AVR ATmega16 Mini Development Board Interfaced with Temperature sensor
AVR mini development board has on board temperature sensor MCP9700. Here in this section, we discuss the interfacing of the same with its host controller ATmega16. ATmega16 has 8 channel 10-bit successive approximation ADC.
On the Mini Development Board the temperature sensor MCP9700 is connected to pin PA1 of the controller i.e, ADC1 via jumper J10. The MCP9700/9700A and MCP9701/9701A family of Linear Active Thermistor™ Integrated Circuit (IC) is an analog temperature sensor that converts temperature to analog voltage. It has an accuracy of ±2°C from 0°C to +70°C (MCP9700A/9701A) ±4°C from 0°C to +70°C (MCP9700/9701) while consuming 6µA (typical) of operating current. Sensitivity is 10mV/°C. At 0°C, the output is 500mV. So that’s the spec and description for MCP9700, now lets see its actual working here below.
Note: To use temperature sensor, don’t forget to short jumper J10. Leaving it open frees PA1 and it can be used for any other desired purpose.
Schematic
Sample code to check the temperature sensor is given below. The output is displayed on LCD.
Sample Code
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/************************************************************************************* HEADER FILES **************************************************************************************/ #define F_CPU 8000000UL #include<avr/io.h> #include<util/delay.h> /************************************************************************************* FUNCTION DECLARATION **************************************************************************************/ void Command(unsigned char cmd); void Data(unsigned char dat); volatile unsigned char a=0; int Adc_Converssion(unsigned char channel); void Int_Asci(int); /************************************************************************************* VARIABLE DECLARATION **************************************************************************************/ int Adc_Check=0,i=0; unsigned char temp[]="Temp:"; /************************************************************************************* MAIN FUNCTION **************************************************************************************/ int main() { DDRA = 0X00; /* set PA0 PIN as input */ DDRB = 0xFF; /* set LCD data lines as output */ DDRD = 0X62; /* (RS(PD5),RW(GND),EN(PD6)set as Output */ ADCSRA = 0X85; /* ADEN=1,ADPS2=1,ADPS1=0,ADPS0=0 */ _delay_us(15); /* Minimum Delay To Power On LCD To Rx Mode */ Command(0x30); /* LCD Specification Cmdmands */ _delay_us(5); Command(0x30); /* LCD Specification Cmdmands */ _delay_us(2); Command(0x30); /* LCD Specification Cmdmands */ Command(0x38); /* LCD Double Line Display Cmdmand */ Command(0x06); /* LCD Auto Increment Location Address Cmdmand */ Command(0x0C); /* LCD Display ON Cmdmand */ Command(0x01); /* LCD Display Clear Command */ _delay_us(1200); while(1) { Adc_Check = Adc_Converssion(0X41); /* reading sensor out from PA0 pin */ Adc_Check = ((Adc_Check*4.88)-500);/* calibration of votage corresponding temp: */ Adc_Check = (Adc_Check/10); /* 10mV=1 degree celcius */ Command(0X82); for(i=0;i<=4;i++) /* LCD display function */ { Data(temp[i]); } /* display function */ Command(0X88); Int_Asci(Adc_Check); /* display temparature */ Data(0xDF); /* notation for degre celcius */ Data('C'); /* notation for degre celcius */ } } /************************************************************************************* * Function : Adc_Conversion * * * * Description : Function to convert analogue value to digital * * * * * Parameters : channel - channel for ADC conversion * **************************************************************************************/ int Adc_Converssion(unsigned char channel) { volatile int b; volatile int ad=0; ADMUX=channel; /* channel selection */ ADCSRA=ADCSRA|0X40; /* ADSC=1,start conversion */ while((ADCSRA & 0x40) == 0x40); /* checking flag */ b = ADCL; /* reading LSB result */ ad = ADCH; /* reading MSB result */ ad = ad<<8; /* shift MSB 8 times */ ad = ad|b; /* combining MSB and LSB */ return ad; /* return adc reading */ } /************************************************************************************* * Function : Int_Asci * * * * Description : Function to convert integer value to ASCII * * * * Parameters : ab - integer to be converted * **************************************************************************************/ void Int_Asci(int ab) { char i; char array[4]; for(i=1;i<=2;i++) /* decimal to ascii conversion */ { array[i]=ab%10; /* spliting decimal value using '/'and '%' */ ab=ab/10; } for(i=2;i>=1;i--) { Data(array[i]+'0'); /* display in lcd */ } } /************************************************************************************* * Function : Command * * * * Description : Function to send a command to LCD * * * * Parameters : cmd - command to be sent * **************************************************************************************/ void Command(unsigned char cmd) { PORTD |= 0X40; /* contol line RS-0(cmd register), R/W-GND(write),E-1(enable) */ PORTB = cmd; /* command loaded to data port */ _delay_us(50); /* Minimun Delay For Hold On Data */ PORTD = 0X00; /* contol line RS-0(cmd register), R/W-GND(write),E-0(enable) */ } /************************************************************************************* * Function : Data * * * * Description : Function to display data on LCD * * * * Parameters : dat - data to be displayed * **************************************************************************************/ void Data(unsigned char dat) { PORTD |= 0X60; /* contol line RS-1(data register), R/W - GND(write), E-1(enable) */ PORTB = dat; /* data loaded to data port */ _delay_us(50); /* Minimun Delay For Hold On Data */ PORTD = 0X00; /* contol line RS-0(data register), R/W - GND(write), E-0(enable) */ } /************************************************************************************* END OF PROGRAM **************************************************************************************/ |
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