看大神如何自制一个GPS速度计

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• 1. Arduino Uno开发板（其他版本的Arduino开发板也可以使用）。
• 2.GPS模块，购买地址：https://www.dfrobot.com/wiki/index.php?title=GPS_M...
• 3.液晶显示屏，购买地址：http://www.aliexpress.com/item/20PIN-LCD12864-Graphic-LCD-Module-KS0107-KS0108-Drive-IC-5V-Yellow-Backlight/2037961119.html?spm=2114.01020208.3.40.olQVGl&ws_ab_test=searchweb201556_7_79_78_77_80,searchweb201644_5,searchweb201560_9
• 4.一个10K的微调电位，用来调整LCD的对比度。
• 5.4.7k的电位计，用来调整LCD的亮度。
• 6.100欧姆的电阻器，用来限制通过LCD的电流。
• 7.线材，吸盘，自粘魔术贴，厨房铝箔或类似的东西，烙铁，钳子和热熔胶枪等等。
• 可选配件：
• 8.可为Arduino开发板和LCD等设备供电的USB线。
• 9.两个5V的USB车载电源适配器，电流输出至少要达到1A。
• 10.塑料外壳（你也可以自己做一个）。
• 11.当然，首先你得有辆车。
  
  

-在10k微调电位的布线上，我做了一些调整。

-我将另一个4.7k的电位计和100欧姆的电阻器串联了起来，这样就可以控制LCD的亮度了。

• OpenGLCD，下载链接：https://code.google.com/p/glcd-arduino/downloads/list
  
  

更多详细信息请参阅：http://playground.arduino.cc/Code/GLCDks0108和https://bitbucket.org/bperrybap/openglcd/wiki/Home。

• tinyGPS，下载地址：http://arduiniana.org/libraries/tinygps/
  
  

解压下载好的文件并将它们放入你的Arduino库文件夹中（一般为C:Program Files (x86)Arduinolibraries）。如果Arduino IDE处于开机状态，请关掉并重启，这样才能加载出新的库。

C:Program Files (x86)ArduinolibrariesopenGLCDbitmapsutilsglcdMakeBitmap

#include //math library to use for round function

#include "TinyGPS.h" //GPS module library

#include // LCD library

TinyGPS gps; //create a gps object

float fLat, fLong; //floats for longitude and latitude; will be used to determine whether the GPS data is up to date or not

unsigned long fix_age; // returns +- latitude/longitude in degrees

int digit1, digit2, digit3; //integers to hold the three digits making up the speed

int iSpeed; //integer to hold the speed value from the GPS module

void setup()

{

Serial.begin(9600); //start the serial communication

// initialise the library, non inverted writes pixels onto a clear screen

GLCD.Init(NON_INVERTED);

}

void loop()

{

while (Serial.available())

{

//incoming serial data from GPS

int c = Serial.read();

if (gps.encode(c))

{

// process new gps info here, in case you want to display more details

}

}

gps.f_get_position(&fLat, &fLong, &fix_age); //get longitude and latitude, used to find if data is up to date

if (fix_age == TinyGPS::GPS_INVALID_AGE || fix_age > 2000)

{

//data was not updated for some time, assume that GPS connection is lost

iSpeed = 0;

}

else

{

//GPS connection is up to date, get the speed information, and round it to closest integer value

iSpeed = round(gps.f_speed_kmph()); // speed in km/h

}

//when not moving, the GPS module will still read some "speed" value, not necessarily zero

//in that case assume the car is not moving; only display values greater than 2

if (iSpeed == 1) iSpeed = 0;

displaySpeed(iSpeed); //call function to display the speed, digit by digit

}

void displaySpeed(int iSpeed)

{

//"simple" maths to extract each digit value

digit1 = iSpeed / 100;

iSpeed = iSpeed - (digit1 * 100);

digit2 = iSpeed / 10;

digit3 = iSpeed - (digit2 *10);

//display "blank" bitmap when necessary, instead of number zero

if (digit2 == 0 && digit1 == 0) digit2 = -1; //digit 2 is blank

if (digit1 == 0) digit1 = -1; //digit 1 is blank

//call function to display each digit, at their required position

drawDigit(digit1, 0);

drawDigit(digit2, 45);

drawDigit(digit3, 90);

}

void drawDigit(int digit, int pos)

{

switch (digit)

{

case 0:

GLCD.DrawBitmap(Number0, pos, 0);

break;

case 1:

GLCD.DrawBitmap(Number1, pos, 0);

break;

case 2:

GLCD.DrawBitmap(Number2, pos, 0);

break;

case 3:

GLCD.DrawBitmap(Number3, pos, 0);

break;

case 4:

GLCD.DrawBitmap(Number4, pos, 0);

break;

case 5:

GLCD.DrawBitmap(Number5, pos, 0);

break;

case 6:

GLCD.DrawBitmap(Number6, pos, 0);

break;

case 7:

GLCD.DrawBitmap(Number7, pos, 0);

break;

case 8:

GLCD.DrawBitmap(Number8, pos, 0);

break;

case 9:

GLCD.DrawBitmap(Number9, pos, 0);

break;

default:

GLCD.DrawBitmap(NumberBlank, pos, 0);

break;

}

}

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