ELM327
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.
the PPs are off.
This feature should only be used when you get
into serious trouble, and it’s your only choice (since
putting jumpers into a live circuit might cause damage
if you put it into the wrong place). Be careful if you
need to use it.
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
defaults. 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
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,
R - takes effect after a Reset
(AT Z, AT WS, MCLR or power off/on)
D - takes effect after Defaults are restored
(AT D, AT Z, AT WS, MCLR or power off/on)
P - needs a Power off/on type reset
(AT Z, MCLR, or power off/on)
PP
Description
Values
Default
Type
00
Perform an AT MA command after powerup or reset
00 = ON
FF = OFF
FF
R
(OFF)
01
02
Printing of header bytes (AT H default setting)
Allow long messages (AT AL default setting)
00 = ON
FF = OFF
FF
D
D
(OFF)
00 = ON
FF = OFF
FF
(OFF)
03
NO DATA timeout time (AT ST default setting)
setting = value x 4.096 msec
00 to FF
32
D
(205 msec)
ELM327DSI
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