Lluis Nadal / Mbed 2 deprecated MCP9800_Test

Test for MCP9800. 9-12 bit temperature sensor and thermostat with I2C (two-wire) SMBus compatible interface.

Dependencies:   mbed

main.cpp@2:2838bca55216, 2011-08-10 (annotated)

Committer:
lnadal
Date:
Wed Aug 10 06:52:29 2011 +0000
Revision:
2:2838bca55216
Parent:
1:5dbac5939fd7 

        

        
Who changed what in which revision?

        

            
                
UserRevisionLine numberNew contents of line

            
            


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#include "mbed.h"





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/*





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***************************************************************************





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MCP9800_Test. 9-12 bit temperature sensor and thermostat.





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2.7-5.5 V. 4.7kOhm pull-up resistors at SDA and SCLK.





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This program sets 12 bit ambient temperature readings resolution.





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Pointer bits:





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00: temperature register. 01: configuration register.





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10: temperature hysteresis register. 11: temperature limit-set register.





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Author: Lluis Nadal. August 2011.





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***************************************************************************





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*/





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I2C i2c(p9, p10); // SDA, SCL





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Serial pc(USBTX, USBRX);





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const int addr_R = 0x91; // Address to read





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const int addr_W = 0x90; // Address to write





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//const int addr_R = 0x9B ; // Address to read





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//const int addr_W = 0x9A; // Address to write





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char data[3];





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char TL[2];





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char TLR[2];





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char TH[2];





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char CR[1];





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int t;





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float temp;





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void read_temp() {





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    int sign;





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x00);// Write pointer to ambient temperature register





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    i2c.read(addr_R, data, 2);





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    i2c.stop();





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    //pc.printf("Temperature register: (%d, %d)\r\n",data[0], data[1]);





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    sign = data[0]>>7;





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    //pc.printf("Sign: %d \r\n",sign);





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    if (sign == 1) { // If number is negative





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        data[0] = ~data[0]; // Inverts (compliments)the bits





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        data[1] = ~data[1]; // Inverts (compliments)the bits





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        t = data[0];





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        t = -((t<<4) | (data[1]>>4)+1);// Packs and adds one to convert to negative integer





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        temp = t/16.0;





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    }





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    else {





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        t = data[0];





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        t = ((t<<4) | (data[1]>>4));





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        temp = t/16.0;





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    }





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    pc.printf("Temperature: %.4f C\r\n",temp);





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    pc.printf("\r\n");





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}





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void read_TL() {      // Read temperature limit register





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x03);// Write pointer to TL register





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    i2c.read(addr_R, TLR, 2);





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    i2c.stop();





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    pc.printf("Temperature limit register: (%d, %d)\r\n",TLR[0], TLR[1]);





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    pc.printf("\r\n");





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}





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void read_TH() {     // Read hysteresis register





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x02);// Write pointer to TH register





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    i2c.read(addr_R, TH, 2);





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    i2c.stop();





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    pc.printf("Temperature hysteresis register: (%d, %d)\r\n",TH[0], TH[1]);





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    pc.printf("\r\n");





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}





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void read_CR() {        // Read configuration register





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x01);// Write pointer to configuration register





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    i2c.read(addr_R, CR, 1);





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    i2c.stop();





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    pc.printf("Configuration register: (%d)\r\n",CR[0]);





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    pc.printf("\r\n");





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}





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// Set temperature limit (9-bit)





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void set_TL(float n) {  // -25.4375, 25.4375, 125, -55...





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    char msb;





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    char lsb;





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    if (n < 0) {





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        t = (int)(-n*16.0-1);





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        pc.printf("t = %d\r\n", t);





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        t = t<<4;





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        lsb = t & 0xFF;





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        msb = t>>8;





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        lsb = ~lsb; //Inverts (compliments)the bits





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        msb = ~msb; //Inverts (compliments)the bits





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//pc.printf("(%d, %d)\r\b", msb, lsb);





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    } else {





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        t = (int)(n*16.0);





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        t = t<<4;





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        lsb = t & 0xFF;





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        msb = t>>8;





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//pc.printf("(%d, %d)\r\b", msb, lsb);





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    }





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x03);// Write pointer to temperature-limit register





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    i2c.write(msb);// Write data





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    i2c.write(lsb);// Write data





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    i2c.stop();





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}





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// Set hysteresis register (9-bit)





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void set_TH(float n) {  // -25.4375, 25.4375, 125, -55...





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    char msb;





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    char lsb;





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    if (n < 0) {





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        t = (int)(-n*16.0-1);





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        pc.printf("t = %d\r\n", t);





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        t = t<<4;





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        lsb = t & 0xFF;





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        msb = t>>8;





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        lsb = ~lsb; //Inverts (compliments)the bits





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        msb = ~msb; //Inverts (compliments)the bits





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//pc.printf("(%d, %d)\r\b", msb, lsb);





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    } else {





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        t = (int)(n*16.0);





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        t = t<<4;





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        lsb = t & 0xFF;





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        msb = t>>8;





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//pc.printf("(%d, %d)\r\b", msb, lsb);





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    }





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x02);// Write pointer to hysteresis register





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    i2c.write(msb);// Write data





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    i2c.write(lsb);// Write data





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    i2c.stop();





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}





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int main() {





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    i2c.frequency(200000); // Max 400000 Hz





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    pc.printf("Initial readings: \r\n");





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    pc.printf("\r\n");





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    read_TL(); // Read temperature limit register





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    read_TH(); // Read hysteresis register





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    read_CR(); // Read configuration register





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    // Set 12 bit resolution





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    i2c.start();





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    i2c.write(addr_W);//Address to write pointer





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    i2c.write(0x01);// Write pointer to configuration register





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    i2c.write(0x60);// Write data





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    i2c.stop();





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    // Set temperature limit (9-bit)





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    set_TL(25.4375);   // -25.4375, 25.4375, 125, -55...





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// If ambient temperature > temperature limit then alert pin is low (with a pull-up resistor).





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    // Set hysteresis register (9-bit)





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    set_TH(24.4375);   // -25.4375, 25.4375, 125, -55...





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    wait(1);





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    pc.printf("\r\n");





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    pc.printf("Readings after changes: \r\n");





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    pc.printf("\r\n");





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    read_TL();       // Read temperature limit register





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    read_TH();       // Read hysteresis register





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    read_CR();       // Read configuration register





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    read_temp();     // Read ambient temperature





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    pc.printf("\r\n");





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}