10bit a/d conversion

[young]

I have the following program:
#if defined(__PCM__)
#include <16F877a.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 12

#include <lcd420_1.c>
#include <math.h>
void main() {

int i, min, max;
int16 val1,val2,val3;
float Total;

lcd_init();
//lcd has to be cleaned before corectly position data on it
printf(lcd_putc," ");
lcd_gotoxy(1,1);
printf(lcd_putc,"Avitech LLC:");

setup_port_a( ALL_ANALOG );
setup_adc( ADC_CLOCK_INTERNAL );
// set_adc_channel( 2 );
do {
set_adc_channel( 1 );
delay_ms(1);
val1 = Read_ADC();
lcd_gotoxy(1,1);
printf(lcd_putc,"Red:%3u",val1);
set_adc_channel( 2 );
delay_ms(1);
val2 = Read_ADC();
lcd_gotoxy(9,1);
printf(lcd_putc,"Blue:%3u",val2);
set_adc_channel( 3 );
delay_ms(1);
val3 = Read_ADC();
lcd_gotoxy(1,2);
printf(lcd_putc,"Green:%3u",val3);
Total=(float)(val1+val2+val3)*3/255;
lcd_gotoxy(10,2);
printf(lcd_putc," T:%4.2f",Total);

} while (TRUE);
}

I want to get 10 bit resolution conversion, but I just got 8 bit conversion, how to change it and get 10 bit conversion

[valemike]

[BT]

I always use the following in my #DEVICE statements:
#DEVICE ADC=10

But don't know what the default is if this is omitted .....

HTH

[young]

I added #device=10,
but how to use the printf in my case
printf(lcd_putc,"Red:%3u",val1) error occured format type is invalid.

[valemike]

I haven't done any LCD-printf() statements, but this is what I do to print my 16 bit values to Hyperterminal:

printf("A/D value = 0x%lx\r\n", ad_value);

similiarly, you can write: "AD = %ld\r\n", ad_value);

where ad_value is a "long" (aka "int16"). The important thing to note is that you need the "l" (lower case L) after the % to denote that it is a "long".

[young]

When I use printf(lcd_putc,"G:%4x",val1);

the out put is 00fc, the high bits are 00 and lower bit are some value, it is not a ten bit value ( it is always lower than 255). what is wrong?

[rnielsen]

You need to specify to print a LONG hex value. A simple %4x will tell it to print an 8bit value. Try this:

printf(lcd_putc, "G:%lx", val1);

That should enable you to print a 16bit value

Ronald

Smile, it will make people wonder what you've been up to.

[young]

Thank you, NOw I am able to print out correct readings for val1, val2, and val3, however the calculation for T=(float)(val1+val2+val3)*3/1024 return wrong result as T sametime over 5.0, (should be lower than 3.0) what happened here?

[young]

Sorry, it is my misumderstanding, it is correct. since each of the val1, val2, val3 is less than 1024 than the (val1+val2+val3) less than 3*1024, then divided by 1024 should be less than 3, and 3*3 equals 9.

[Humberto]

BT wrote: