 |
 |
| View previous topic :: View next topic |
| Author |
Message |
densimitre
Joined: 21 Dec 2004
Posts: 45
|
| Read external 10-bit ADC |
 Posted: Tue Jun 07, 2005 10:55 am |
 |
|
Hi
I have a TLC1541 (texas Instruments) 12 channel/10-bit ADC. Interface serial
http://www.lierda.com/upfile/1074129861.pdf
Im using 16F84a, PIN_A4 is pull-up(ed). I want read channnel 0....my rutine to read 10 bit is:
Main.c
| Code: |
#include <16f84a.h>
#use delay(clock=4000000)
#fuses XT,NOWDT,NOPROTECT
#use RS232(BAUD=9600, BITS=8, PARITY=N, XMIT=PIN_A2, RCV=PIN_A4, RESTART_WDT)
#include "TLC1541.c"
float valor;
long adc_result;
void main() {
for(;;) {
adc_init();
set_adc(0);
read_adc();
printf("A/D Conversion using TLC1541\n\r");
value=(float)(adc_result*25)/(float)1024; // 0-25 Volt measure
putc(13);
printf("HEX Value of adc_result=%lX\n\r",adc_result);
printf("Channel 0 Voltage= %2.2f Volts.\n\r",value);
}
}
|
TLC1541.c
| Code: |
void delay() { // Delay.
delay_us(10);
}
void Clock() { // Clock signal generation
output_high(AD_CK);
delay();
output_low(AD_CK);
}
void adc_init() {
output_high(AD_CS); // Be sure TLC1541 is not activated
delay_us(10);
output_low(AD_CS); //Activate TLC1541, CS=0.
delay();
Clock(); //Valid (High to LOW) transition of CS
Clock(); //need 2 "rising edge" of AD_CK
//then 1 "alling edge".
delay();
}
void set_adc(int ch) { //Set ch selection
int i; // AIN0-10
for (i=0;i<4;i++) { // 4 "rising edges" of I/O CLOCK. MSB first
output_bit(AD_DI,shift_left(ch,1,0));
Clock();
delay();
}
for (i=0;i<5;i++) { //Start sample cycle. The 10° clock is
//controled by read_adc();
Clock();
delay(); // to A/D conversion star at any time
}
}
void read_adc() {
int i;
Clock(); //10° Clock
delay();
output_high(AD_CS); //CS=1 when I/O and System clock
//is same pin.
for(i=0;i<44;i++) { //of datasheet, 44 clock cycle for
//finished conversion
Clock();
delay();
}
output_low(AD_CS); //Activate TLC1541 again to read
//10 bit result stream.
for(i=0;i<9;i++) { //Start adc reading, 9 clocks
//(10 bits). Read MSB first
shift_left(&adc_result,2,input(AD_DO));
Clock();
delay();
}
output_high(AD_CS); //TLC1541 is no active. End od reading.
} |
I canīt read the 10 bit result...adc_result= 0x0000 forever......why???
Help me please
Thank you[/url]
Last edited by densimitre on Tue Jun 07, 2005 2:34 pm; edited 4 times in total |
|
 |
bfemmel
Joined: 18 Jul 2004
Posts: 40
Location: San Carlos, CA.
|
|
| Posted: Tue Jun 07, 2005 11:31 am |
|
|
densimitre,
You certainly don't give us much to go on. I need to make a lot of assumptions about what I think Clock() and delay() do in the code. One thing I see is that you are raising AD_CS high after 10 clock cycles. First of all it is active low so you should be setting it low and secondly it should be before the clock cycles and the four bit address of the channel should be on the bus at that time which since you want channel zero might be OK anyway. Just make sure that the adress input is low during this time.
If you can give us more of your program, such as the missing routines and the main body of the program we can probably make some more observations.
Good Luck
- Bruce |
|
|
densimitre
Joined: 21 Dec 2004
Posts: 45
|
|
| Posted: Tue Jun 07, 2005 11:17 pm |
|
|
Hi
I made a change on TLC1541.c
| Code: |
void set_adc(int ch) {
int i;
for (i=0;i<4;i++) {
if((ch&0x8)==0)
output_low(AD_DI);
else
output_high(AD_DI);
ch <<= 1;
Clock();
delay();
}
}
|
Now I can store adc_result...and in my protoboard i had tested it, now its working.....
WOW
Thank you ...
Bye |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
