ELM634
AT Commands (continued)
Remember that they are not case-sensitive, they can
have spaces or tab characters embedded as you wish,
and that for the on/off type commands, the ‘0’
character is the number zero.
BR
[ display the Baud Rate ]
MA
[ Monitor All ]
This command asks the IC for the LIN baud rate it is
currently operating at. The ELM634 only supports
one baud rate, so this command will always return
with the response ‘9600’.
D
[ set all to Defaults ]
This command resets all of the options to their
default values which were set at the last power-up,
or manual reset command. This usually only affects
the echo and linefeed modes, but if the RS232Rx
pin was at an active level during the last reset, the
IC will immediately enter the Monitor All (AT MA)
mode after this command is issued.
Z
E0
and
E1
[ Echo off(0) or on(1) ]
These commands control whether or not characters
received on the RS232 port are re-transmitted (or
echoed) back to the host computer. To reduce traffic
on the RS232 bus, users may wish to turn echoing
off by issuing AT E0. The default is E1 (echo on).
I
[ Identify yourself ]
Issuing this command causes the chip to identify
itself, by printing the startup product ID string (which
is currently ‘ELM634 v2.0’). Software can use this to
determine exactly which integrated circuit it is talking
to, without resorting to resetting the entire IC.
This command causes the IC to immediately begin
monitoring the LIN bus for messages, displaying all
that it finds. It can be interrupted at any time by
activity on the RS232 receive input.
MR hh
[ Monitor for a Response to hh ]
This is a special version of the AT MA command.
Only identifier/command bytes matching the hex
characters ‘hh’ will be displayed, and all others will be
ignored. This can be useful if trying to track down a
troublesome switch problem, or for triggering another
action on a specific input.
[ reset all ]
This combination causes the chip to perform a
complete reset, as if power was cycled off and then
on again. All settings are returned to their default
values, and if the RS232Rx input is not held at an
active level for the entire reset time, the chip will be
put in the idle state, waiting for characters to arrive
on the RS232 bus. Note that the level at the Rxmode
input is measured again at this time, so the RS232Rx
input may be affected if the level at pin 4 has
changed since the initial power-up.
L0
and
L1
[ Linefeeds off(0) or on(1) ]
The option of transmitting a linefeed character after
each carriage return character is controlled by these
commands. If an AT L1 is issued, linefeed
generation will be turned on, and for AT L0, it will be
off. Users may wish to have this option on if using a
terminal program, but off if using a custom interface
(as the extra characters serve no real purpose in
such a case). The default setting is L1 (linefeed
characters are sent after every carriage return).
ELM634DSB
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