ELM320DSD 查看數據表（PDF） - Elm Electronics

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ELM320DSD

OBD (PWM) to RS232 Interpreter

Elm Electronics 

ELM320

AT Commands

Several parameters within the ELM320 can be

adjusted in order to modify its behaviour. These do not

normally have to be changed before attempting to talk

to the vehicle, but occasionally the user may wish to

customize the settings, for example by turning the

character echo off, adjusting the timeout value, or

changing the header addresses. In order to do this,

internal ‘AT’ commands must be issued.

Those familiar with PC modems will immediately

recognize AT commands as a standard way in which

modems are internally configured. The ELM320 uses

essentially the same method, always watching the

data sent by the PC, looking for messages that begin

with the character ‘A’ followed by the character ‘T’. If

found, the next characters will be interpreted as

internal configuration or ‘AT’ commands, and will be

executed upon receipt of a terminating carriage return

character. The ELM320 will reply with the characters

‘OK’ on the successful completion of a command, so

the user knows that it has been executed.

Some of the following commands allow passing

numbers as arguments in order to set the internal

values. These will always be hexadecimal numbers

which must be provided in pairs. The hexadecimal

conversion chart in the next section may prove useful

if you wish to interpret the values. Also, one should be

aware that for the on/off types of commands, the

second character is a number (1 or 0), the universal

terms for on and off, respectively.

The following is a summary of all of the AT

commands that are recognized by the current version

of the ELM320, sorted alphabetically. Users of

previous versions of this product (v1.x) should note

that their ICs will only support the E, H and Z options.

AR

[ Automatically set the Receive address ]

Responses from the vehicle will be acknowledged

and displayed by the ELM320, if its internally stored

receive address matches the address that the

message is being sent to. With the auto receive

mode in effect, the value used for the receive

address will be chosen based on the current header

bytes, and will automatically be updated whenever

the header bytes are changed.

The value that is used for the receive address is

determined based on the contents of the first header

byte. If it shows that the message uses physical

addressing, the third header byte of the header is

used for the receive address, otherwise (for

functional addressing) the second header byte,

increased in value by 1, will be used. Auto Receive

is turned on by default.

D

[ set all to Defaults ]

This command is used to set the E, H, L, and R

options to their default (or factory) settings, as when

power is first applied. Additionally, the Auto Receive

mode (AR) will be selected, data will be transmitted

in the standard formatted way (as if chosen by FD),

the ‘NO DATA’ timeout will be set to its default value,

and the header bytes will be set to the proper values

for the OBDII operation.

E0 and E1

[ Echo off (0) or on(1) ]

These commands control whether or not characters

received on the RS232 port are retransmitted (or

echoed) back to the host computer. To reduce traffic

on the RS232 bus, users may wish to turn echoing

off by issuing ATE0. The default is E1 (echo on).

FD

[ send Formatted Data ]

This command requests that all responses be

returned as standard ASCII characters which are

readable on virtually any standard terminal program.

Hex digits are shown as two ASCII characters, and

spaces are provided between each byte as a

separator. Also, every line will end with a carriage

return character and (optionally) a linefeed

character, ensuring that every response appears on

a new line. This is the default mode.

H0 and H1

[ Headers off (0) or on(1) ]

These commands control whether or not the header

information is shown in the responses. All OBD

messages have an initial (header) string of three

bytes and a trailing check digit which are normally

not displayed by the ELM320. To see this extra

information, users can turn the headers on by

issuing an ATH1. The default is H0 (headers off).

ELM320DSD

Elm Electronics – Circuits for the Hobbyist

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