Provide a turnkey product design package
Services Electrical Design, Firmware Design, & Mechanical
Industry Corporate Communications
Application Multimedia Switching
Other Integrated Third-Party Remote Controller
Communications (All) sought a device enabling it to add value to the
video teleconferencing systems it provides to customers. This device
would give All a product with its own private branding to be associated
with the sophisticated systems it was integrating. They selected to
build an Audio/Video 1-of-4 Selector Switch. Subsequently, All sought
a company with an existing technology to leverage previous knowledge
and experience to minimize the development effort as well as time
All found a company with a 1-of-4 Switch that could switch mono audio
and was controlled via RS-232 serial communications. However, All
was having a custom IR (infrared) Remote control designed to integrate
the control services of the equipment used in its systems and desired
to have the IR Remote remotely control the A/V switch. Additional
functionality included terminating S-Video or NTSC composite video
on each input and output automatically, switching stereo audio, and
up to four remote IR inputs.
Communications provides high-end teleconferencing systems to national
top 100 companies. This includes the design of the telephony and networking
systems required to integrate various multimedia presentation devices
including document cameras, conferencing cameras as well as PCs.
All was interested in establishing a brand of its own that would integrate
and compliment its systems.
In an effort to add value and reduce cost, All embarked on acquiring
a privately branded OEM product, if it existed. This device would
be instrumental in the technical integration and control of the various
multimedia presentation devices.
All identified a company with a 1-of-4 Switch capable of switching
video and mono audio, controlled via RS-232 communications interface.
At the same time All was having a custom IR Remote Control device
designed and developed to combine the control services of the equipment
that was currently used in their systems. Consequently, All desired
to have the remote also be capable operating the A/V Switch.
Additional functionality included accommodating either S-Video or
NTSC composite video at each input and output automatically, ability
to switch stereo audio, and handle up to four remote IR Detector inputs.
Lastly, All was looking for a custom enclosure with a high-tech quality
look and finish that was comparable to the equipment it sold and installed
at customer sites.
of the VS-4 began in the spring of 1999 after it was determined that
the identified off-the-shelf OEM switch was not easily nor cost effectively
modifiable. A manufacturing cost ceiling was established that drove
the requirement for a high level of integration throughout the various
subsystems while maintaining the degree of functionality being sought.
Couple this with a 60-days-to-prototype schedule and youve got
a challenge at hand.
The starting questions posed were; how do we handle the fact that
either composite video or s-video may be present at any given input?
How does Dynazign accommodate either without user intervention? How
do we minimize the need to perform extensive multiplexing?
First, Dynazign modeled the sheet metal enclosure and all exterior
features such as buttons, power and I/O connectors and indicator lamps.
We in turn used this for both virtual proof of concept and generation
of pre-sale literature via 3-D photo-realistic rendering. After the
enclosure design was approved, we generated the appropriate mechanical
drawings and started architecting the electronics.
Second, we selected an appropriate video decoder capable of terminating
s-video or NTSC, with six individual video input ports and had a complementary
video encoder matched to operate with the decoder. Finally, we needed
a video chipset that was low power since our budget was tight for
a power supply that met both national and international safety standards.
By devising a scheme of using two s-video cross point matrices optimized
for s-video and terminating the NTSC ports directly into the video
decoder, we were able to utilize all six input ports into the video
decoder chip. The cross point matrix, decoder and encoder were each
controlled via I2C interface. Thus, only three lines were required
from the processor for the subsystem communications and control. The
cross point matrix chips were specifically designed to have available
two user-settable bits for driving an audio multiplexed switch and
therefore did not require any additional lines from the processor.
Ultimately, only four lines were required to drive the entire 4-to-1-Selector
audio and video functions. An additional four lines were used to receive
the IR inputs from the remote IR detectors. Level translation was
required to terminate the 12V IR Detector input signal since the detectors
could possibly be in excess of 100 feet from the switch.
The microprocessor utilized was a low cost PIC microprocessor from
Microchip Technologies. The device was capable of capturing real time
IR remote input codes while constantly evaluating video input status
from the decoder via continuous I2C interrogation. The microprocessor
chosen did not have an on-board I2C port and therefore was implemented
in firmware. Due to the processing overhead of the I2C routines running
continuously, a low overhead finite state machine executive was implemented
to guarantee that no asynchronous IR commands would be missed.
utilizing a highly integrated video decoder/encoder chipset from Philips
Semiconductor, the task of managing either mode of input video was
simplified while keeping component count low. In addition, the implied
higher quality s-video signal integrity was maintained in lieu of
simple wired OR mixing of the chrominance and luminance signals. Using
a video cross point matrix and a clickless audio mux specifically
designed for such an application also helped to keep the parts count
to a minimum while simplifying layout requirements.
The PICMicro RISC processor used is among the lowest cost most widely
used in industry today. Firmware development was performed using the
LabICE 2000 Emulator development system. All firmware application
code including all video encoder and decoder initialization code (384
bytes) was stored in the OTP (one-time-programmable) devices.
Power was managed via a combination of a switched inverter (for 5VDC)
and distributed isolated low dropout linear regulation (for +5VDC
analog & digital, +3.3VDC analog & digital, +8VDC video muxes
and +12VDC mains).