#2200087-Serial-Protocol

The 2200087 is an inexpensive DMM sold at radioshack. It supports logging and graphing data on a computer, but the supplied code only supports Windows. This is a python script to allow for connecting to the multimeter over USB on Linux or Mac OSX. Due to radioshack not supplying any serial specifications, the below protocol was reverse engineered from simply observing the output of the DMM.

#Installation and Usage

Start by cloning this repository:

git clone https://github.com/ddworken/2200087-Serial-Protocol.git

Then install dependencies:

pip install numpy pyserial

Then you're ready to go. So just run the program:

sudo python serialDecoder.py -p /dev/ttyUSB0

If you want a graph as your output, first install GNUPlot:

sudo apt-get install gnuplot

then run:

sudo python serialDecoder.py -p /dev/ttyUSB0 --graph

You also can read from multiple multimeters at the same time and get a CSV output like so:

sudo python serialDecoder.py -p /dev/ttyUSB0 /dev/ttyUSB1

If you only want the actual values and not information about what mode the multimeter is on, use the -q flag:

sudo python serialDecoder.py -p /dev/ttyUSB0 -q

#Protocol Description

	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Byte 1	0	0	0	1	Minus	AC	SEND	AUTO
Byte 2	0	0	1	0	Continuity	Diode	Low Batt	Hold
Byte 3	0	0	1	1	MAX	E4	F4	A4
Byte 4	0	1	0	0	D4	C4	G4	B4
Byte 5	0	1	0	1	DP3	E3	F3	A3
Byte 6	0	1	1	0	D3	C3	G3	B3
Byte 7	0	1	1	1	DP2	E2	F2	A2
Byte 8	1	0	0	0	D2	C2	G2	B2
Byte 9	1	0	0	1	DP1	E1	F1	A1
Byte 10	1	0	1	0	D1	C1	G1	B1
Byte 11	1	0	1	1	Percent	HFE	Rel Delta	MIN
Byte 12	1	1	0	0	u (1e-6)	n (1e-9)	dBm	Seconds
Byte 13	1	1	1	1	Farads	Amps	Volts	m (1e-3)
Byte 14	1	1	1	0	Hz	Ohms	K (1e3)	M (1e6)

All bytes are sent over in hexadecimal numbered one through fourteen. Bytes 3-4 contain digit 4, bytes 5-6 contain digit 3 and so on. All other parts of the display are turned on as shown in the above table.

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serialDecoder.py is a python program to decode the serial output from this DMM. Run:

sudo python serialDecoder.py -p /dev/ttyUSB0

to display a text output of the data. Run:

sudo python serialDecoder.py -p /dev/ttyUSB0 graph

to display a graph of the data.