No signal of finished conversion while using AD7731

[Mickey_2006]

ad7731

Im' using AD7731 converter with T89C51AC2 microcontroller and I get no RDY pulled down (signal that conversion is finished):

This is the code I use:
(POL pin is tied HIGH)
any ideas why?
Does anyone have code for driving AD7731?

fnSendByteAD7731 (0x02); // Next write to MODE register
fnWait1ms ();
fnSendByteAD7731 (0x50); // First 8 bits of MODE register
fnWait1ms ();
fnSendByteAD7731 (0x70 + (channel & 0x07)); // Last 8 bits of MODE register
fnWait1ms ();

while (AD7731_RDY) _nop_(); // Wait for conversion to end


void fnSendByteAD7731 (unsigned char byte) {
unsigned char cnt;

for (cnt = 0; cnt < 8; cnt++) {
AD7731_DATA = (byte & 0x80) == 0x80;
AD7731_SCLK = 0; fnWait1ms ();
AD7731_SCLK = 1; fnWait1ms ();
byte = byte << 1;
}
}

 

[bobcat1]

Re: 8051 and AD7731

Hi

Connect a scop or a logic analyzer and verifay the signals acording to the data sheet


All the best


Bobi

 

[dpsman]

Re: 8051 and AD7731

Did you check MCLK OUT?
If there is a bug in the code, you should post function implementation in order to get help.

 

[Mickey_2006]

Re: 8051 and AD7731

Here are the functions:

void fnSendByteAD7731 (unsigned char byte) {
unsigned char cnt;

for (cnt = 0; cnt < 8; cnt++) {
AD7731_DATA = (byte & 0x80) == 0x80;
AD7731_SCLK = 0; fnWait1ms ();
AD7731_SCLK = 1; fnWait1ms ();
byte = byte << 1;
}

AD7731_DATA = 1;
}


unsigned char fnReadByteAD7731 () {
unsigned char cnt;
unsigned char result = 0;

for (cnt = 0; cnt < 8; cnt++) {
AD7731_SCLK = 0; fnWait1ms ();
result |= (0x01 & AD7731_DATA);
AD7731_SCLK = 1; fnWait1ms ();
result = result << 1;
}

return result;
}


Do you have any idea what is wrong?