> -----Original Message-----
> From: marco genovesi [SMTP:marco.genovesi@LIBERO.IT]
> Sent: Thursday, March 07, 2002 2:14 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC]:  mini 16F876 datatogger
>
> A newbie question.
> I would like to build  a very small, cheap and easy to-assembly
> temperature
> datalogger (about 1" x 2" sized) to use for a strange problem. Due to the
> small size, I'm thiking to use only a single PIC chip (no external
> EEPROM).
> Probably a smaller size will be possible using an 8pin PIC and a serial
> eeprom as 24LCxx, but I have some 16F876 and I want use them. These are my
> specs:
>
> -  Size 1" x 2" (about)
> -  32Khz clock
> -  Temp.measure with a thermistor.
> -  one 3V lithium cell
> -  >= 2 months operativity
> -  >= 150 bytes data storage
>
> My doubts:
> 1) Is it really useful to store the temp. data in the 256 EEPROM bytes of
> '876?
> 2) Is it possible to store the data also in an (unused) area of the
> program
> memory?
>
You will need the 16LF876 to run reliably at 3 volts.  Personaly I would use
a smaller pic and some external serial EEPROM which I would power from a pin
in the PIC.  This way the memory can be shut down after writing for power
saving and you get the option of using a large memory.  Depending on your
accuracy requirments, you may not need a PIC with an AD converter, you can
use the simple single slope software ADC shown in Microchips application
note AN512.

Regards

Mike

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