[SOLVED] Problem in receiving data from DS18b20

I am working on one wire protocol based temperature sensor ds18b20 which is powered by external source. First i am resetting DS18b20 and then i am sending skip ROM command ie CCh followed by 44h i.e. temperature conversion. Datasheet says that if the temperature conversion is in progress then DS18B20 will send zero else one. But in my case i am only receiving zero.


Plz help

After 'reset' do you check 'presents' pulse?

Hi,

Circuit.
Scope pictures with voltage levels and timing.

Klaus

yes.... and also i DS18b20 is responding with zero.

First check if you are getting a presence pulse after the first reset and before sending the commands. It sounds like a complete communication failure.

Are you using the DS18B20 with it's own power source or in parasite power mode?
What value pull-up resistor are you using?

Brian.

i have attached the circuit diagram.

Yes i am getting the presence pulse after the first reset.
I am providing external power to DS18b20 with 4.7k pullup resistor.

No reason to try get any data without getting 'presents' pulse. Anyway, you didn't provided anything. That means that you don't realy need to solve you problem and we a not able to force you to do that.

Easyrider83 said:

No reason to try get any data without getting 'presents' pulse. Anyway, you didn't provided anything. That means that you don't realy need to solve you problem and we a not able to force you to do that.

Click to expand...

i am getting the "presents" pulse from DS18B20. I have attached the circuit diagram and datasheet of DS18b20 and also code for writing and reading for DS18b20 using assembly language. I am using AT89S52 microcontroller and p3.1 as DQ pin of DS18b20

Sorry Mr Easyrider....i have attached the document but it disappeared...again i have attached the document please find it

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In the datasheet it is mentioned that after sending 44h to DS18b20, it will respond zero if temperature conversion is taking place and one if it is completed. My question is after sending 44h what should be the status of DQ pin means i should release it or make it low.??.

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plz help.....i am not receiving data from ds18b20...

i am getting the present pulse then i am sending cch followed by 44h for skip rom and temperature conversion (as i am providing external supply to ds18b20), but the problem is, in the datasheet it is mentioned that ds18b20 will sent "0" if the temperature coversion is in progress while "1" if the temperature conversion has completed after sending 44h to ds18b20.

What is the problem..??

Finally got the output.......i have done mistake in "reading" part.....thanks all