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Guido
01-30-2007, 07:41 AM
How many DS18B20 Temperature sensors can be put on the 1-wire circuit....And how in the heck do you identify them...I did read on the specs that each has its own address. Would that same be addresse in the owin and owout?
Thanks
Guido

Franklin
01-30-2007, 09:10 AM
Lots (don't know exactly) but it depends on power and distance also. Each has it's own 64 bit identifier and I would suppose that is what owin/owout is looking for.

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- Stephen

Tracy Allen
01-30-2007, 01:52 PM
Yes, that is the address in the one-wire commands.

One device only, you don't need the address. Use the skipROM command.

If you have one device, you can use the readROM command to discover its address to use in the following situation.

Two or more devices on the same buss, you can use the matchROM command plus the address of the device you want to activate.

If you have multiple devices on the same buss, and don't already know their addresses, there is the searchROM command that you use in a process of discovery to find the addresses of all attached devices. This is a more complicated process.

The number of devices on the buss is limited primarily by the capacitance. There is no practical limit set by the number of addresses.





If there is only one device on the buss, you can use one command to retrieve the address. Once you know

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Tracy Allen
www.emesystems.com (http://www.emesystems.com)

RD
02-08-2008, 11:27 AM
If you have multiple devices on the same buss, and don't already know their addresses, there is the searchROM command that you use in a process of discovery to find the addresses of all attached devices. This is a more complicated process.
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Does anyone know of a pbasic program, floating around,·to do this search?

That is, search through a 1-wire bus, with multiple devices, and identify each device info?

Maxim App Note 187 describes how this is done.· But it's a little beyond me,
unless I abolutely have to...

·

terry_bear
02-08-2008, 11:05 PM
RD,

Yes there is.. it is in one of The "Nuts and Volts" columns. It is actually a group of 3 (I think)linked programs, one of which is called OWsearch. One prog. looks at the One Wire buss and looks for devices; one stores the device IDs in EEPROM (if I remember correctly) and one reports the device IDs

RD
02-09-2008, 02:36 AM
>>>It is actually a group of 3 (I think)linked programs...

I've·looked at·this above·and I think it only checks the info of one device at a time.
I could be looking at someting else.

In any case, I've found another program that does what I want.

When or if I can translate it into pbasic I will post it.· I only have one
type of device, the DS18B20, so I'm not sure how I will test it.


Thanks.

Paul Sr.
02-09-2008, 02:55 AM
There is some great information on Peter Anderson's site (www.phanderson.com) on this subject. If you select the TM 128, there is a lot of detail that will answer your questions.

terry_bear
02-09-2008, 07:54 AM
RD,

Actually, OWsearch will identify at least eight, from personal experience. <grin> Most of them were DS1820s, but there was a DS1620 and one or two others, all on-line at once...

Terry