ELM624
Control L to RS232 Interpreter
Description
The Control L or LANC interface is an industry
standard for many audio and video devices. It uses a
bit serial format that is similar to RS232, but differs
enough that devices cannot be directly connected to
one another. The ELM624 provides the necessary
logic to allow almost transparent transfer between
the two systems.
In operation, commands are sent to the ELM624
using an RS232 serial connection, translated to the
Control L format, and sent to the controlled device
on the LANC port. The resulting responses are then
converted to a series of ASCII characters and
transmitted back to the controlling serial device.
This integrated circuit was designed to provide a
cost-effective way for experimenters to work with the
Control L system, so many features typically found in
commercial devices, such as RS232 handshaking,
variable baud rates, extra buffering of signals, etc.
have not been implemented. Responses are kept to
a minimum as well (eg. a single question mark is
returned for a misunderstood command), but the
general principles are demonstrated, and for many
applications, this is all that is required.
Features
• Low power CMOS design
• High speed RS232 communications
• Configurable with standard AT commands
• ASCII output formatted as standard hex digits
• Minimum of external components required
• Most Control L formats supported
• External reset input for system use
• Crystal controlled for signal accuracy
Connection Diagram
PDIP and SOIC
(top view)
V
DD
XT1
XT2
1
2
3
4
8
7
6
5
V
SS
LANC
Tx
Rx
Applications
• Video editors
• Time-lapse recording controllers
• Remote camera controls
• Computer control of A/V equipment
reset
V
DD
Block Diagram
XT1
2
Control L
Interface
V
SS
Master
Oscillator
Control
7
LANC
XT2
3.58MHz
3
V
DD
reset
4
RS232
Interface
6
Tx
Rx
5
ELM624DSB
Elm Electronics – Circuits for the Hobbyist
1 of 7
ELM [ ELM ELECTRONICS ]
