ELM327
AT Command Summary (continued)
CAN Specific Commands (continued)
J1939 CAN Specific Commands (protocols A to C)
D0, D1
display of the DLC off*, or on
DM1
JE
monitor for DM1 messages
use J1939 Elm data format*
FC SM h
FC SH hhh
Flow Control, Set the Mode to h
FC, Set the Header to hhh
JHF0, JHF1 Header Formatting off, or on*
FC SH hhhhhhhh Set the Header to hhhhhhhh
FC SD [1 - 5 bytes] FC, Set Data to [...]
JS
use J1939 SAE data format
set Timer Multiplier to 1*
set Timer Multiplier to 5
Monitor for PGN 0hhhh
JTM1
JTM5
MP hhhh
PB xx yy
RTR
Protocol B options and baud rate
send an RTR message
V0, V1
use of Variable DLC off*, or on
MP hhhh n “ “ and get n messages
MP hhhhhh Monitor for PGN hhhhhh
MP hhhhhh n
“
“ and get n messages
AT Command Descriptions
The following describes each AT Command that the
current version of the ELM327 supports:
<CR>
[ repeat the last command ]
you wish to write your own logic based on OBD
activity. The counter will not increment past 0xFF as
internal logic stops it there.
Sending a single carriage return character causes
the ELM327 to repeat the last command that it
performed. This is typically used when you wish to
obtain updates to a value at the fastest possible rate -
for example, you may send 01 0C to obtain the engine
rpm, then send only a carriage return character each
time you wish to receive an update.
AMT hh
[ set the Act Mon Timeout to hh ]
When the Activity Monitor Count (ie time) exceeds
a certain threshold, the ELM327 decides that there is
no OBD activity. It might then give an ACT ALERT
message or switch to Low Power operation, depending
on how the bits of PP 0F are set. The threshold setting
is determined by either PP 0F bit 4, or by an AT AMT
value, should you provide it. The actual time to alarm
will be (hh+1) x 0.65536 seconds.
AL
[ Allow Long messages ]
The standard OBDII protocols restrict the number
of data bytes in a message to seven, which the
ELM327 normally does as well (for both send and
receive). If AL is selected, the ELM327 will allow long
sends (eight data bytes) and long receives (unlimited
in number). The default is AL off (and NL selected).
AR
[ Automatically set the Receive address ]
Responses from the vehicle will be acknowledged
AMC
[ display Activity Monitor Count ]
and displayed by the ELM327, if the 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 Activity Monitor uses a counter to determine
just how active the ELM327's OBD inputs are. Every
time that activity is detected, this counter is reset,
while if there is no activity, the count goes up (every
0.655 seconds). This count then represents the time
since activity was detected, and may be useful, should
ELM327DSI
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
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