Quote:
Originally Posted by GvilleRenovator
... I just ordered my Logomatic and several 1 wire temperature sensors. I will post my findings/experimenting on your DIY Data Logger thread.
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Well, if it helps, here's what I know about '1-Wire'
- 1-Wire actually requires at least two wires and probably even better, three wires. You gotta have at least a data wire (which has a small amount of voltage), and a ground wire. There's an operational mode (paricitic) wherein a small capacitor that is internal to the 1-Wire chip stores electricity that is 'borrowed' from the data line, and this charge is used to run the chip. Because it takes some amount of time for the capacitor to store enough power to execute a request for data and to write data, there is a limit to the frequency of data requests/writes. There is another mode wherein the 1-Wire chip uses a data wire, a ground wire and a dedicated power wire. in this mode, you can make data requests as often as you wish, limited only by the chip's ability to recognize and respond to a data request.
- Each 1-Wire device on a string is hard-coded at the factory with its own unique identifying number. When there is a request for data, all devices read that request and look to see if their unique ID number is contained in that request, if it is, then that chip will respond, if not then no response.
- To send a request to the chip, and to read the response from the chip, some device that can be programmed to provide the proper timing and instruction sequencing and response reading, is required. I looked to see if there was a set of chips that had these routines all pre-written and ready to go. I wasn't able to find such a thing, with the exception of a chip that would send out the instruction string with the correct timing and instruction sequence. This instruction sending and data recieving is the kind of thing that microprocessors like the Arduino (the Logomatic uses the ARM processor, which is also a good choice) are good at doing. I found websites that had examples of 1-Wire code that could be incorporated into a C source code that would then have to be compiled and loaded into the Arduino. There is an Arduino group here in town (there's a good chance that there's one in your town, too) that has a good bit of expertise in these matters, and they are friendly and ready to help. There are also on-line groups who are also friendly and ready to help.
... but I was so busy, busting my butt, trying to get the loop field in before the rains began, that I couldn't take the time to learn the fine points of the Arduino (or the ARM) design cycle.
Hope this helps...
Regards,
-AC_Hacker
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