Reading multiple DS18B20's on a single pin using 18M2.

#1
I realise that the 18M2 doesn't support owin & owout. Has any one written code that will allow the DS18B20 to be read & written to for the reading of 12 bit temps.
I have read the serial # of 4 devices. How do I send the command to read each device . RoscoW
 
#3
All the pins on the 18M2 are committed except B.0. I only have 18M2's on hand. Instead of trying to do it myself I just wondered if others have written the code. Why reinvent the wheel. I have used the Readtemp12 command and get valid data. The PCB is designed & made
 

hippy

Technical Support
Staff member
#4
Unfortunately the DS18B20's use high-speed signalling which is too fast for a PICAXE to bit-bang from a user's program. 1-wire commands are bit-banged from within the firmware rather than using an on-chip peripheral so the only way to access 1-wire devices is through the 1-wire commands provided. That means multiple DS18B20 on a single pin for the M2's is not possible.

The only practical way to do it would be to move to an X2 PICAXE or add an additional PICAXE which can read multiple DS18B20's and provide the results via a single pin.
 
#6
Thanks. The DS2482 will require a bit of hardware hacking but should solve the problem. Didn't know of the DS2482. New to OneWire & i2c buss.
Regards RoscoW
 
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