5
High Level Description
A hardware reset (by asserting
XRST) should be performed
before starting any operation. It
is assumed that factory
calibration was performed prior
deployment of ADJD-J823.
Calibration is discussed at the
end of this section.
The user controls and configures
the device by programming a set
of internal registers through a
serial interface. At the start of
application, the following register
data must be written to it:
••
••
• Frequency registers
••
••
• Setup data
••
••
• Calibration data
••
••
• Bright and color input registers.
The register data is usually
gathered during a calibration
process which is performed once
in manufacturing. Factory
calibration is needed at a system
level to map the integrated tri-
color sensor’s reading (device
dependent) with a standard
device independent color space.
Once the register data is entered,
the feedback operation begins;
the device starts to sample the
RGB sensor using the internal
ADC. That data is compared to
a user-controlled color point
target. The PWM duty factor for
each channel is adjusted in
response to any error signal
generated by that comparison
operation.
Thus, the actual color produced
by the LEDs is maintained close
to the target.
There are three methods to
operate the device. They are
differentiated by the technique in
which the register data is stored
and used. The three figures
below describe the methods.
NVPROM stands for Non-Volatile
Programmable Read-Only
Memory such as an EEPROM.
DEVICENVPROM
HOST
CONTROLLER
SDASLV
SCLSLV
DEVICE NVPROM
SDAPROM
SCLPROM
HOST
CONTROLLER
SDASLV
SCLSLV
DEVICE NVPROM
SDAPROM
SCLPROM
Dedicated NVPROM in Standalone
Mode
A dedicated NVPROM is
connected to the device.
During factory calibration, the
host can instruct the device to
upload the register data to the
NVPROM. The difference
versus Interactive Mode is
that, in application, the device
itself will download the
register data and immediately
after, enter normal mode.
Then, it will start driving the
PWM channels to achieve a
default target color point. The
default color point is
programmed after factory
calibration. A host controller is
not necessary during
application. The serial
interface protocol between
device and NVPROM is hard
coded. So, a standard NVPROM
such as a serial I2C EEPROM
with address 0x50 (7-bit) must
be used.
Dedicated NVPROM in Interactive
Mode
A dedicated NVPROM is
connected to the device.
During factory calibration, the
host can instruct the device to
upload the register data to the
NVPROM. At the start of
application, the host can
instruct the device to
download the register data
from the NVPROM, after which
the device will wait for further
instructions in normal mode.
The serial interface protocol
between device and NVPROM
is hard coded. A standard
NVPROM such as a serial I2C
EEPROM with address 0x50
(7-bit) must be used.
Independent NVPROM
The NVPROM is independent
from the device. During factory
calibration, the host must read
the register data from the
device and write it to the
NVPROM. At the start of
application, the host must read
the register data from the
NVPROM and write it back to
the device, after which the
device will wait for further
instructions in normal mode.
