ELM327P datasheet(26/76 Pages) ELM

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ELM327

ELM327DSH

Elm Electronics – Circuits for the Hobbyist

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WM [1 to 6 bytes]

[ set Wakeup Message to… ]

This command allows the user to override the

default settings for the wakeup messages (sometimes

known as the ‘periodic idle’ messages). Simply provide

the message that you wish to have sent (typically three

header bytes and one to three data bytes), and the

ELM327 will then send them as required, at the rate

determined by the AT SW setting. Note that you do not

have to add a checksum byte to the data – the

ELM327 calculates the value and adds it for you.

[ Warm Start ]

This command causes the ELM327 to perform a

complete reset which is very similar to the AT Z

command, but does not include the power on LED

test. Users may find this a convenient way to quickly

‘start over’ without having the extra delay of the AT Z

command.

If using variable RS232 baud rates (ie AT BRD

commands), it is preferred that you reset the IC using

this command rather than AT Z, as AT WS will not

affect the chosen RS232 baud rate, and AT Z will.

[ reset all ]

This command causes the chip to perform a

complete reset as if power were cycled off and then on

again. All settings are returned to their default values,

and the chip will be put into the idle state, waiting for

characters on the RS232 bus. Any baud rate that was

set with the AT BRD command will be lost, and the

ELM327 will return to the default baud rate setting.

[ display the device description ]

This command displays the device description

string. The default text is ‘OBDII to RS232 Interpreter’.

[ display the device identifier ]

A device identifier string that was recorded with

the @3 command is displayed with the @2 command.

All 12 characters and a terminating carriage return will

be sent in response, if they have been defined. If no

identifier has been set, the @2 command returns an

error response (‘?’). The identifier may be useful for

storing

product

codes,

production

dates,

serial

numbers, or other such codes.

@3 cccccccccccc

[ store the device identifier ]

This command is used to set the device identifier

code. Exactly 12 characters must be sent, and once

written to memory, they can not be changed (ie you

may only use the @3 command one time). The

characters sent must be printable (ascii character

values 00x21 to 0x5F inclusive).

If you are developing software to write device

identifiers, you may be interested in the ELM328 IC, as

it allows multiple writes using the @3 command (but it

can not send OBD messages).

AT Command Descriptions (continued)

ELM327P Datasheet(PDF) 26 Page - ELM Electronics

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