1wire DS18s20 and x1 parts

Guys,

Now that the X1 parts support true 1 wire - does this also mean that they will support the DS18s20 (in a multi drop configuration ?)

regards

Craig

Yes, you can use any 1-wire part (including DS18s20) using owin/owout commands, and if you use 'match rom <serial number>' (rather than using 'skiprom') you can have multiple parts on a bus.

The easiest way to find the part's unique serial number is to build a test rig and use the readowsn command on each part individually.

Thanks Technical, will give it a go as i have 1/2 dozen of them donated to me

Craig

Double check- you DO mean &quot;<b>S </b> &quot; &amp; not just the regular DS18<b>B </b> 20 will now be supported?

With the owout and owin commands, I believe you can interface with the entire Dallas 1-W family.

For example, the DS2438 (Temp and A/D), DS2450 (Quad 16-bit A/D) and DS2423 (Dual 32 bit counter).

And, of course the DS18S20. However, for resolution better than 0.5 degrees C, a (x-y) / x calculation is required. If you can live with the 0.5 degrees C, you can use the existing command for the DS18B20 and shift the bits. (Search the Yahoo group on &quot;DS18S20&quot.

PHAnderson

A bit more.

For multiple devices on the same signal lead, you can go through the process Technical describes. Do ReadROMs on all of the devices alone, save the addresses (serial numbers) and then use the MatchROM mode.

I don't believe that new devices will support the SearchROM mode as this requires sending and reading one bit (as opposed to a byte) signals.

PHAnderson

You can send one bit - see the owout command options. We''ve actually done a ROM search and identified parts using the scratchpad memory and an X1, but its quite complicated. We will get around to writing it up in a useable form one day.

However we didn't actually find it very useul for temp sensors anyway! You know you have 5 sensors on the bus and you have 5 serial numbers to play with - but which one is which....????

Testing each one individually (by owin/owout, or more simply with readowsn) is better as you can then identify the serialnumber of each unique part.

Technical, details of the rom search would be very much appreciated as I'm still gazing blury eyed at the DALLAS flow diagram.

Granted, initially it may not be obvious why you would want a string of sensors without knowing which is which but such an arrangement can be useful.
One particular use is a &quot;probe head&quot; containing several (2 or 3) DS18B20s for improved resolution and temperature averaging. This would be a unit manufactured in isolation and only have the three wires available. Rom search would be the only way to address such a device.

Another methodology I've been toying with is the ability to add extra sensors to an existing line of sensors as part of a setup routine. This would work as follows:-
Start setup, user is requested to connect sensor 1. Rom search identifies and records position and SN of sensor 1. The user is then requested to add sensor 2 to the same line, again rom search is used to identify it and note the SN (together with position) and so for as many sensors required.

The alternative to this as you have suggested is to have a dedicated &quot;sensor ID socket&quot; on the main unit. A setup routine is entered to identify the SN and then the sensor must be moved from the &quot;sensor ID socket&quot; to it commisioned socket.
Both approaches are open to &quot;user abuse&quot; but I feel that adding the sensor to its correct location during the setup phase would be less prone to user error. So, please, ROM search method would very nice to have, thanks.

Thanks for the feedback and answers everyone.

Yes Manuka i did mean the 18S20.

regards

Craig