Specifications

8 of 19ELM323DSD Elm Electronics – Circuits for the Hobbyist
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AT Commands Summary
ELM323 AT Commands
general
set all to DefaultsD
show the ID stringI
reset allZ
repeat last command<CR>
responses
Echo on/offE1/0
Headers on/offH1/0
Linefeeds on/offL1/0
ST hh Set Timeout (hh*4ms)
use Packed DataPD
use Formatted DataFD
requests
SH xx yy zz Set Header
SR hh Set Rx address
MA Monitor All
BD Buffer Dump
AR Auto Receive
SW hh Set Wake (hh*20ms)
SI Slow Init
FI Fast Init
bus control
hexadecimal value from 00 to FF. The maximum
possible time delay of 5.10 seconds thus occurs when
a value of FF (or decimal 255) is used. The default
setting is 7D (or decimal 125) which provides a
nominal delay of 2.5 seconds between messages.
Note that the value 00 (zero) is treated as a very
special case, and must be used with caution. It is used
to stop all periodic messages, by telling the ELM323
internally that the bus is no longer active. This can be
convenient if the vehicle has timed out (perhaps when
using the AT MA command) and you wish to inform
the ELM323 of that without performing a full reset.
Issuing AT SW 00 will not change the previous setting
for the time between wakeup messages.
Attempting to communicate with the vehicle after
issuing AT SW 00 will result in the ELM323 perfoming
a bus initialization sequence.
Z [ reset all ]
This command causes the chip to perform a
complete reset as if power were cycled off and then on
again. All settings are returned to their default values,
and the chip will be put in the idle state, waiting for
characters on the RS232 bus.
Figure 1 shows all of the current ELM323 AT
commands in one convenient chart. In order to help
with the understanding of these, we have grouped the
commands into four functional areas, but this has no
bearing on how they need to be used – it is only for
clarity. You may find this chart to be useful when
experimenting with the IC.
Figure 1. ELM323 Command Summary
ELM323