John's Ramblings » TMB880CF http://john.crouchley.com/blog Personal record for family and friends - contact me: john at crouchley.me.uk Fri, 03 Feb 2012 13:30:18 +0000 en hourly 1 http://wordpress.org/?v=3.2.1 Arduino interface to TMB880CF http://john.crouchley.com/blog/archives/231 http://john.crouchley.com/blog/archives/231#comments Thu, 04 Jun 2009 18:15:57 +0000 john http://john.crouchley.com/blog/?p=231 I found an old LCD thermometer – got it from Maplin many years ago. I hunted for specs on the web but all I could find was that it used a serial data stream. It runs from 1.5V so I used an NPN transistor and a schmitt trigger NAND gate (old 74LS132 chip I had) [...]]]> I found an old LCD thermometer – got it from Maplin many years ago. I hunted for specs on the web but all I could find was that it used a serial data stream. It runs from 1.5V so I used an NPN transistor and a schmitt trigger NAND gate (old 74LS132 chip I had) to interface through to 5V (note to self – I need to find a program to draw my circuit diagrams so I can publish them). I used interrupts on the falling clock pulse to get the data. The Arduino code is here.

From Richard Norman on forums.parallax.com
The thermometer device measures the temperature every 10 Seconds and outputs
the data as serial data as 13 pulses on two pins as follows:
Thermometer Pin 9 (Data out):
Thermometer Pin 10 (Clock Pulses Out):
With the exception of the first clock pulse (which has a duration of 1mSec),
the clock pulses occur 0.125 mSec after the start of the data pulse and last
for 0.125 mSec.
The data bits have the following significance:
D01 – Degrees Celcius Polarity
D02 – 80
D03 – 40
D04 – 20
D05 – 10
D06 – 8
D07 – 4
D08 – 2
D09 – 1
D10 – 0.8
D11 – 0.4
D12 – 0.2
D13 – 0.1

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