Multiple DS18B20 on one input pin

[Christian177]

Hi all,

I am completely new to PicAxe and to this forum, so my problem may sound a bit silly to you!

I have started with a 08A and want to connect digital temp sensor DS18B20. No problem reading the individual code of the sensor using readowsn, also no problem reading the temperature of the device using either readtemp or readtemp12.
Now I'd like to connect multiple 18B20 to the same input. How can I address each of them one by one and read their temperature value? Is this possible, and if so how do I program this?
I have all other PicAxe chips as well, so no problem if I need to upgrade to a bigger one to solve this problem.

Many thanks for help!

Chris

 

[hippy]

Welcome to the PICAXE Forum.

You can only read multiple DS18B20 temperatures on a single signal line by using the OWIN and OWOUT commands so you will need to use an X1 or X2 PICAXE.

 

[manuka]

a 08A

Is that a typo for 08M ??? If so it won't be up to it. You may want to check past mentions of reading multiple DS18B20s

 

[westaust55]

Manuka's link should be: http://www.picaxeforum.co.uk/showthread.php?t=7739

and here is another thread I recalled where multiple devices were used/attempted in one-wire mode:
http://www.picaxeforum.co.uk/showthread.php?t=11100
multiple DS18B20's were working and eventually (but no final code posted) for using the DS2482-100 i2c to own-wire bus master also was working.

 

[hippy]

http://www.picaxeforum.co.uk/showthread.php?t=11100

rmeldo's post #4 looks to be what we have tried and tested and have shown to work.

It is also possible to issue One-Wire commands to initiate temperature readings for each DS18B20 in turn, delay a single 750ms, then read the results back in turn. This minimises the delay between readings, it also means the program can continue doing whatever it needs to do with no delays, reading the results 750ms or longer later.

 

[Christian177]

Hi all,

many thanks for your good advice. I have looked at all the responses and threads and will try a few things next, first of all the owin and owout commands.
Oh yes, and 08A was in fact a typo! I meant to say 08M!

Again many thanks!

Chris