ELM327LSM datasheet(64/94 Pages) ELM

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ELM327L DSA

Elm Electronics – Circuits for the Hobbyist

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ELM327L

Programming Serial Numbers

Saving a Data Byte

A number of our customers have asked for ways

to uniquely identify a product that uses our ELM327

integrated circuit. While this is often a request for a

means to store a ‘serial number’, people have also

asked for a way to store dates, and version codes, too.

The @2 and @3 commands were created to assist

with this.

If you send the command AT @2 to a new

ELM327 integrated circuit, you will receive an error.

That is, you will see a response that looks like this:

>AT @2

In the above dialog, the ELM327 is trying to tell

you that either the chip is very old and does not

support the @2 command, or that nothing has been

programmed into these memory locations yet.

To program characters into the @2 memory, you

must provide exactly 12 characters using the AT @3

command. These characters must be in the ASCII

printable group, in the range from ‘!’ (hex value 21) to

‘_’ (hex value 5F). Typically, an AT @3 command use

would look like:

>AT @3 MYBOARD_9906

This number can never be altered once it is

entered, so you must be sure that you are entering the

values properly. If developing code which does this,

you may find that purchasing an ELM328 IC will save

the expense of trial and error. The ELM328 does not

support OBD protocols however, so is not a viable

option for other uses.

Once the @3 code is set, it will always be

available through the @2 command:

>AT @2

MYBOARD_9906

That’s all there is to using the ELM327 device

identifier.

The ELM327 provides one memory location that

can be used to save any single byte of information.

This location uses special ‘non-volatile’ EEPROM

memory for storage, so your data is not lost, even if

you should turn the power off.

Typically, this memory location is used by the

controlling software to store the state of flags that were

set by vehicle conditions, by hardware configurations,

or by software choices. By storing them in this type of

memory, the settings will be remembered between

uses of the scan tool.

Storing data is easily done with the Save Data

command - for example, to save the value 7F, simply

send:

>AT SD 7F

and data is just as easily retrieved using the Read

Data command:

>AT RD

Since this single byte of data is stored in the

internal EEPROM array, it is subject to the usual limits

of EEPROM technology - unlimited reads, but typically

only about 1 million writes, with a retention time of 40

years (or more). This should not pose any limits to

ELM327 users that we are aware of.

ELM327LSM Datasheet(PDF) 64 Page - ELM Electronics

ELM327LSM Datasheet(HTML) 64 Page - ELM Electronics

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