Measure Command

Forum for the Open GPS Tracker

Measure Command

Postby Sleepydog » Mon Sep 08, 2008 1:19 am

I got this working pretty well today and wanted to write up my findings for Mike's documentation. Please feel free to comment and correct where necessary.



Sending the tracker the command "GPS MEASURE" returns a text message with "MEASURE" and 6 numerical values shown in the example text message:
"MEASURE 1023 1023 1023 1023 540 303"

Numerical Values
Each of the values is a number between 0 and 1023 and represents an analog to digital conversion of the voltage measured on the input pin. Five inputs are available, the sixth number is the reading of an internal temperature sensor in the ATTiny84.
Ground returns close to zero (14 on my tests)
+Vcc and open pins return (due to an internal pull up resistor) 1023
The Temperature sensor reads approximately:
0 degrees...(my batteries didn't like being frozen - no data)
40 degrees..284
70 degrees..303

Analog Inputs
The five available inputs on the ATTiny84 are shown here with the associated port designations. Pins 10 and 6 are available for use in the original OpenTracker schematic. Pins 7, 8 and 9 are connected to the ISP Programming header. Using the ISP header to connect to an Input/Output circuit board would be a useful way to expand the OpenTracker since +Vcc, Ground and three I/O pins are available on the ISP header.
Here is the order the inputs are reported in the MEASURE text message:

A - ATTiny84 Pin 10, Port A3
B - ATTiny84 Pin 9, Port A4, ISP Header Pin 3
C - ATTiny84 Pin 8, Port A5, ISP Header Pin 1
D - ATTiny84 Pin 7, Port A6, ISP Header Pin 4
E - ATTiny84 Pin 6, Port A7
F - ATTiny84 internal temperature sensor
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Re: Measure Command

Postby comp850 » Fri Nov 27, 2009 1:30 pm

Thought I would mention that I saw on Page 144 of the manual that Mike posted,, has some interesting things about the temp sensor.

I am getting about 316ish..for 70F though I am running @ 5v
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Location: Spokane, WA

Re: Measure Command

Postby Mike » Fri Dec 18, 2009 9:16 am

The temp sensor is not very good, but since it was there I supported it.
Note the measure also works on the ATMEGA88.
I did not find a good way to measure the battery voltage, without an extra transistor.
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