0x00,0x00,0x00, // [
0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00, // \ bs
0x00,0x00,0x21,0x21,0x3F,0x00,0x00,0x00, // ]
0x00,0x00,0x02,0x01,0x02,0x00,0x00,0x00, // ^
0x00,0x20,0x20,0x20,0x20,0x20,0x20,0x00, // _
0x00,0x00,0x00,0x01,0x02,0x00,0x00,0x00, // `
0x00,0x10,0x2A,0x2A,0x2A,0x1A,0x3C,0x00, // a
0x00,0x3F,0x14,0x24,0x24,0x24,0x18,0x00, // b
0x00,0x00,0x18,0x24,0x24,0x24,0x00,0x00, // c
0x00,0x18,0x24,0x24,0x24,0x14,0x3F,0x00, // d
0x00,0x1C,0x2A,0x2A,0x2A,0x2A,0x0C,0x00, // e
0x00,0x00,0x08,0x3E,0x0A,0x00,0x00,0x00, // f
0x00,0x18,0xA4,0xA4,0x88,0x7C,0x00,0x00, // g
0x00,0x00,0x3F,0x04,0x04,0x38,0x00,0x00, // h
0x00,0x00,0x00,0x00,0x3D,0x00,0x00,0x00, // i
0x00,0x80,0x80,0x84,0x7D,0x00,0x00,0x00, // j
0x00,0x00,0x3F,0x10,0x28,0x24,0x00,0x00, // k
0x00,0x00,0x00,0x3F,0x20,0x00,0x00,0x00, // l
0x00,0x3C,0x04,0x08,0x08,0x04,0x3C,0x00, // m
0x00,0x00,0x3C,0x08,0x04,0x04,0x3C,0x00, // n
0x00,0x18,0x24,0x24,0x24,0x24,0x18,0x00, // o
0x00,0xFC,0x28,0x24,0x24,0x24,0x18,0x00, // p
0x00,0x18,0x24,0x24,0x24,0x28,0xFC,0x00, // q
0x00,0x00,0x3C,0x08,0x04,0x04,0x08,0x00, // r
0x00,0x00,0x24,0x2A,0x2A,0x12,0x00,0x00, // s
0x00,0x00,0x04,0x3E,0x24,0x04,0x00,0x00, // t
0x00,0x00,0x1C,0x20,0x20,0x10,0x3C,0x00, // u
0x00,0x0C,0x10,0x20,0x20,0x10,0x0C,0x00, // v
0x0C,0x30,0x20,0x10,0x10,0x20,0x30,0x0C, // w
0x00,0x24,0x28,0x10,0x10,0x28,0x24,0x00, // x
0x00,0x84,0x88,0x50,0x20,0x10,0x0C,0x00, // y
0x00,0x00,0x24,0x34,0x2C,0x24,0x00,0x00, // z
0x00,0x00,0x0C,0x3F,0x21,0x21,0x00,0x00, // {
0x00,0x00,0x00,0x00,0x7F,0x00,0x00,0x00, // |
0x00,0x00,0x21,0x21,0x3F,0x0C,0x00,0x00, // }
0x00,0x10,0x08,0x08,0x10,0x10,0x08,0x00, // ~
0x00,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x00, //
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, //
}; 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” 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 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 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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