Operation Manual

ELM327
69 of 94ELM327DSJ Elm Electronics – Circuits for the Hobbyist
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Programmable Parameters (continued)
rate, or the Carriage Return character, for example,
and forget what you have set them to. The Carriage
Return value that is set by PP 0D is the only character
that is recognized by the ELM327 as ending a
command, so if you change its value, you may not be
able to undo your change. In this case, your only
recourse may be to force all of the PPs off with a
special hardware trick.
When the ELM327 first powers up, it looks for a
jumper between pin 28 (the OBD Tx LED output) and
circuit common (VSS). If a jumper is in place, it will turn
off all of the PPs for you, restoring the IC to the factory
default settings. To use this feature, simply connect a
jumper to circuit common (which appears in numerous
places - pins 8 or 19 of the ELM327, pin 5 of an
RS232 connector, one end of most capacitors, or at
the OBD connector), then hold the other end of the
jumper to pin 28 while turning the power on. When you
see the RS232 Rx LED begin to flash quickly, remove
the jumper – the flashing LED means that it worked
and the PPs are all off.
This feature should only be used when you get
into serious trouble, and it’s your only choice (since
putting a jumper into a live circuit might cause damage
if you put it into the wrong place). Be careful if you
need to use it.
0A Linefeed Character 0A R00 to FF
Programmable Parameter Summary
The following pages provide a list of the currently
available Programmable Parameters. The character
shown in the ‘Type’ column indicates when changes
will take effect. Possible values are:
I - the effect is Immediate,
D - takes effect after Defaults are restored
(AT D, AT Z, AT WS, MCLR or power off/on)
R - takes effect after a Reset
(AT Z, AT WS, MCLR or power off/on)
P - needs a Power off/on type reset
(AT Z, MCLR, or power off/on)
01 Printing of header bytes (AT H default setting) D
02 Allow long messages (AT AL default setting) D
03 NO DATA timeout time (AT ST default setting)
setting = value x 4.096 msec
00 to FF 32
(205 msec)
D
00 Perform an AT MA command after powerup or reset FF
(OFF)
R00 = ON
FF = OFF
FF
(OFF)
FF
(OFF)
00 = ON
FF = OFF
00 = ON
FF = OFF
PP Description Values Default Type
06 OBD Source (Tester) Address. Not used for J1939 protocols. F1 R00 to FF
00 to 02 01 D04 Default Adaptive Timing mode (AT AT setting)
07 ILast Protocol to try during automatic searches 0901 to 0C
09 Character echo (AT E default setting) R00
(ON)
00 = ON
FF = OFF