ELM320
AT Commands (continued)
are 61 6A F1, as required by the SAE J1979
Diagnostic Test Modes (OBDII) standard.
SR hh
[Set the Receive address to hh ]
Depending on the application, users may wish to
manually set the address to which the ELM320 will
respond. Issuing this command will turn off the AR
mode, and force the IC to only accept responses
addressed to hh. Use caution with this setting, as
depending on what you set it to, you may end up
accepting (acknowledging with an IFR) a message
that was actually meant for another module.
ELM320 AT Commands
general
D set all to Defaults
I show the ID string
Z reset all
ST hh
[ Set Timeout to hh ]
<CR> repeat last command
After sending a request, the ELM320 waits a preset
time before declaring that there was no response
from the vehicle (the ‘NO DATA’ response).
Depending on the application (and priority of the
request), users may want modify this timeout period
before declaring the request a failure. The ST
command is used to do that.
responses
E1/0 Echo on/off
H1/0 Headers on/off
L1/0 Linefeeds on/off
R1/0 Responses on/off
PD use Packed Data
FD use Formatted Data
ST hh Set Timeout (hh*4ms)
The actual time used is (approximately) 4 ms x the
byte value passed as the hexadecimal argument.
Passing a value of FF thus results in a maximum
time of about 1020 ms. Values less than 08 will be
ignored and forced to a value of 8, providing a
minimum time of 32ms. The default value is 32
(decimal 50) providing a timeout of 200 ms.
requests
SH xx yy zz Set Header
SR hh Set Rx address
AR Auto Receive
MA Monitor All
MR hh Monitor for Rxer hh
MT hh Monitor for Txer hh
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. ELM320 AT Commands
AT Command Summary
Figure 1 (at the right) shows all of the ELM320
commands in one convenient chart. In order to help
with the understanding of these, we have grouped
the commands into three functional areas, but this
has no bearing on how the commands are to be
used, it is only for clarity. You may find this chart to
be useful when experimenting with the IC.
ELM320DSC
Elm Electronics – Circuits for the Hobbyist
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