ELM327P datasheet(29/51 Pages) ELM

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ELM327

ELM327DSC

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

Setting the Headers (Cont’d)

AT SH command that uses only three hex digits. It

actually operates by simply adding the leading zeroes

for you.

The

bit

CAN

standard

typically

makes

functional requests (ID/header = 7DF), but receives

physical replies (7En). With headers turned on, it is a

simple matter to learn the address of the module that

is replying, then use that information to make physical

requests if desired. For example, if the headers are on,

and you send 01 00, you might see:

>01 00

7E8 06 41 00 BE 3F B8 13 00

The 7E8 shows that ECU#1 was the one

responding. In order to talk directly to that ECU, all you

need do is to set the header to the appropriate value (it

is 7E0 to talk to the 7E8 device – see ISO 15765-4 for

more information). From that point on, you can ‘talk’

directly to the ECU using its physical address, as

shown here:

>AT SH 7E0

>01 05

7E8 03 41 05 46 00 00 00 00

Hopefully this has helped to get you started. As we

often tell those that write – if you are planning to do

some serious experimenting with OBD, you should buy

the relevant standards.

ELM327P Datasheet(PDF) 29 Page - ELM Electronics