嵌入式

嵌入式实验7——字符设备驱动程序

2019-07-12 18:57发布

站内文章 / 嵌入式Linux
14776 0 977
实验七——字符设备驱动程序
日期：2016-6-10
一、实验目的 1. 学习嵌入式Linux的GPIO的使用方式； 2. 学习嵌入式Linux的Arduino接口库； 3. 学习使用面包板搭简单的外部电路； 4. 学习Linux设备驱动程序的开发过程。 5. 学习在内核中访问外设寄存器，操纵外设的方法。 二、实验器材 硬件 Ÿ  Linux实验板卡一块； Ÿ  5V/1A电源一个； Ÿ  microUSB线一根； Ÿ  MAX7219驱动的8x8 LED矩阵一个； Ÿ  面包板一块； Ÿ  PC（Windows/Linux）一台； Ÿ  USB-TTL串口线一根； 软件 Ÿ  交叉编译软件； Ÿ  Fritzing。 三、实验步骤 1. 设计方案，画连线示意图； Vcc-1，Clk-2，Cs-3，Din-4，Gnd-5 2. 在面包板上连线，完成外部电路； 3. 编写C/C++程序，采用Arduino-ish库或虚拟文件系统访问GPIO，实现在矩阵上显示文字或图案； 使用WiringPi库访问GPIO，在矩阵上显示图案“ZJ” #define DIN 4 #define CS 3 #define CLK 2 #include #include #include #include void write_byte(unsigned charb){ unsigned char i, tmp; for (i=0; i<8; i++){ tmp = (b & 0x80) > 0; b <<= 1; if(tmp==1){ digitalWrite(DIN,HIGH); } else{ digitalWrite(DIN,LOW); } digitalWrite(CLK, HIGH); digitalWrite(CLK, LOW); } } void write_word(unsigned charaddr, unsigned char num){ digitalWrite(CS, HIGH); digitalWrite(CS, LOW); digitalWrite(CLK, LOW); write_byte(addr); write_byte(num); digitalWrite(CS, HIGH); } void Matrix_init(){ write_word(0x09, 0x00); write_word(0x0a, 0x03); write_word(0x0b, 0x07); write_word(0x0c, 0x01); } void Matrix_render(unsignedchar* tmp){ int i; for (i=0; i<8; i++){ printf("%d %d ", i, tmp[i]); write_word(i+1, tmp[i]); } } void Matrix_clear(){ unsigned char ZJ[]={ 0xF8, 0x10, 0x2F, 0x41, 0xF9, 0x01, 0x09,0x06 }; Matrix_render(ZJ); } int main(){ wiringPiSetup(); pinMode(DIN,OUTPUT); pinMode(CS,OUTPUT); pinMode(CLK,OUTPUT); Matrix_init(); Matrix_clear(); return 0; }

4. 编写字符设备驱动程序，直接访问GPIO控制寄存器，能将write()送来的单个字符在矩阵上显示出来 内核模块编写： #include #include #include #include #include #include #include #include #include #include #define DIN 4 #define CS 3 #define CLK 2 void write_byte(unsigned charb){ unsigned char i, tmp; for (i=0; i<8; i++){ tmp = (b & 0x80) > 0; b <<= 1; gpio_set_value(DIN, tmp); gpio_set_value(CLK, 1); gpio_set_value(CLK, 0); } } void write_word(unsigned charaddr, unsigned char num){ gpio_set_value(CLK, 0); gpio_set_value(CS, 1); gpio_set_value(CS, 0); write_byte(addr); write_byte(num); gpio_set_value(CS, 1); } void Matrix_render(unsignedchar* tmp){ int i; for (i=0; i<8; i++){ write_word(i+1, tmp[i]); } } unsigned char digits[][8]={ {0x1c, 0x22, 0x22, 0x22, 0x22, 0x22, 0x22,0x1c}, // 0 {0x08, 0x18, 0x08, 0x08, 0x08, 0x08, 0x08,0x1c}, // 1 {0x1c, 0x22, 0x22, 0x04, 0x08, 0x10, 0x20, 0x3e},// 2 {0x1c, 0x22, 0x02, 0x0c, 0x02, 0x02, 0x22,0x1c}, // 3 {0x04, 0x0c, 0x14, 0x14, 0x24, 0x1e, 0x04,0x04}, // 4 {0x3e, 0x20, 0x20, 0x3c, 0x02, 0x02, 0x22,0x1c}, // 5 {0x1c, 0x22, 0x20, 0x3c, 0x22, 0x22, 0x22,0x1c}, // 6 {0x3e, 0x24, 0x04, 0x08, 0x08, 0x08, 0x08,0x08}, // 7 {0x1c, 0x22, 0x22, 0x1c, 0x22, 0x22, 0x22,0x1c}, // 8 {0x1c, 0x22, 0x22, 0x22, 0x1e, 0x02, 0x22,0x1c}, // 9 }; unsigned char ZJ[]={ 0xF8,0x10, 0x2F, 0x41, 0xF9, 0x01, 0x09, 0x06 }; void Matrix_clear(void){ Matrix_render(ZJ); } void Matrix_init(void){ write_word(0x09, 0x00); write_word(0x0a, 0x03); write_word(0x0b, 0x07); write_word(0x0c, 0x01); Matrix_clear(); } #define BUFFERSIZE 128 #define DELAYTIME 1 unsigned char disp[BUFFERSIZE]; int head = 0, tail = 0; static struct timer_list timer; void Matrix_next_display(unsignedlong); void ptr_inc(int *ptr){ *ptr = (*ptr + 1) % BUFFERSIZE; } static voidtimer_register(struct timer_list* ptimer){ init_timer(ptimer); ptimer->data = DELAYTIME; ptimer->expires = jiffies + (DELAYTIME *HZ); ptimer->function = Matrix_next_display; add_timer(ptimer); } void disp_start(void){ timer_register(&timer); } voidMatrix_next_display(unsigned long data){ if (head != tail){ unsigned char *ptr = LM; unsigned char c = disp[head]; if ('0' <= c && c <='9'){ ptr = digits[c - '0']; } Matrix_render(ptr); ptr_inc(&head); disp_start(); }else{ Matrix_clear(); } } static int matrix_write(structfile *file, const char __user *buffer, size_t count, loff_t *ppos){ int i; if (head == tail && count > 0){ disp_start(); } for (i=0; i

编译内核模块，载入，运行。该模块在加载到系统内部时，会申请在/dev目录下生成一个matrix文件。使用的时候直接向其输出想要在点阵上显示的字符即可。 pi@raspberrypi ~ $make pi@raspberrypi ~ $ sudo insmod matrix.ko pi@raspberrypi ~ $ cd /dev pi@raspberrypi /dev $ sudochown pi:pi matrix pi@raspberrypi /dev $ echo0123456789 > matrix

5. GPIO库的来源 -> 安装了Wiringpi库  

热门文章