ATMega32 Interfaces To LM35 And 16x2 Character LCD

Overview

In some previous post, I have wrote some posts about analog to digital convert. This peripheral converts any analog output devices and converter them to digital value. Some analog output sensor like LM35 creates an analog voltage output linear to its 10 mV step temperature value.

A display device show the information or status of the MCU and other input output devices. I posted some examples on using the industrial standard HD44780 LCD controller.

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Example Program

In this example post, ATMega32 reads the analog temperature value and just display this information to the display. The temperature is in both degree Celsius and degree Fahrenheit.

Interfacing And Programming

LM35 connects to the analog input pin ADC7 - the user could select any analog pin within its 8 analog inputs. The MCU clocks at 16 MHz due to a pre-soldered crystal on the learning board. However, I set the ADC conversion clock rate to 1:128.

LM35DZ in TO-92 Package

The display operates in 4-bit interfacing mode. A single PORTD of the MCU is sufficient to do this task.

Schematic Diagram

C source code of this example lists below, click here to download a zip archive.

	/*
	* Lm35Lcd.c
	*
	* Created: 9/1/2020 9:20:11 AM
	* Author : aki-technical
	*/
	#include <avr/io.h>
	#include <stdio.h>
	#define F_CPU 16000000UL
	#include <util/delay.h>
	#define lcdPort PORTD
	#define lcdDir DDRD
	#define RS 0
	#define E 1
	void lcdPortInit(void){
	//Only PORTD Is LCD Port
	lcdDir=0xFF;
	}
	void writeCommand(char command){
	lcdPort=(command&0xF0)|(1<<E);
	lcdPort=(command&0xF0);
	_delay_us(50);
	lcdPort=(command<<4)|(1<<E);
	lcdPort=(command<<4);
	_delay_ms(3);
	}
	void writeChararacter(char character){
	lcdPort=(character&0xF0)|(1<<E)|(1<<RS);
	lcdPort=(character&0xF0)|(1<<RS);
	_delay_us(50);
	lcdPort=(character<<4)|(1<<E)|(1<<RS);
	lcdPort=(character<<4)|(1<<RS);
	_delay_ms(3);
	}
	void writeString(char *text){
	while(*text) writeChararacter(*text++);
	}
	/*This function ease of setting the cursor position*/
	void setXy(int x,int y){
	/*Select A 40x4 LCD*/
	char numberOfLines[4]={0x80,0xC0,0x94,0xD4};
	/* The position starts from (x,y)=(0,0) */
	writeCommand(numberOfLines[x]+y);
	}
	/*ADC Module Setting*/
	void adcInit(void){
	/*Select ADC7 To Read LM35*/
	DDRA&=~(1<<7);
	/*Turn On ADC Module ADC Clock Is 1:128*/
	ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);
	/*Select ADC7 For Analog Input*/
	ADMUX=0x07;
	}
	float readTemperature(void){
	float temperature;
	/*Begin The ADC Conversion*/
	ADCSRA|=(1<<ADSC);
	/*Wait For Completion*/
	while((ADCSRA&(1<<ADSC))==1);
	temperature=(ADCL+(ADCH<<8))*5.0/1024;
	/*Multiply by 100 to scale up the 1 C/10mV*/
	temperature*=100;
	/*Convert to integer temperature value*/
	return temperature;
	}
	void lcdInit(void){
	/*Initialize the LCD PORT*/
	lcdPortInit();
	/*Writing the instructions
	4-bit mode, 2-line,5x8 dot*/
	writeCommand(0b00110011);
	writeCommand(0b00110010);
	writeCommand(0b00101000);
	writeCommand(0x01);
	/*Turn On Display, Cursor Off*/
	writeCommand(0b00001100);
	/*Cursor Shift in Increment Mode*/
	writeCommand(0b00000110);
	}
	int main(void)
	{
	char temptxt[16];
	/*LCD degree character*/
	char degree=223;
	float temperature;
	float fahrenheit;
	lcdInit();
	adcInit();
	_delay_ms(350);
	while (1) {
	setXy(0,0);
	writeString("Temperature Read");
	setXy(1,0);
	temperature=readTemperature();
	fahrenheit=(temperature*1.8)+32;
	sprintf(temptxt,"%0.1f%cC %0.1f%cF ",temperature,degree,fahrenheit,degree);
	writeString(temptxt);
	}
	}

view raw Lm35Lcd.c hosted with ❤ by GitHub

Note: Without configuring the sprintf() function in the project property, it can't convert the float data type to string value. We must the project properties as follow.

1. Open the project properties by pressing ALT+F7. 

Tick the required tick box as shown in the picture

1. Fill the required link flag

Fill the text box with this string "-lprintf_flt"

Then we can use the sprintf() function with float data type properly. If you still have the problem with sprintf(), see this link because I got it work from there.