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problem using AD7711A, a 24 bit analog to digital converter

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Nicolina2

Nicolina2

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Hi!
Somebody have experience using AD7711A, a 24 bit analog to digital converter?
I have a problem somewhere, because I can't see the right data on a LCD display... the good value is just in flashing at 2 - 3 second on LCD display ... in the rest, the measured value of analogic signal is 0.

The AD7711A is conected at a AT89C2051 microcontroller, and this one display data on a LCD with 2 lines, compatible with HD44780 standard

In infinite while loop I have:
while(1)
{

write_to_ADC(0xA097D0); // initialization code, mean Activate BAckground Calibration, gain 1, chanel 0, Unipolar, and the number at Filter Selection is 2000

if(flag_received_data24 == 1)
{
display_no(curent_data24);
flag_received_data24 = 0;
EX0 = 1; // enable int0
}
}
the external interrupt 0 is:

void int_ext_0(void) interrupt 0
{
EX0 = 0; // invalidarea intreruperii externe 0
curent_data24 = read_from_ADC();
flag_received_data24 = 1;
}
and the reading and writing to AD7711A functions are:


void write_to_ADC(unsigned long int data24)
{
long int compara,numarat;
TFS = 1; RFS = 1; SCLK = 0;
TFS = 0;

compara = ((unsigned long)1)<<23;
for (numarat=compara;numarat>0;numarat>>=1)
{
if((data24 & numarat)==0) SDATA = 0;
else SDATA = 1;

SCLK = 1;
SCLK = 0;
}
TFS = 1;
}

unsigned long int read_from_ADC(void)
{
unsigned char i;
unsigned long int data24;
data24 = 0;
TFS = 1; RFS = 1; SCLK = 0;
RFS = 0;
for(i=0;i<24;i++)
{
SCLK = 1;
data24 = data24 | SDATA;

SCLK = 0;

data24<<=1;
}
RFS = 1;
data24>>=1;
return data24;
}
I put on attachment the a jpeg with the schematic... but if you want to help me,
I can send you the full source code, just write me at hai@k.ro

I am in the situation: all is perfect but is not working...
PLEASE HELP ME! :cry:

Stelian
 

Re: problem using AD7711A, a 24 bit analog to digital conver

Could be that you have one of the "famous" 8051 problems that a PORT can be used as input or output :)

In your read_from_ADC function set SDATA=1 somewhere in the beginning otherwise you just might read 0 if the last bit written to SDATA using write_to_ADC was 0 ...

I also moved this thread to the Microcontrollers section.

hope this helps and best regards
 

    Nicolina2

    Nicolina2

    Points: 2
    Helpful Answer Positive Rating
Re: problem using AD7711A, a 24 bit analog to digital conver

THANK YOU VERY MUCH C-Man !

This was the solution!
I just put a SDATA = 1; on the begining of reading function...and ALL is working.

I am feel like indebted by you, because I had a pain to fix the problem
for 2 days... and in this morning... after a half of hour from posting my message
on list, I got the solution!

I am looking now on the LCD display... and I not belive that is working... 8O


Thank you! again... :lol: and.. if I can help you with something... don't hesitate to ask! :wink:
 

Re: problem using AD7711A, a 24 bit analog to digital conver

Glad to hear that it is working now :)

Just one note to you (and others) there is a "that helped" button in each thread that only the starter of the thread can see. Whenever you get a helpful answer press this button and you will donate 3 points to the helpful person.

Also note that the points are not subtracted from your account ...

best regards
 

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