Diff: main.cpp

Revision:

0:a5f38f79c701

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun May 10 21:46:51 2015 +0000
@@ -0,0 +1,746 @@
+/**
+Project D-Weather Station
+Temperature measuring meter 
+@file main.cpp
+@brief headfile contain the functions prototypys,defines and global variable
+@author Sun Yizhi 
+@date May 2015
+*/
+#include "mbed.h"
+#include "BMP180.h"
+#include "N5110.h"
+
+/**
+@namespace lcd
+@brief initialize the lcd display
+@namespace leds
+@brief GPIO led for the green led
+@namespace button
+@brief use the ISR for the button
+*/
+
+
+// LCD control 
+N5110::N5110(PinName pwrPin, PinName scePin, PinName rstPin, PinName dcPin, PinName mosiPin, PinName sclkPin, PinName ledPin)
+{
+
+    spi = new SPI(mosiPin,NC,sclkPin); // create new SPI instance and initialise
+    initSPI();
+
+    // set up pins as required
+    led = new PwmOut(ledPin);
+    pwr = new DigitalOut(pwrPin);
+    sce = new DigitalOut(scePin);
+    rst = new DigitalOut(rstPin);
+    dc = new DigitalOut(dcPin);
+
+}
+
+// initialise function - powers up and sends the initialisation commands
+void N5110::init()
+{
+    turnOn();     // power up
+    wait_ms(10);  // small delay seems to prevent spurious pixels during mbed reset
+    reset();      // reset LCD - must be done within 100 ms
+
+    // function set - extended
+    sendCommand(0x20 | CMD_FS_ACTIVE_MODE | CMD_FS_HORIZONTAL_MODE | CMD_FS_EXTENDED_MODE);
+    // Don't completely understand these parameters - they seem to work as they are
+    // Consult the datasheet if you need to change them
+    sendCommand(CMD_VOP_7V38);    // operating voltage - these values are from Chris Yan's Library
+    sendCommand(CMD_TC_TEMP_2);   // temperature control
+    sendCommand(CMD_BI_MUX_48);   // bias
+
+    // function set - basic
+    sendCommand(0x20 | CMD_FS_ACTIVE_MODE | CMD_FS_HORIZONTAL_MODE | CMD_FS_BASIC_MODE);
+    normalMode();  // normal video mode by default
+    sendCommand(CMD_DC_NORMAL_MODE);  // black on white
+
+    // RAM is undefined at power-up so clear
+    clearRAM();
+
+}
+
+// sets normal video mode (black on white)
+void N5110::normalMode()
+{
+    sendCommand(CMD_DC_NORMAL_MODE);
+
+}
+
+// sets normal video mode (white on black)
+void N5110::inverseMode()
+{
+    sendCommand(CMD_DC_INVERT_VIDEO);
+}
+
+// function to power up the LCD and backlight
+void N5110::turnOn()
+{
+    // set brightness of LED - 0.0 to 1.0 - default is 50%
+    setBrightness(0.5);
+    pwr->write(1);  // apply power
+}
+
+// function to power down LCD
+void N5110::turnOff()
+{
+    setBrightness(0.0);  // turn backlight off
+    clearRAM();   // clear RAM to ensure specified current consumption
+    // send command to ensure we are in basic mode
+    sendCommand(0x20 | CMD_FS_ACTIVE_MODE | CMD_FS_HORIZONTAL_MODE | CMD_FS_BASIC_MODE);
+    // clear the display
+    sendCommand(CMD_DC_CLEAR_DISPLAY);
+    // enter the extended mode and power down
+    sendCommand(0x20 | CMD_FS_POWER_DOWN_MODE | CMD_FS_HORIZONTAL_MODE | CMD_FS_EXTENDED_MODE);
+    // small delay and then turn off the power pin
+    wait_ms(10);
+    pwr->write(0);
+
+}
+
+// function to change LED backlight brightness
+void N5110::setBrightness(float brightness)
+{
+    // check whether brightness is within range
+    if (brightness < 0.0)
+        brightness = 0.0;
+    if (brightness > 1.0)
+        brightness = 1.0;
+    // set PWM duty cycle
+    led->write(brightness);
+}
+
+
+// pulse the active low reset line
+void N5110::reset()
+{
+    rst->write(0);  // reset the LCD
+    rst->write(1);
+}
+
+// function to initialise SPI peripheral
+void N5110::initSPI()
+{
+    spi->format(8,1);    // 8 bits, Mode 1 - polarity 0, phase 1 - base value of clock is 0, data captured on falling edge/propagated on rising edge
+    spi->frequency(4000000);  // maximum of screen is 4 MHz
+}
+
+// send a command to the display
+void N5110::sendCommand(unsigned char command)
+{
+    dc->write(0);  // set DC low for command
+    sce->write(0); // set CE low to begin frame
+    spi->write(command);  // send command
+    dc->write(1);  // turn back to data by default
+    sce->write(1); // set CE high to end frame (expected for transmission of single byte)
+
+}
+
+// send data to the display at the current XY address
+// dc is set to 1 (i.e. data) after sending a command and so should
+// be the default mode.
+void N5110::sendData(unsigned char data)
+{
+    sce->write(0);   // set CE low to begin frame
+    spi->write(data);
+    sce->write(1);  // set CE high to end frame (expected for transmission of single byte)
+}
+
+// this function writes 0 to the 504 bytes to clear the RAM
+void N5110::clearRAM()
+{
+    int i;
+    sce->write(0);  //set CE low to begin frame
+    for(i = 0; i < WIDTH * HEIGHT; i++) { // 48 x 84 bits = 504 bytes
+        spi->write(0x00);  // send 0's
+    }
+    sce->write(1); // set CE high to end frame
+
+}
+
+// function to set the XY address in RAM for subsequenct data write
+void N5110::setXYAddress(int x, int y)
+{
+    if (x>=0 && x<WIDTH && y>=0 && y<HEIGHT) {  // check within range
+        sendCommand(0x80 | x);  // send addresses to display with relevant mask
+        sendCommand(0x40 | y);
+    }
+}
+
+// These functions are used to set, clear and get the value of pixels in the display
+// Pixels are addressed in the range of 0 to 47 (y) and 0 to 83 (x).  The refresh()
+// function must be called after set and clear in order to update the display
+void N5110::setPixel(int x, int y)
+{
+    if (x>=0 && x<WIDTH && y>=0 && y<HEIGHT) {  // check within range
+        // calculate bank and shift 1 to required position in the data byte
+        buffer[x][y/8] |= (1 << y%8);
+    }
+}
+
+void N5110::clearPixel(int x, int y)
+{
+    if (x>=0 && x<WIDTH && y>=0 && y<HEIGHT) {  // check within range
+        // calculate bank and shift 1 to required position (using bit clear)
+        buffer[x][y/8] &= ~(1 << y%8);
+    }
+}
+
+int N5110::getPixel(int x, int y)
+{
+    if (x>=0 && x<WIDTH && y>=0 && y<HEIGHT) {  // check within range
+        // return relevant bank and mask required bit
+        return (int) buffer[x][y/8] & (1 << y%8);
+    } else {
+        return 0;
+    }
+}
+
+// function to refresh the display
+void N5110::refresh()
+{
+    int i,j;
+
+    setXYAddress(0,0);  // important to set address back to 0,0 before refreshing display
+    // address auto increments after printing string, so buffer[0][0] will not coincide
+    // with top-left pixel after priting string
+
+    sce->write(0);  //set CE low to begin frame
+
+    for(j = 0; j < BANKS; j++) {  // be careful to use correct order (j,i) for horizontal addressing
+        for(i = 0; i < WIDTH; i++) {
+            spi->write(buffer[i][j]);  // send buffer
+        }
+    }
+    sce->write(1); // set CE high to end frame
+
+}
+
+// fills the buffer with random bytes.  Can be used to test the display.
+// The rand() function isn't seeded so it probably creates the same pattern everytime
+void N5110::randomiseBuffer()
+{
+    int i,j;
+    for(j = 0; j < BANKS; j++) {  // be careful to use correct order (j,i) for horizontal addressing
+        for(i = 0; i < WIDTH; i++) {
+            buffer[i][j] = rand()%256;  // generate random byte
+        }
+    }
+
+}
+
+// function to print 5x7 font
+void N5110::printChar(char c,int x,int y)
+{
+    if (y>=0 && y<6) {  // check if printing in range of y banks
+
+        for (int i = 0; i < 5 ; i++ ) {
+            int pixel_x = x+i;
+            if (pixel_x > 83)  // ensure pixel isn't outside the buffer size (0 - 83)
+                break;
+            buffer[pixel_x][y] = font5x7[(c - 32)*5 + i];
+            // array is offset by 32 relative to ASCII, each character is 5 pixels wide
+        }
+
+        refresh();  // this sends the buffer to the display and sets address (cursor) back to 0,0
+    }
+}
+
+// function to print string at specified position
+void N5110::printString(const char * str,int x,int y)
+{
+    if (y>=0 && y<6) {  // check if printing in range of y banks
+
+        int n = 0 ; // counter for number of characters in string
+        // loop through string and print character
+        while(*str) {
+
+            // writes the character bitmap data to the buffer, so that
+            // text and pixels can be displayed at the same time
+            for (int i = 0; i < 5 ; i++ ) {
+                int pixel_x = x+i+n*6;
+                if (pixel_x > 83) // ensure pixel isn't outside the buffer size (0 - 83)
+                    break;
+                buffer[pixel_x][y] = font5x7[(*str - 32)*5 + i];
+            }
+
+            str++;  // go to next character in string
+
+            n++;    // increment index
+
+        }
+
+        refresh();  // this sends the buffer to the display and sets address (cursor) back to 0,0
+    }
+}
+
+// function to clear the screen
+void N5110::clear()
+{
+    clearBuffer();  // clear the buffer then call the refresh function
+    refresh();
+}
+
+// function to clear the buffer
+void N5110::clearBuffer()
+{
+    int i,j;
+    for (i=0; i<WIDTH; i++) {  // loop through the banks and set the buffer to 0
+        for (j=0; j<BANKS; j++) {
+            buffer[i][j]=0;
+        }
+    }
+}
+
+// function to plot array on display
+void N5110::plotArray(float array[])
+{
+
+    int i;
+
+    for (i=0; i<WIDTH; i++) {  // loop through array
+        // elements are normalised from 0.0 to 1.0, so multiply
+        // by 47 to convert to pixel range, and subtract from 47
+        // since top-left is 0,0 in the display geometry
+        setPixel(i,47 - int(array[i]*47.0));
+    }
+
+    refresh();
+
+}
+
+// function to draw circle
+void N5110:: drawCircle(int x0,int y0,int radius,int fill)
+{
+    // from http://en.wikipedia.org/wiki/Midpoint_circle_algorithm
+    int x = radius;
+    int y = 0;
+    int radiusError = 1-x;
+
+    while(x >= y) {
+
+        // if transparent, just draw outline
+        if (fill == 0) {
+            setPixel( x + x0,  y + y0);
+            setPixel(-x + x0,  y + y0);
+            setPixel( y + x0,  x + y0);
+            setPixel(-y + x0,  x + y0);
+            setPixel(-y + x0, -x + y0);
+            setPixel( y + x0, -x + y0);
+            setPixel( x + x0, -y + y0);
+            setPixel(-x + x0, -y + y0);
+        } else {  // drawing filled circle, so draw lines between points at same y value
+
+            int type = (fill==1) ? 1:0;  // black or white fill
+
+            drawLine(x+x0,y+y0,-x+x0,y+y0,type);
+            drawLine(y+x0,x+y0,-y+x0,x+y0,type);
+            drawLine(y+x0,-x+y0,-y+x0,-x+y0,type);
+            drawLine(x+x0,-y+y0,-x+x0,-y+y0,type);
+        }
+
+
+        y++;
+        if (radiusError<0) {
+            radiusError += 2 * y + 1;
+        } else {
+            x--;
+            radiusError += 2 * (y - x) + 1;
+        }
+    }
+
+    refresh();
+}
+
+void N5110::drawLine(int x0,int y0,int x1,int y1,int type)
+{
+    int y_range = y1-y0;  // calc range of y and x
+    int x_range = x1-x0;
+    int start,stop,step;
+
+    // if dotted line, set step to 2, else step is 1
+    step = (type==2) ? 2:1;
+
+    // make sure we loop over the largest range to get the most pixels on the display
+    // for instance, if drawing a vertical line (x_range = 0), we need to loop down the y pixels
+    // or else we'll only end up with 1 pixel in the x column
+    if ( abs(x_range) > abs(y_range) ) {
+
+        // ensure we loop from smallest to largest or else for-loop won't run as expected
+        start = x1>x0 ? x0:x1;
+        stop =  x1>x0 ? x1:x0;
+
+        // loop between x pixels
+        for (int x = start; x<= stop ; x+=step) {
+            // do linear interpolation
+            int y = y0 + (y1-y0)*(x-x0)/(x1-x0);
+
+            if (type == 0)   // if 'white' line, turn off pixel
+                clearPixel(x,y);
+            else
+                setPixel(x,y);  // else if 'black' or 'dotted' turn on pixel
+        }
+    } else {
+
+        // ensure we loop from smallest to largest or else for-loop won't run as expected
+        start = y1>y0 ? y0:y1;
+        stop =  y1>y0 ? y1:y0;
+
+        for (int y = start; y<= stop ; y+=step) {
+            // do linear interpolation
+            int x = x0 + (x1-x0)*(y-y0)/(y1-y0);
+
+            if (type == 0)   // if 'white' line, turn off pixel
+                clearPixel(x,y);
+            else
+                setPixel(x,y);  // else if 'black' or 'dotted' turn on pixel
+
+        }
+    }
+
+    refresh();
+}
+
+void N5110::drawRect(int x0,int y0,int width,int height,int fill)
+{
+
+    if (fill == 0) { // transparent, just outline
+        drawLine(x0,y0,x0+width,y0,1);  // top
+        drawLine(x0,y0+height,x0+width,y0+height,1);  // bottom
+        drawLine(x0,y0,x0,y0+height,1);  // left
+        drawLine(x0+width,y0,x0+width,y0+height,1);  // right
+    } else { // filled rectangle
+        int type = (fill==1) ? 1:0;  // black or white fill
+        for (int y = y0; y<= y0+height; y++) {  // loop through rows of rectangle
+            drawLine(x0,y,x0+width,y,type);  // draw line across screen
+        }
+    }
+
+}
+// Sensor control 
+BMP180::BMP180(PinName sdaPin, PinName sclPin)
+{
+    i2c = new I2C(sdaPin,sclPin); // create new I2C instance and initialise
+    i2c->frequency(400000);       // I2C Fast Mode - 400kHz
+    leds = new BusOut(LED4,LED3,LED2,LED1);
+}
+
+Measurement BMP180::readValues()
+{
+    // algorithm for taking measurement is taken from datasheet
+    int32_t UT = readUncompensatedTemperatureValue();
+    int32_t UP = readUncompensatedPressureValue();
+    // once you have the uncompensated T and P, you can calculate the true T and P
+    // using the equations from the datasheet
+    int32_t T = calcTrueTemperature(UT);
+    int32_t P = calcTruePressure(UP);
+
+    Measurement measurement;
+    measurement.temperature = T*0.1;  // scaled by 0.1 C
+    measurement.pressure = P*0.01;    // Put pressure in mb
+
+    return measurement;
+}
+
+int32_t BMP180::readUncompensatedTemperatureValue()
+{
+    // from algorithm in datasheet - p15
+    sendByteToRegister(0x2E,0xF4);
+    wait_ms(5);  // 4.5 ms delay for OSS = 1
+    char MSB = readByteFromRegister(0xF6);
+    char LSB = readByteFromRegister(0xF7);
+    // combine in 16-bit value
+    int UT = (MSB << 8) | LSB;
+#ifdef DEBUG
+    UT = 27898;  // test data from datasheet
+    printf("****DEBUG MODE****\nUT = %d\n",UT);
+#endif
+    return UT;
+}
+
+int32_t BMP180::readUncompensatedPressureValue()
+{
+    // from datasheet
+    char byte = 0x34 + (oss << 6);
+    sendByteToRegister(byte,0xF4);
+    wait_ms(8);  // 7.5 ms delay for OSS = 1
+
+    char MSB = readByteFromRegister(0xF6);
+    char LSB = readByteFromRegister(0xF7);
+    char XLSB = readByteFromRegister(0xF7);
+    int UP = (MSB << 16 | LSB << 8 | XLSB) >> (8 - oss);
+
+#ifdef DEBUG
+    UP = 23843;   // test data from datasheet
+    printf("UP = %d\n",UP);
+#endif
+    return UP;
+}
+
+int32_t BMP180::calcTrueTemperature(int32_t UT)
+{
+    // equations from data sheet
+    X1 = ((UT - calibration.AC6)*calibration.AC5) >> 15;
+    X2 = (calibration.MC << 11) / (X1 + calibration.MD);
+    B5 = X1 + X2;
+    int32_t T = (B5 + 8) >> 4;
+#ifdef DEBUG
+    printf("****\nX1=%d\nX2=%d\nB5=%d\nT=%d\n",X1,X2,B5,T);
+#endif
+    return T;
+}
+
+int32_t BMP180::calcTruePressure(int32_t UP)
+{
+    // equations from data sheet
+    B6 = B5 - 4000;
+    X1 = (calibration.B2 * ((B6*B6) >> 12))>>11;
+    X2 = (calibration.AC2*B6)>>11;
+    X3 = X1 + X2;
+    B3 = (((calibration.AC1*4 + X3) << oss)+2)/4;
+#ifdef DEBUG
+    printf("*****\nB6=%d\nX1=%d\nX2=%d\nX3=%d\nB3=%d\n",B6,X1,X2,X3,B3);
+#endif
+    X1 = (calibration.AC3*B6)>>13;
+    X2 = (calibration.B1*((B6*B6)>>12))>>16;
+    X3 = ((X1+X2)+2)/4;
+    B4 = (calibration.AC4*(uint32_t)(X3+32768))>>15;
+#ifdef DEBUG
+    printf("X1=%d\nX2=%d\nX3=%d\nB4=%u\n",X1,X2,X3,B4);
+#endif
+    B7 = ((uint32_t)UP - B3)*(50000>>oss);
+#ifdef DEBUG
+    printf("B7=%u\n",B7);
+#endif
+    int32_t P;
+    if (B7 < 0x80000000)
+        P = (B7*2)/B4;
+    else
+        P = (B7/B4)*2;
+#ifdef DEBUG
+    printf("P=%d\n",P);
+#endif
+    X1 = (P>>8)*(P>>8);
+#ifdef DEBUG
+    printf("X1=%d\n",X1);
+#endif
+    X1 = (X1*3038)>>16;
+#ifdef DEBUG
+    printf("X1=%d\n",X1);
+#endif
+    X2 = (-7357*P)>>16;
+#ifdef DEBUG
+    printf("X2=%d\n",X2);
+#endif
+    P = P + (X1+X2+3791)/16;
+#ifdef DEBUG
+    printf("P=%d\n",P);
+#endif
+
+    return P;
+
+}
+
+// configure the barometer
+void BMP180::init()
+{
+    i2c->frequency(400000); // set Fast Mode I2C frequency
+
+    char data = readByteFromRegister(ID_REG);  // Section 4 - datasheet
+    if (data != 0x55) { // if correct ID not found, hang and flash error message
+        error();
+    }
+
+    readCalibrationData();
+
+    oss = 1;  // standard power oversampling setting
+
+#ifdef DEBUG
+    oss = 0;  // used when testing data sheet example
+#endif
+
+
+}
+
+// Reads factory calibrated data
+void BMP180::readCalibrationData()
+{
+
+    char eeprom[22];
+
+    readBytesFromRegister(EEPROM_REG_ADD,22,eeprom);
+    // store calibration data in structure
+    calibration.AC1 = (int16_t) (eeprom[0] << 8) | eeprom[1];
+    calibration.AC2 = (int16_t) (eeprom[2] << 8) | eeprom[3];
+    calibration.AC3 = (int16_t) (eeprom[4] << 8) | eeprom[5];
+    calibration.AC4 = (uint16_t) (eeprom[6] << 8) | eeprom[7];
+    calibration.AC5 = (uint16_t) (eeprom[8] << 8) | eeprom[9];
+    calibration.AC6 = (uint16_t) (eeprom[10] << 8) | eeprom[11];
+    calibration.B1 = (int16_t) (eeprom[12] << 8) | eeprom[13];
+    calibration.B2 = (int16_t) (eeprom[14] << 8) | eeprom[15];
+    calibration.MB = (int16_t) (eeprom[16] << 8) | eeprom[17];
+    calibration.MC = (int16_t) (eeprom[18] << 8) | eeprom[19];
+    calibration.MD = (int16_t) (eeprom[20] << 8) | eeprom[21];
+
+    // test data from data sheet
+#ifdef DEBUG
+    calibration.AC1 = 408;
+    calibration.AC2 = -72;
+    calibration.AC3 = -14383;
+    calibration.AC4 = 32741;
+    calibration.AC5 = 32757;
+    calibration.AC6 = 23153;
+    calibration.B1 = 6190;
+    calibration.B2 = 4;
+    calibration.MB = -32768;
+    calibration.MC = -8711;
+    calibration.MD = 2868;
+    printf("****EXAMPLE CALIBRATION DATA****\n");
+    printf("AC1=%d\nAC2=%d\nAC3=%d\nAC4=%u\nAC5=%u\nAC6=%u\nB1=%d\nB2=%d\nMB=%d\nMC=%d\nMD=%d\n",
+           calibration.AC1,calibration.AC2,calibration.AC3,calibration.AC4,calibration.AC5,calibration.AC6,
+           calibration.B1,calibration.B2,calibration.MB,calibration.MC,calibration.MD);
+#endif
+}
+
+
+// reads a byte from a specific register
+char BMP180::readByteFromRegister(char reg)
+{
+    int nack = i2c->write(BMP180_W_ADDRESS,&reg,1,true);  // send the register address to the slave
+    if (nack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    char rx;
+    nack = i2c->read(BMP180_W_ADDRESS,&rx,1);  // read a byte from the register and store in buffer
+    if (nack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    return rx;
+}
+
+// reads a series of bytes, starting from a specific register
+void BMP180::readBytesFromRegister(char reg,int numberOfBytes,char bytes[])
+{
+    int nack = i2c->write(BMP180_W_ADDRESS,&reg,1,true);  // send the slave write address and the configuration register address
+
+    if (nack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+    nack = i2c->read(BMP180_W_ADDRESS,bytes,numberOfBytes);  // read bytes
+    if (nack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+}
+
+// sends a byte to a specific register
+void BMP180::sendByteToRegister(char byte,char reg)
+{
+    char data[2];
+    data[0] = reg;
+    data[1] = byte;
+    // send the register address, followed by the data
+    int nack = i2c->write(BMP180_W_ADDRESS,data,2);
+    if (nack)
+        error();  // if we don't receive acknowledgement, flash error message
+
+}
+
+void BMP180::error()
+{
+    while(1) {
+        leds->write(15);
+        wait(0.1);
+        leds->write(0);
+        wait(0.1);
+    }
+}
+
+
+N5110 lcd(p7,p8,p9,p10,p11,p13,p26);//initialize the NOKIA 5110 lcd screen
+BMP180 bmp(p28,p27);//initialize the specific temperature sensor
+BusOut leds(LED4,LED3,LED2,LED1);//initialize the leds of the mbed
+DigitalOut led(p24);//initialize the green led on the printed circuit board
+InterruptIn button(p18);//initialize the button on the printed circuit board
+
+#define up 1  // define up is 1 
+#define down 0  // define down is 0
+
+int state = up;//initialize state to up
+
+int buttonFlag = 0;//initialize buttonFlag to down
+
+/** 
+@Interrupt Service Routine
+*/
+void buttonPressed()
+{
+    state = !state;//when button is pressed state will be changed
+}    
+
+
+int main()
+{       
+        lcd.init();//initialize the display screen
+        bmp.init();//initialize the temperature sensor
+        lcd.printString("Temperature",2,2);//the opening word is temperature
+        wait(3.0);//after three seconds start to measuring temperature
+        Measurement measurement;//Measurement is a function and measurement is a variable
+        button.rise(&buttonPressed);//event generated on rising edge
+        led = 1;//set the green led on when turn on the deivce
+     while(1)
+        {
+             
+            measurement = bmp.readValues();//initialize the value of variable measurement from the function bmp.readValues()
+            
+            char t[14];//create a buffer 't' to store 14 characters
+            int length = sprintf(t,"T = %.2f C",measurement.temperature);//print formatted data to buffer 't'
+        // it is important the format specifier ensures the length will fit in the buffer
+            
+            float k = measurement.temperature + 273;//a transform function make the unit from Centigrade to Kelvin
+            char kel[14];//create a buffer 'kel' to store 14 characters
+            length = sprintf(kel,"T = %.2f K",k);//print formatted data to buffer 'kel'
+        // it is important the format specifier ensures the length will fit in the buffer 
+             
+            char p[14];//create a buffer 'p' to store 14 characters
+            length = sprintf(p,"P = %.2f mb",measurement.pressure);//print formatted data to buffer'p'
+        // it is important the format specifier ensures the length will fit in the buffer
+           
+            wait(0.5);//after one second to do next measurement
+            lcd.clear();//clear the buffer
+            
+        
+            switch(state)
+                {
+                    case up:// at up case
+                        state = 1;//let state to 1
+                        lcd.printString(t,0,1);//display the temperature in centigrade on the lcd screen 
+                        lcd.printString(p,0,3);//display the atmospheric pressure on the lcd screen    
+                        break;//out of the function
+                    case down://at down case
+                        state = 0;//let state to 0
+                        lcd.printString(kel,0,1);//display the temperature in kelvin on the lcd screen 
+                        lcd.printString(p,0,3);//display the atmospheric pressure on the lcd screen   
+                        break;//out of the function
+                    default:
+                        break;   
+                }
+             
+            if(measurement.temperature > 25.00)//when the value of variable temperature is bigger than 25
+                {
+                    led =1;//led will be on state 
+                    wait(0.1);//led will blink in each 0.1 second
+                    led =0;//led will be down state
+                    wait(0.1);//led will blink in each 0.1 second
+                }
+            
+        }
+}
+    
+
+
+
+
+
+
+