ELM624_1 Datasheet, PDF (12/16 Pages) ELM Electronics – Control L (LANC) to RS232 Interpreter

ELM624
Power Control
Beginning with v3.0 of the ELM624, an output
pulse can be generated on the LANC output, simply by
issuing an AT SP command. The ‘pulse’ is actually an
active (low) signal that lasts for 150 milliseconds.
Many LANC devices respond to this pulse, some
by toggling the power on and off each time it is issued,
but most by waking up when they receive it. In order to
use this command, you would typically start the device
you wish to control, and either let it go to sleep by
itself, or issue a power off command (105E, 102A, or
something similar). When the device is in this ‘sleep
state’, it can often be ‘woken‘ simply by issuing a Send
Pulse command (AT SP). Note that not all devices can
be turned off by software commands, and not all will
wake up to this signal, but you may be fortunate and
yours may.
Monitoring from Powerup
The ELM624 IC can be put into a special
continuous monitoring mode at powerup, or during a
software reset (AT Z) without any input being required
from the user. This allows the IC to be used in
translator type projects such as ‘LANC logic probes’,
or simply inputs to computer based controllers.
If the RS232 Rx pin is found to be at an active
(high) level throughout the entire powerup sequence,
the IC will print the ID string (ELM624 v3.0), will set the
output mode to ‘Raw Data’, and will then immediately
go perform a monitor all command. This can be very
useful if all you need to do is to monitor the signals
being sent between other LANC devices. Note that 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.
This monitoring mode will remain in effect until the
Rx input (pin 5) returns to a low level, no matter
whether there are sync signals or not, or even if there
are only sporadic sync signals. Once the Rx does go
low, the ELM624 will perform a ‘soft reset’, restarting
itself into the normal mode of operation. A software
and will be ready for your commands. The Example
Applications section shows an example of how you
might wire a ‘LANC logic probe’.
Error Messages
There are actually very few errors that the
ELM624 can report. There can be errors in the user
input, or there can be problems with the LANC signals:
NO SYNC
There is no recognizable synchronizing signal at the
ELM624’s LANC input. The IC has searched for
some time, attempting to detect a signal that it could
synchronize to, and failed. Check your connections,
and the power to the LANC device, then try again.
SYNC ERROR
A problem has occured while receiving one of the
eight LANC bytes. A synchronizing signal had been
detected, but either that was a false detection, or
something has now happened to the signal. As with
the NO SYNC condition, check your connections,
and the power to the LANC device, then try again.
?
This is the standard response for a misuderstood
command received on the RS232 bus. Usually it is
due to a typing mistake, but occasionally it can be
from problems with the connection to the computer.
ELM624DSD
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