ELM327LP datasheet(10/94 Pages) ELM

10 / 94 page

Communicating with the ELM327 (continued)

question mark. These include incomplete messages,

incorrect AT commands, or invalid hexadecimal digit

strings, but are not an indication of whether or not the

message was understood by the vehicle. One must

keep in mind that the ELM327 is a protocol interpreter

that makes no attempt to assess the OBD messages

that you send for validity – it only ensures that

hexadecimal digits were received, combined into

bytes, then sent out the OBD port, and it does not

know if a message sent to the vehicle was in error.

While processing OBD commands, the ELM327

will continually monitor for either an active RTS input,

or an RS232 character received. Either one will

interrupt the IC, quickly returning control to the user,

while possibly aborting any initiation, etc. that was in

progress. After generating a signal to interrupt the

ELM327, software should always wait for either the

prompt character (‘>’ or hex 3E), or a low level on the

Busy output before beginning to send the next

command.

Finally, it should be noted that the ELM327 is not

case-sensitive, so the commands ‘ATZ’, ‘atz’, and

‘AtZ’ are all exactly the same to the ELM327. All

commands may be entered as you prefer, as no one

method is faster or better. The ELM327 also ignores

space characters and all control characters (tab, etc.),

so they can be inserted anywhere in the input if that

improves readability.

One other feature of the ELM327 is the ability to

repeat any command (AT or OBD) when only a single

carriage return character is received. If you have sent

a command (for example, 01 0C to obtain the rpm),

you do not have to resend the entire command in

order to resend the request to the vehicle - simply

send a carriage return character, and the ELM327 will

repeat the command for you. The memory buffer only

remembers one command though, and there is no

provision in the current ELM327 to provide storage for

any more.

10 of 94

ELM327L

ELM327L DSA

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

Please Note:

An issue with the EUSART used in a previous version of the ELM327 resulted in the

possibilty of NULL characters (byte value 00) being inserted into the RS232 data. This

was very rare, but we recommended that software filter for NULL characters and remove

them if found. Although there are no known issues with the ELM327L’s EUSART, we still

recommend that all NULL characters be fitered from data that is received from the

ELM327L.

ELM327LP датащи(PDF) 10 Page - ELM Electronics

ELM327LP датащи(HTML) 10 Page - ELM Electronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94

датащи скачать

ссылки URL