store string & adc reference help!!!

[desertkids]

hi, now I'm working for my final year project. i need to measure 2 temperature sensor and 1 pressure sensor and transmit the value measured through MU-1-R transceiver. i have write some code for this project. now i face 2 problem, first is for pressure sensor, because the range of pressure I'm going to measure are very small (from 99kPa to 101kPa) and the voltage output also very small (range from 4.11V to 4.17V), so i hope can measure the 0.001V change from pressure sensor, this should be can done by 12bit adc, but my pic18f4550 cant make 12bit adc. so can i measure pressure sensor with voltage reference but measure temperature sensor for 0-5V?(see my code)or can suggest better opinion?

My second problem is how I can store the string into buffer? Lets say I have 20 loop of data. For first data I store at buffer 1, second data store at buffer and so on.

Maybe my explanation not so detail, but I can explain more if need. Please help me, thanks.


#include <18F4550.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#device ADC=10 // define 10 bit resolution
#use delay(clock=20000000)
#use rs232(baud=19200, xmit=PIN_C6, rcv=PIN_C7, parity=n, bits=8, BRGH1OK, stream=UART)
#use rs232(baud=4800, xmit=PIN_D0, rcv=PIN_D1, parity=n, bits=8, BRGH1OK, stream=GPS)

#include <stdlib.h>

#define buzzer pin_b0
#define sw1 pin_b1

#define temp1_ch 0
#define temp2_ch 1
#define press_ch 4
#define acc_x_ch 5
#define acc_y_ch 6
#define acc_z_ch 7

signed int temp_1,temp_2;
float volt_temp_1, volt_temp_2, volt_press,press,;
int n;

float analog_read(int channel);

void main()
{
set_tris_a(0xff);
set_tris_b(0xff);

for(n=1;n<21;n++)
{

//setup_adc_ports(AN0_TO_AN7|VREF_VREF);
//setup_adc(ADC_CLOCK_DIV_64);
volt_temp_1= analog_read(temp1_ch);
temp_1=((float)volt_temp_1-2.73)*100;

//setup_adc_ports(AN0_TO_AN7);
//setup_adc(ADC_CLOCK_DIV_64);
volt_temp_2= analog_read(temp2_ch);
temp_2=((float)volt_temp_1-2.73)*100;

volt_press=analog_read(press_ch);
press=(((float)volt_press-0.204)*21.7865)+15;

fprintf(UART,"\r\ntransmitting...");

fprintf(UART,"\r\n%2d,%1.3f,%3.2f,%1.2f,%d,%1.2f,%d",n,volt_press,press,volt_temp_1,temp_1,volt_temp_2,temp_2);

//store the string in buffer[n](n from 1 to 20)
//sprintf(buff[n],"\r\n%2d,%1.3f,%3.2f,%1.2f,%d,%1.2f,%d",n,volt_press,press,volt_temp_1,temp_1,volt_temp_2,temp_2);

printf("\r\nFINISH TRANS!!!");

delay_ms(2000);
}

//how to print the string that store in buffer 1 to buffer 20 to uart
//for(n=1;n<21;n++)
//{
//fprintf(UART,buff[n]);
//}
fprintf(UART,"\r\nFINISH ALL!!!");

}
}

float analog_read(int channel){

float tmp = 0;

set_adc_channel(channel); // select channel
delay_ms(10);
tmp = read_adc(); // read into volt reg

return (float)tmp/204.6; //(a/(5/1023))
}

[Rohit de Sa]

[asmallri]

[Rohit de Sa]

[crystal_lattice]

your code for the loop is wrong, you will not use the full array size and it will overflow. Use: