MSP-EXP430F5529 & CCS: Temperature sensor using LM35 and LCD102x64

MrChunckuee mayo 04, 2018

Circuit:
The connection is very basic, the sensor to VCC and GND, the signal Vout of the LM35 is connected to the analog channel A6 of the MSP.


Code:
To obtain the temperature we need to perform a few calculations, for example in the LM35 datasheet it tells us that Vout = 10mV / ° C, in other words 1 ° C = 10mV, for example if we have a temperature of 30 ° C we will have Vout = 300mV, another point that we should consider will be the resolution of the ADC, in this case it is 12 bits, this means that we can have values ​​from 0 to 4096, to know what voltage corresponds to a bit we can say that; 1Bit = 3.3V / 4096 = 3300mV / 4096 = 0.8056mV.

With this we can know how many bits will be present in A0 when the temperature is 30 ° C, therefore Bits30 ° C = 300mV / 0.8056mV = 372.39.

The ways of presenting the equation that describes the behavior of the temperature can be of different forms but in the end the same result is achieved, I do it in the following way, of course, considering the previous calculations.

1 Bit = 0.8056mV
1 ° C = 10mV

And applying a rule of three we have 1 Bit = 0.8056mV * ° C / 10mV = 0.08056 ° C

Then I can deduce that if this constant is multiplied by the bits in A0, I will obtain my desired temperature, for example; 0.08056 * 373.30 = 29.99 ° C, considering that we have not used all the decimals we can say that our temperature is correct.

With this constant we reduce a little the process in the code, to avoid making the divisions, I must also mention that in the code I take 32 samples (1 sample every 32mS approximately) and then I get the average value with a displacement, so I update the temperature in approximately 1 second and show it on the screen, there is also a bar where we show from 10 ° C to 45 ° C, when the temperature is less at 45 ° C the LED1 changes state every second, when it is higher the LED1 changes its status every 32 milliseconds (flashing faster).
/*******************************************************************************
*
* MSP-EXP430F5529_008: Temperature sensor using LM35
*
*******************************************************************************
* FileName: main.c
* Processor: MSP430F5529
* Complier: CCS 7.2.0.00013
* Author: Pedro Sánchez Ramírez (MrChunckuee)
* Blog: http://mrchunckuee.blogspot.com/
* Email: mrchunckuee.psr@gmail.com
* Description: Basic temperature sensor using the LM35
*******************************************************************************
* Rev. Date Comment
* v0.00 16/104/2018 - Firmware creation
******************************************************************************/
#include <msp430.h>
#include <stdlib.h>
#include "HAL_Dogs102x6.h"
#include "special.h"
#include "imagenes.h"
char temperatureLCD[20];
int adcValue;
uint8_t barTemperatureLevel;
double temperature;
unsigned char muestras, overTemperature;
/********** P R O T O T Y P E S *************/
void MCU_Init(void);
void MCU_Delayms(int16_t time);
void ADC_Init(void);
int16_t ADC_Get(void);
void GUI_Init(void);
void GUI_WelcomeMessage(void);
void GUI_SetTemperature(void);
void main(void){
MCU_Init();
GUI_WelcomeMessage();
GUI_Init();
// Main loop
while (1){
adcValue += ADC_Get();
muestras++;
if(muestras==32){
P1OUT ^= BIT0; // XOR P1.0
muestras=0;
adcValue=adcValue>>5;
temperature = adcValue*0.08;
if(temperature>45)
overTemperature=0xFF;
else
overTemperature=0x00;
barTemperatureLevel=(uint8_t)(temperature-10);
barTemperatureLevel=35-barTemperatureLevel;
SPECIAL_ftoa(temperature, 1, temperatureLCD);
GUI_SetTemperature();
}
if(overTemperature==0xFF)
P1OUT ^= BIT0; // XOR P1.0
MCU_Delayms(32);
}
}
void GUI_Init(void){
// Set default values on LCD
Dogs102x6_clearScreen();
Dogs102x6_imageDraw(barTemp, 0, 0);
Dogs102x6_stringDraw(0, 0, " MSP-EXP430F5529 ", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDraw(2, 4, "Temperature", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDraw(4, 4, " C", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDrawXY(40, 28, ".", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDrawXY(78, 42, "10", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDrawXY(78, 32, "20", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDrawXY(78, 22, "30", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDrawXY(78, 12, "40", DOGS102x6_DRAW_NORMAL);
}
void GUI_WelcomeMessage(void){
// Display MrChunckuee Logo
// and welcome message
Dogs102x6_imageDraw(mrchunckueeLogo, 0, 0);
MCU_Delayms(2000);
Dogs102x6_clearScreen();
Dogs102x6_stringDraw(1, 0, " MSP-EXP430F5529 ", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDraw(3, 0, " Thermometer ", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDraw(5, 0, " @MrChunckuee ", DOGS102x6_DRAW_NORMAL);
Dogs102x6_stringDraw(7, 0, "http://e2e.ti.com", DOGS102x6_DRAW_NORMAL);
MCU_Delayms(2000);
}
void GUI_SetTemperature(void){
// Set temperature on LCD
Dogs102x6_stringDraw(4, 15, &temperatureLCD[0], DOGS102x6_DRAW_NORMAL);
// Set bar temperature on LCD
if(barTemperatureLevel>35){
Dogs102x6_rectangleDraw(92, 15, 93, 50, 1, DOGS102x6_DRAW_NORMAL);
}
else{
Dogs102x6_rectangleDraw(92, 15, 93, 15+barTemperatureLevel, 1, DOGS102x6_DRAW_INVERT);
Dogs102x6_rectangleDraw(92, 15+barTemperatureLevel, 93, 50, 1, DOGS102x6_DRAW_NORMAL);
}
}
void MCU_Init(void){
WDTCTL = WDTPW | WDTHOLD; // stop watchdog timer
// Basic GPIO initialization
// Configure Dogs102x6 ports
P5OUT &= ~(BIT6 + BIT7); // LCD_C/D, LCD_RST
P5DIR |= BIT6 + BIT7;
P7OUT &= ~(BIT4 + BIT6); // LCD_CS, LCD_BL_EN
P7DIR |= BIT4 + BIT6;
P4OUT &= ~(BIT1 + BIT3); // SIMO, SCK
P4DIR &= ~BIT2; // SOMI pin is input
P4DIR |= BIT1 + BIT3;
//General GPIOs initialization
P1DIR |= BIT0; // P1.0 output
P1OUT &= ~BIT0; //Clear LED1
// Set up LCD
Dogs102x6_init();
Dogs102x6_backlightInit();
Dogs102x6_setBacklight(11);
Dogs102x6_setContrast(11);
Dogs102x6_clearScreen();
// ADC Init
ADC_Init();
//Clear values
adcValue = 0;
barTemperatureLevel = 0;
overTemperature = 0x00;
temperature = 0;
muestras = 0;
}
void MCU_Delayms(int16_t time){
int16_t delayCount;
for (delayCount=0; delayCount<time; ++delayCount)
__delay_cycles(1000); // 1ms = 1000 clocks at 1MHz
return;
}
void ADC_Init(void){
ADC12CTL0 = ADC12SHT02 + ADC12ON; // Sampling time, ADC12 on
ADC12CTL1 = ADC12SHP; // Use sampling timer
ADC12MCTL0 = ADC12INCH_6;//5; // Use A6 as input
ADC12CTL0 |= ADC12ENC; // Enable conversions
P6SEL |= BIT6;//BIT5; // P6.6 ADC option select (A6)
//P8DIR |= BIT0; // P8.0 output
//P8OUT |= BIT0; // Set P8.0 high
}
int16_t ADC_Get(void){
ADC12CTL0 |= ADC12SC; // Start reading
while (ADC12CTL0 & BUSY); // Waiting to read
return ADC12MEM0; // Return value on adc
}
view raw MSP-EXP430F5529_008: main.c hosted with ❤ by GitHub
Video:
Here a small video of the working temperature sensor.


Download:
Here the direct link to DOWNLOAD the available files, you can also check or download the information from my repository on GitHub, if you do not know how to download it you can check here, well for now it's all, if you have doubts, comments, suggestions, concerns, etc. leave them and I will try to answer as soon as possible.


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Bibliography:
MrChunckuee

Publicado por MrChunckuee

Amo armar, desarmar y/o destruir cosas en donde la electrónica y los componentes estén involucrados, me gusta la robótica y los microcontroladores, de ahí el nombre de mi blog, el cual surge por la pasión que tengo sobre estos temas: La Electrónica que es mi carrera y la Robótica que es uno de mis hobbies favoritos, siempre he dicho "Casado con la electrónica, pero amante de la robótica".

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