Temperature Sensor Not working

[chandrasekaran]

Hi al,

For the past 2 days i am trying to read the value from temperature sensor ds18b20.But i didnt get the any values.i have few doubts.Actually i am connecting ds18b20 with renesas controller(r8/tiny series).

Normally in renesas controller if a pin is made as input.we need to enable pullups.
My doubt is..
In the sensor pdf, they have mentioned to connect pullup for DQ pin(data pin).So i connected 4.7k to VCC.But is it necessary to use both the pullups(internal pullup of controller+DQ pin pullup)?

Also in sensor pdf they mentioned about time delays for reading the values as well as writing the values..I am not giving delays less than what they have mentioned.But i have given delay more than that..Suppose if they have mentioned to give 1usec delay means i had given 10 usecs.Will it cause any problem?

 

[FvM]

Suppose if they have mentioned to give 1usec delay means i had given 10 usecs.Will it cause any problem?

In some places, yes. Study the 1-wire protocol specification to understand the required timing - or implement the protocol as specified.

 

[Tahmid]

The external pull-ups shouldn't be required as internal pull-ups already exist. And study the 1-wire protocol. You could also use LM35/LM335 for temperature measurement. These give linear output. Or the TC72 which uses the SPI protocol.