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John A. Zoidberg
02-26-2012, 10:21 AM
Hey there ladies and gentlemen,

I'm reproducing one of the example circuits in an old book by Myke Predko "Programming and Customizing the PIC Microcontroller", and found a simple temperature sensor based on the DS18S20.

However, due to the RTOS inside in the particular system, bit-banging is a no-go, I tried doing that and it stalled the system pretty badly.

So, by using hardware UART, I may be able to sample the temperature easily, but in the Maxim's application note: http://www.maxim-ic.com/app-notes/index.mvp/id/214 I need a open-drain buffer.

Unfortunately I may not be able to get 2N7002 in my place, or those specialized drivers mentioned inside. Could I just use a non-inverting buffer (CD4010) to replace these instead?

jmg
02-27-2012, 08:38 AM
Unfortunately I may not be able to get 2N7002 in my place, or those specialized drivers mentioned inside. Could I just use a non-inverting buffer (CD4010) to replace these instead?

Sure. Speed is not really an issue, just check the drive margin, as Voh may be on the minimal side. Depends on the Brand, NXP were better IIRC at minimal drives.

If you have spares in the package, I'd parallel them.

John A. Zoidberg
02-27-2012, 12:00 PM
Sure. Speed is not really an issue, just check the drive margin, as Voh may be on the minimal side. Depends on the Brand, NXP were better IIRC at minimal drives.

If you have spares in the package, I'd parallel them.

Hello,

I got that, and the Atmel's application note seemed to use only two transistors: www.atmel.com/Images/doc2579.pdf.

However, since the one-wire routines are not RTOS-friendly, I guess I may have to use a seperate microcontroller (like a PIC12F) to control the DS18B/S20 instead. :D

OppaErich
02-27-2012, 02:21 PM
There are OneWire bus masters for UART, IC and SPI. I was looking for a IC one but didn't want to buy 1900 :( Maybe you can find the UART one in smaller quantittes.