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one wire memory loop?

 
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Scottl



Joined: 21 Feb 2005
Posts: 25

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one wire memory loop?
PostPosted: Thu Mar 20, 2008 9:00 pm     Reply with quote
I have a DS1921G IButton kicking my A**! I have everything working fine but I cannot find a good method for retreiving all the logs.

The logs start at 1000h! I read the mission samples counter which is 24bits unsigned integer and I only read 16bits and then clear the IButton for the next mission.

I am using some code from the forum and I do not remember who posted it but thanks! See sample below:

Code:


unsigned int16 ds1921G_samples()
{
 int8 lsb, msb, csb;  // csb not needed for 16 bits
 unsigned int16 samples;
 float temp_log;

 onewire_reset();
 onewire_write(0xCC);
 onewire_write(0xF0);
 onewire_write(0x1B);
 onewire_write(0x02);
 lsb = onewire_read();

 onewire_reset();
 onewire_write(0xCC);
 onewire_write(0xF0);
 onewire_write(0x1A);
 onewire_write(0x02);
 msb = onewire_read();

 samples= make16(lsb, msb);      // 16 bits

 // Here I want to loop through the memory and get the data and send it to a pc.

for (i=0;i<=samples;++i)
{
 onewire_reset();
 onewire_write(0xCC);
 onewire_write(0xF0);
 onewire_write(?????????);  // Need to loop memory start to end LSB first 1000h
 onewire_write(?????????);  // MSB last starting at 1000h
 temp_log = onewire_read(); // byte

 temp_log = (float) temp_log / 2 - 40; // Maxim Conversion for DS1921G
 fprintf(COM_A, "I%3.1f\r", temp_log);
}



Does anyone have a good method on how I can loop through the LSB and MSB values to command the IButton for the data?

Thanks in advance,

Greg
jma_1



Joined: 08 Feb 2005
Posts: 147
Location: Wisconsin

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PostPosted: Mon Mar 24, 2008 6:02 pm     Reply with quote
Howdy,
I only briefly looked at the data sheet from Maxim. I think you can select the starting address for reading from memory. The flow chart on page 20 looks promising.

Mast Tx -> TA1(T7:T0), TA2 (T15:T8). Target address register indicate memory address to read.

Again, I only quickly scanned the datasheet and probably missed something crucial, but this looks a good path.

Cheers,
JMA
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