Dual Channel System With PIC16F887

hi there friendZzz...!

I am working on multiple channel ADC to RS232 using PIC16F887
Now the problem is that I want to build dual channel EEG systems which transmit data of both channel to the serial Comm (PC) simultaneously...
Something like this ...

For example: when I get output 8 bits for each channel, the Data bytes should take turns, i.e., I have to program the uC internally to send out the data like this. See below:

EEG Channel A ->
|-->uC / PIC--> Data A, Data B, Data A, Data B, -> uC Serial port
EEG Channel B ->

What i have tried so far is the code below...

unsigned short temp_res;
unsigned short temp_res1;
char buf[7];
char buf2[7];
int i;
void main() {
UART1_Init(19200);
ADCON1 = 0x80;
TRISA = 0xFF;
ANSEL = 0xFF; // Configure AN2 pin as analog
C1ON_bit = 0; // Disable comparators
C2ON_bit = 0;

TRISA = 0x03; // PORTA is input
TRISD = 0; // PORTC is output
TRISB = 0; // PORTB is output


do {
temp_res = ADC_Read(1)>>2 ;
PORTD = temp_res;
ByteToStr(temp_res,&buf2);
temp_res1 = ADC_Read(0)>>2 ;
PORTB = temp_res1; // Send lower 8 bits to PORTB
ByteToStr(temp_res1,&buf);

for(i = 0; i < 7; i++)
{
UART1_Write(buf2);
Delay_ms(10);
UART1_Write(buf);

}
} while (1);
}

The program above shows output on terminal like this 49341
but it must be like this 94143 (because I applied 2.8V on AN0 and 1.85 on AN1)
Sorry,, If I have done something really stupid in the code :-D because I am very beginner for PIC programming so I really need help...
If u ppl can guide me for my purpose in some more better way then I will be really thankful to all of u ...
Thank u ..

Are you trying to accquire the ADC simultaneously, if so, you cannot do it with PIC, as it only allows one channel at a time. You need some ADC chip to do it

I guess buf and buf2 holds the two digital values as string...
Then why you are sending one character from buf and the next character from buf2?
I think you need to send buf full and there after buf2 like:
for(i = 0; i < 7; i++)
{
UART1_Write(buf);
Delay_ms(10);
}
for(i = 0; i < 7; i++)
{
UART1_Write(buf2);
Delay_ms(10);
}

Now if the values displayed are reverse then just reverse the for loop (count down from 6 to 0)

Why my PIC ADC cant read AC (sine wave) inputs.. it is showing wrong code at the o/p even after using level shifter..
I have made VDR circuit as a clamper cirucit ...
Kindly help....! :-|

post your complete code.

Also, what is the range of voltage applying at PIC ADC channel ? (min:max)

And how you are measuring the change at digital o/p?

What about the reference voltage? Is it fixed or variable?

There is my code uptill now...
And the clamper circuit and anti aliasing filter I am using i also here..
When I am changing MCU clock frequency from 8 MHz to 100 Mhz so my signal become much better after ADC sampling (at ADC input) .. But this is too high clock frequency .. ? :shock:
Thank u for the help...

Hi ,, I got it .. see my wave form .. What u say i think now it is sampling good.. :-D
But there is problem with my clamper circuit.. Rite because -ve is still nearer to zero.. :roll: