ELM327P datasheet(39/51 Pages) ELM

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ELM327DSC

Elm Electronics – Circuits for the Hobbyist

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ELM327

The following is a summary of the currently implemented Programmable Parameters (ELM327 v1.2):

Programmable Parameters (Cont’d)

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 hardware trick.

When the ELM327 first powers up, it looks for a

jumper from pin 28 (the OBD Tx LED) to circuit

common (VDD). 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, then hold the other end of the

jumper to pin 28 while turning the power on. As soon

as you see the RS232 Rx LED begin to flash quickly,

you can remove the jumper – the PPs are off. This

feature should only be used when you get into trouble

too deeply, and it’s your only choice (since putting

jumpers into a live circuit might cause damage if you

put it into the wrong place). As well, it is only available

beginning with version 1.2 of the IC, and should not be

used on any previous versions.

OBD Source (Tester) Address. Not used for J1939 protocols.

Last Protocol to try during automatic searches

Description

Values

Default

Type

Printing of header bytes (AT H default setting)

Allow long messages (AT AL default setting)

NO DATA timeout time (AT ST default setting)

setting = value x 4.096 msec

00 to FF

(205 msec)

Character echo (AT E default setting)

Linefeed Character

Perform AT MA after powerup or reset

(OFF)

(ON)

00 = ON

FF = OFF

00 to FF

01 to 0C

00 to FF

(OFF)

00 to 02

Default Adaptive Timing mode (AT AT setting)

RS232 baud rate divisor when pin 6=1

The baud rate (in kbps) is given by 4000/(this value)

For example, to obtain 500kbps, use a setting of 08 (4000/8 = 500)

(Continued on the next page)

(38.4)

08 to FF

00 = ON

FF = OFF

00 = ON

FF = OFF

00 = ON

FF = OFF

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