frequently used for serial and I2C buss
I happen to have this circuit on one
of my favorite Propeller controllers: the
EFX-TEK HC- 8+ (the SIO port). If you don't,
I've also laid out a little breadboard-friendly
module (Figure 3) that you can use for
experimenting with LANC.
The typical LANC port on a
camcorder is a 2. 5 mm stereo jack.
Figure 4 shows the connections on the
controller's stereo plug. I don't use the 5V
from the camera; this voltage goes away
when the camera goes into sleep mode
while the pull-up is maintained. This allows
a "sleeping" camera to be awakened by
pulling the LANC line low for more than
140 ms. Using the circuit in Figure 2, we
can do this via software control.
The LANC jack will be marked as
such; usually with the logo shown in
Figure 5. If you have a Sony camcorder
that uses a 10-pin A/V jack, you'll need to
get an adapter. I prefer to buy my camera
gear from reputable companies like B&H
Photo in New York; their part number for
an adapter is #LIA3AV. If you would rather
shop elsewhere, do a web search on "LANC AV adapter"
and you'll be presented with a lot of choices. What
you're looking for is shown in Figure 6.
From a basic software standpoint, LANC is very
simple: The camcorder sends an eight-byte packet
60 times per second (every 16. 7 ms). LANC bytes are
eight bits, plus a start bit and three stop bits. Yes, three.
Remember, LANC has been around for a long time and
in the early days, micros were not nearly as fast as they
are today. Those extra stop bits gave early micros enough
time to process each byte. What this all boils down to is
that we have about 6. 7 ms between packets. As with
ADVENTURES IN PROPELLER PROGRAMMING
July 2014 13
■ FIGURE 2. LANC interface schematic.
■ FIGURE 3. LANC interface PCB.
■ FIGURE 4. LANC plug.
■ FIGURE 5.
■ FIGURE 6. LANC to AV adapter.