ELM624
AT Commands (cont’d)
FD
[ send Formatted Data ]
Q0 and Q1
[ Quiet mode off (0) or on (1) ]
This command requests that all responses from the
LANC device be sent as standard ASCII characters
which are readable with virtually any terminal
program. The four status bytes (words 4, 5, 6 and 7)
will be sent as eight hexadecimal digits, with two
ASCII characters representing each byte. There is
insufficient time at 9600 baud to insert spaces to
separate these bytes, so they are simply sent as a
block of eight characters. Every line will end with a
carriage return character and (optionally) a linefeed
character, ensuring that all responses appear on a
new line. This is the default mode.
This is a convenient means to stop the continuous
flow of status messages that occur while you are
experimenting. If quiet mode is selected, the chip will
function normally in all respects, except that the
sending of the LANC status messages will be
stopped. The default setting is Q0, quiet mode off.
RD
[ send Raw Data ]
There may be times when one would like to see all
eight of the LANC words that are in a message
instead of just the four status bytes. There is not
enough time to send sixteen hexadecimal digits, a
carriage return and perhaps a linefeed character
while working with 60Hz systems, however. In order
to send this information, it must be kept in it’s un-
converted or ‘raw’ form.
I
[ Identify yourself ]
Issuing this command causes the chip to identify
itself, by printing the startup product ID string (this is
currently ‘ELM624 v3.0’). Software can use this to
determine exactly which integrated circuit it is talking
to, without resorting to resetting the entire IC.
In the raw data mode, the ELM624 performs no
translation of the received LANC data. It simply
leaves each byte as the raw value which was
received, and resends them to the connected PC
along with a single terminating carriage return
character. No linefeed is sent after the carriage
return, regardless of the AT L0/L1 setting. In the
Raw Data mode then, each eight byte LANC
message will always appear as a nine byte RS232
message.
L0 and L1
[ Linefeeds off (0) or on (1) ]
Many computer terminal programs expect a linefeed
character (hex 0A) to be sent after each carriage
return character (hex 0D). The sending of this
linefeed character is controlled by this option. Users
may find that for general use, leaving linefeeds on is
preferrable, but for some computer controlled
applications, they may not require it (and could find
that it only serves to slow processing down). The
default setting is L1, linefeeds on.
This option will likely find limited use by many users
since many of the received values will represent
unprintable characters on a terminal screen, so will
require special capturing and processing for use. If it
is absolutely necessary to see what the value of the
four command words are, however, this is a means
to do so. Note that the values shown in the raw data
response are the result of actual bus reads, and not
simply a regurgitation of what is in the transmit
buffer. If there are bus conflicts or wiring problems,
the values may differ. By default, this mode is off.
MA
[ Monitor All messages ]
Using this command places the ELM624 into a bus
monitoring mode, in which it displays all messages
as it sees them on the LANC bus. This continues
indefinitely until stopped by activity on the RS232
input. To stop the monitoring, one should send any
single character then wait for the ELM624 to respond
with a prompt character (‘>’). Waiting for the prompt
is necessary as time to respond is unpredictable,
and depends on what the IC was doing when
interrupted. If it were in the middle of printing a line, it
would first complete that line before sending the
prompt character, but if it were simply waiting for
input, it would return immediately. The character
which stops the monitoring will always be discarded,
and will not affect subsequent commands.
R n
[ Repeat commands n times ]
This sets the LANC command repeat value. Although
commands are only sent from the computer to the
ELM624 once, they must be sent to the Control L
device multiple times in order to be recognized. The
repeat value supplied (‘n’) can be any single hex
digit, which allows values in the range from 0 to 15
(hex F). Sending a 0 as the parameter (AT R0) is a
special case, which causes the command bytes to
ELM624DSD
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