ELM329LP datasheet(13/87 Pages) ELM

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ELM329L

ELM329L DSA

Elm Electronics – Circuits for the Hobbyist

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AT Command Descriptions

<CR>

[ repeat the last command ]

Sending a single carriage return character causes

the ELM329 to repeat the last command that it

performed. This is typically used when you wish to

obtain updates to a value at the fastest possible rate -

for example, if you send 01 0C to obtain the engine

rpm, you need only send a carriage return character

each time you wish to receive an update.

Do not use ‘AT’ before this command.

. [1 - 8 bytes]

[ send bytes with the 11 bit ID ]

If your currently active protocol uses a 29 bit ID,

there may be times when you would like to send a

single message that has an 11 bit ID. This command is

used for that.

A single period (‘.’) followed by 1 to 8 data bytes

will cause the ELM329 to send those data bytes along

with the currently defined 11 bit ID. The data will be

sent exactly as provided - no formatting bytes or filler

bytes will be added, and the number of data bytes sent

will be the same as what you provide (so if you need to

send 8 bytes as for ISO 15765, then you must provide

all 8 of them). The default value used for the 11 bit ID

is 7DF, but this may be changed with the AT SH xyz

command. See the ‘Mixed ID (11 and 29 bit) Sending’

section for more information.

A protocol must be active before you can use this

command, as the ELM329 needs to know the current

baud rate, etc., but it does not have to be a 29 bit one.

That is, you may use this ‘dot’ command with an 11 bit

ID protocol, for example, if you needed to send

unformatted data along with ISO 15765 formatted data

(but the current firmware only allows you to define one

11 bit ID/header).

Do not use ‘AT’ before this command.

: [1 - 8 bytes]

[ send bytes with the 29 bit ID ]

If your currently active protocol uses an 11 bit ID,

there may be times when you would like to send a

single message that has a 29 bit ID. This command is

used for that.

A single colon (‘:’) followed by 1 to 8 data bytes

will cause the ELM329 to send those data bytes along

with the currently defined 29 bit ID. The data will be

sent exactly as provided - no formatting bytes or filler

bytes will be added, and the number of data bytes sent

will be the same as what you provide (so if you need to

send 8 bytes as for ISO 15765, then you must provide

all 8 of them). The default value used for the 29 bit ID

is 18 DB 33 F1, but this may be changed with the

AT SH xxyyzz or AT SH wwxxyyzz commands. See

the ‘Mixed ID (11 and 29 bit) Sending’ section for more

information.

A protocol must be active before you can use this

command, as the ELM329 needs to know the current

baud rate, etc., but it does not have to be an 11 bit

one. That is, you may use this ‘colon’ command with a

29 bit ID protocol, for example, if you needed to send

unformatted data along with ISO 15765 formatted data

(but the current firmware only allows you to define one

29 bit ID/header).

Do not use ‘AT’ before this command.

AT0, AT1 and AT2

[ Adaptive Timing control ]

After an OBD request has been sent, the ELM329

waits to see if any responses are coming from the

vehicle. The maximum time that it waits is set by the

AT ST hh setting, but this setting is purposely a little

longer than it needs to be, in order to ensure that the

IC will work with a wide variety of vehicles. Although

the setting is adjustable, many people do not have the

equipment or experience that it would take to

determine an optimal value.

The Adaptive Timing feature automatically sets the

timeout value for you, to a value that is based on the

actual response times that your vehicle is responding

in. As conditions such as bus loading, etc. change, the

algorithm learns from them, and makes appropriate

adjustments. Note that it always uses your AT ST hh

setting as the maximum setting, and will never choose

one which is longer.

There are three adaptive timing settings that are

available for use. By default, Adaptive Timing option 1

(AT1) is enabled, and is the recommended setting.

AT0 is used to disable Adaptive timing (so the timeout

The following describes each AT Command that the

current version of the ELM329 supports, in a little more

detail. Many of these commands are also described

further in other sections:

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