10 bit A/D on 12F675 not working

[Nathan Meyer]

I am using the PIC12F675 that is suppose to have a 10-bit A/D. So in the program I have a variable, Voltage, that is set up as a long. In the program I set the channel and do a "voltage=read_adc()". However, I do not get a 10-bit number, instead it only reads a 8-bit value. I have seen that there are some problems with the 12F675 and the CCS compiler. Does anyone know if this is a compiler problem or am I doing this wrong? See code below.

#include "12f675.h"
#use delay(clock=4000000)
#fuses INTRC,PUT,BROWNOUT,WDT,NOMCLR

#use fast_io(A)
#define vbat PIN_A0 //battery voltage input
#define isns PIN_A1 //current input
#define soc PIN_A2 //capacity output
#define on PIN_A3 //charge/discharge pin

#define caplo 0
#define caphi 1
#define mult 128 //charge multiplication factor
#define multd 130 //discharge multiplication factor

long on_time,capacity,sum; //variable setup
long prod,percent,crnt,voltage;
long design_cap=3200;
char loop,count;

#int_timer0 //timer 0 interrupt
timer0_isr() //this routine will toggle the
{ //output for the soc

restart_wdt();
count=count+1; //loop counter
if(!loop)
{
if(on_time==0)
{
loop=0;
count=count+1;
}
else
{
output_high(soc); //turn output high
set_timer0((2560-on_time)/10); //set timer
loop=1;
}
}
else
{
if(on_time>=2500)
loop=1;
else
{
output_low(soc); //set output low
set_timer0(on_time/10); //set timer
loop=0;
}
}
}

////////////////////////////////////////////////////////
void main()
{

setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_DIV_2);
setup_vref(false);
set_timer0(0);
port_b_pullups(false);
setup_counters(RTCC_INTERNAL,WDT_2304MS);
setup_timer_0(RTCC_DIV_128);
setup_timer_1(T1_DISABLED);
setup_comparator(FALSE);
enable_interrupts(INT_TIMER0);
enable_interrupts(global);

set_tris_a(0b00101011);

loop=0;
count=0;
sum=0;
prod=0;
capacity=0;

while (true)
{
set_adc_channel(0);
delay_us(100);
restart_wdt();
voltage=read_adc(); //read battery voltage
set_adc_channel(1);
delay_us(100);
restart_wdt();
crnt=read_adc(); //read current
if(voltage<=174&&crnt<=4) //adjust capacity if wrong
capacity=0;
if (voltage>=210&&crnt<=4&&capacity<=875) //adjust capacity if wrong
capacity=875;
percent=((capacity*11)/design_cap); //calculate on time based on
on_time=percent*233; //current capacity and design capacity
while(input(on)) //cahrge accumulation
{
if(count>=55) //consitutes one second
{
count=0;
delay_us(100);
restart_wdt();
voltage=read_adc(); //read voltage
set_adc_channel(1);
delay_us(100);
restart_wdt();
crnt=read_adc(); //read current
delay_us(100);
restart_wdt();
sum=crnt*mult; //current reading times mult factor
prod=sum+prod; //add up the capacity
if (prod>=36000)
{
prod=prod-36000; //reset
capacity=capacity+1; //increase capacity by one
if(capacity>=3300)
capacity=3300;
}
if(voltage>=233&&(9>=crnt>=4)) //adjust capacity if wron
capacity=3210;
}
restart_wdt();
//write_eeprom(caplo,0x00);
//write_eeprom(caphi,0x00);
}
while(!input(on)&&crnt>4) //discharge subtraction
{
restart_wdt();
if(count>=55) //55 times through timer = 1 sec
{
count=0;
set_adc_channel(0);
delay_us(100);
restart_wdt();
voltage=read_adc(); //read voltage
set_adc_channel(1);
delay_us(100);
restart_wdt();
crnt=read_adc(); //read current
sum=crnt*multd;
prod=sum+prod; //add up current
if(prod>=36000)
{
prod=prod-36000; //reset
capacity=capacity-1; //decrement capacity
if(capacity==0 || capacity>=3305) //adjust capacity if wrong
capacity=0;
}
if(voltage<=170) //adjust capacity if wrong
capacity=0;
}
}

}
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 11925

[PCM programmer]

:=I am using the PIC12F675 that is suppose to have a 10-bit A/D.
-------------------------------------------------------------

You need to tell the compiler that you want the 10 bits.
Do this with a #device statement. Put this line immediately
after the #include statement for your PIC.

#device adc=10

While looking at your code, I noticed some other problems.
You have this line:
setup_adc(ADC_CLOCK_DIV_2);
If you read the data sheet for the 12F675, in Table 7-1,
it shows a chart of the proper A/D clock divisor, based
on your crystal frequency. You're using a 4 MHz crystal,
so it shows that a divisor of 8 would be best. So do this:
setup_adc(ADC_CLOCK_DIV_8);


Also, some of your comparison code might not be correct.
I invite you to run the following test program.

<PRE>
#include "16F877.h"
#fuses HS, NOWDT,NOPROTECT,PUT,BROWNOUT, NOLVP
#use Delay(clock=8000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

main()
{
char c;
char i;

printf("1st test:\n\r");

for(i = 0 ; i < 15; i++)
{
if(9 >= i >=4)
printf("i = \%d (within range)\n\r", i);
else
printf("i = \%d \n\r", i);
}

printf("\n\r");
printf("2nd test:\n\r");

for(i = 0 ; i < 15; i++)
{
if((9 >= i) && (i >=4))
printf("i = \%d (within range)\n\r", i);
else
printf("i = \%d \n\r", i);
}

while(1);

}

</PRE>
___________________________
This message was ported from CCS's old forum
Original Post ID: 11926