FIELD OF THE INVENTION
This invention relates to Interface Card for Data Recorder Unit (DRU) of Solid State Flight Data
Recorder (SSFDR) and, more particularly, for the reception of Harvard Bi-Phase Data from Data
Acquisition Unit (DAU) and Interfacing of Audio Module.
BACKGROUND OF THE INVENTION
Flight data recorders are monitoring and recording instruments, carried aboard an aircraft, which
systematically monitor and store the instantaneous values of various aircraft parameters. Early
recorders were analog electromechanical devices which periodically marked, in analog form, the
value of a given airplane parameter on a moving wire or other permanent storage medium. The
time of occurrence of the parameter was also suitably scribed into the medium opposite the
mark for the sensed parameter. Subsequently, digital flight data recorders have been developed
which operate by converting each analog aircraft parameter into a corresponding digital signal,
and storing the digital signals on a permanent storage medium such as magnetic tape.
The numerous mechanical parts employed in the analog and digital type electromechanical
flight data recorders have rendered such units expensive to construct and bulky in design,
requiring periodic maintenance of the mechanical parts. In addition, extraction of the stored data
from these data recorders requires physical removal of the storage medium.
The development of solid state memory devices, such as electrically erasable read-only
memory, has led to the design of all solid state flight data recorders. The solid state flight data
recorders commonly employ a data acquisition system (DAS) which receives and processes the
various aircraft input signals to be monitored and stored under the control of a central
processing unit (CPU). The analog signals are converted to digital signals by the DAS and,
under CPU control, are passed over a data bus to the solid state memory devices.
Programming within the CPU controls the processing of input airplane signals to corresponding
digital signals through the DAS and the subsequent transference of these digital signals to
controlled locations in the solid state memory.
The signals representative of monitored aircraft parameters are typically either discrete level
signals or analog signals. Discrete signals are typically switch positions and produce either a
high or a low level output depending upon the status of the particular switch. A typical example
in an aircraft is a squat switch, which indicates whether or not a load is being borne by the
landing gear.
The Data acquisition unit, the main LRU in the system. It acquires data from cockpit voice,
analog inputs, thermocouples, RTDs, Tacho, discrete inputs, MIL1553B bus & ARINC 429
channels from the aircraft. The acquired data is stored in Flash memory available within the
DAU and the selected parameters are sent to Recorder Unit (RU) through ARINC 717 interface.
The stored parameters in DAU flash memory are milked out through Ethernet 10/100 port.
These parameters are used for post flight & engine run analysis.
SUMMARY OF PRESENT INVENTION
The present invention, therefore, is directed to Interface Card for Data Recorder Unit (DRU) of
Solid State Flight Data Recorder (SSFDR).
An aspect of the present invention is the ability of receiving Harvard Bi-Phase Data of the Data
Acquisition System to process a set of parameter sense signals and recording of digitized data
in memory module.
A further aspect of the invention is to interface with the Audio module for processing and
recording of digitized voice data from audio card. Audio Card connected to Interface card with
Interface connector.
The activities of Interface Card have been scheduled / configured such that it finishes all its
activities in one second which is accomplished by using micro controller internal RISC timer and
keep on repeating the same for ever till the system is ‘ON’. The Interface Card performs
activities like – updating NVRAM contents, performing CBIT, fault indication – if any, data
acquisition from DAU, Audio Acquisition, and FCS data. Then, it makes direct parameter frame,
Audio frame and FCS data frame, stores these frames into Protected Memory Module (PMM),
transmitting the frame on RS422 for telemetry.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention become more apparent and descriptive in
the description when considered together with figures/flow charts presented:
Figure 1: is a Block Diagram of Data Recorder Unit (DRU)
Figure 2: is a Block Diagram of Interface Card
Figure 3: is a Block Diagram of Audio Card Interface
DETAILED DESCRIPTION
The interface card consists of following modules, which are described below:
RS-422:
This is a differential bus transceiver, used for replaying the data stored in Protected Memory
Module (PMM). Here four devices are used. One device is used entirely for transmission, the
other one for reception and rest two are spare channels, which can be configured as both
Transmitter & Receiver for future use. Differential bus transceiver is used for RS422 device.
RS-232:
RS-232 is a multi channel RS-232 Driver/Receivers, used for downloading the application
program onto the Micro-controller. The application program is downloaded using the receiver
(RXD) & Transmitter (TXD) pin of the Micro-controller. This is mainly a level converter, which
converts the TTL level voltage to RS 232 level voltage. The RXD & TXD are the input & output
from the Micro-controller, whereas the RS 232 RX & 232 TX is the input & output from the PC.
Reset Circuit:
The Reset interface of the Micro-controller with MAX device. The micro-controller gets its
power-on or external reset from the supervisory circuit. A provision for external manual reset is
provided through the connector. The RESET output pin of the reset device remains low for
200msec during power ON or when reset externally. Further, the output stays low whenever the
VCC (+5V) supply is below the threshold of 4.65V. The WATCH DOG output also has a RESET
output. In this, WATCH DOG is pulled up by +5V, this is one of the inputs to the PFI (Power
Failure Input) of device and the other input comes from the port pin of the micro-controller.
When PFI goes below +1.25V, PFO (Power Failure Output) goes low, which resets the system.
DRU Fault Indication Circuit
This circuit is used mainly to sense any fault in the system using the DOLL’S eye. DOLL’S eye
is an indicator, which glows whenever a +28 V RTN path is established, which is established
whenever there is any failure in the system by using the following logic. The WATCH DOG,
which is one of the inputs to the PFI of the supervisory circuit along with one of the port pins of
the micro-controller, is pulled up by +5V. Whenever there is any fault in the system, this WATCH
DOG goes low, which puts ON the PNP transistor. The collector of transistor is given to the
opto-coupler, which puts ON the transistor inside, whose one end is connected to two diodes
connected back to back. A voltage of 1.4V is developed across base of another transistor, which
conducts and +28V RTN is established. So the DOLL’S eye glows which indicates the fault.
ARINC 573 Buses:
ARINC 717/573 is an interface standard used to record flight data. This interface is used for
receiving the ARINC 717/573 transmitted data from the processor card. For this purpose a Dual
line receiver is used. This device is a digital line receiver, intended for use with digital system
connected by twisted pair lines. The Response time can be controlled with a external capacitor
to eliminate noise spikes. Twisted pair copper wire of gauge number 22 is used with a 0.01uF
termination. This capacitor helps in the power dissipation reduction. There is a strobe input,
which is connected to the digital port of the queued analog to digital converter (QADC) module
of micro controller through a pull up of +5V .The output is high whenever this strobe is low.
The Inputs to this chip is coming from the DRU, which is the Harvard Biphasic encoded data,
which are taken at the input pins of the chip, from the filter plate. The output of this chip is given
to two different time processing unit (TPU) channels in the micro controller in order to process
for two different rates. These are also pulled up by +5V. Any one of the channels is connected
to the chip at a time using the jumper.
Audio Card Interface:
The block diagram for the audio Interface is shown in Figure: 3. The Audio card is connected to
this card at the 53 pin audio connector. The communication between micro controller and the
audio card takes place using a bi-directional buffer. The buffer transmits in one direction
depending on the T/E pin of the buffer. The T/E pin is the direction pin, depending on which the
direction of transfer is selected. One of the buffer’s T/E pin is permanently grounded which
shows that it is acting as a unidirectional buffer. This is connected to address, as address is also
unidirectional. The other buffer is acting as a bi-directional in which the T/E is connected to R/W
bar pin of the micro controller. This is connected to data bus, as it is bi-directional. There is one
more R/W bar pin coming from the audio card, which is tied to R/W bar of the micro controller.
The EXT_RESET pin of audio connector is connected to the reset supervisory circuit, which is
used for external reset. The DPRAM select pin from the audio connector is connected to the
decoder (4:16). The audio_Tx, Audio_Rx which are audio signals are terminated on the Filter
plate
Memory Module Translation Circuit:
The operating voltage levels of the other TTL gates and PMM are different hence comes the
need for using this translation circuit. The other TTL works at 5V, while the PMM operates at
3.3V. There is a separate power supply of 3.3V provided for PMM, but along with this the PMM
requires that the voltage level of other address, control and data lines should also be of the
order of 3.3V. The PMM translation circuit translates the 5V signals to 3.3V and vice versa. This
module also provides timing sequences to various signals by use of latches. It receives the data
from data bus and converts the data for HIGH logic from +5 V to +3.3 V, by using a bidirectional
transceiver for storage in PMM (Protected Memory Module). It also retrieves the data
from PMM.

WE CLAIMS:-
Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Interface Card is for acquisition & processing the actual sensed values of flight & audio data from a plurality of aircraft sensors at different flight modes of the aircraft flight profile, comprising; Data acquisition means, having signal processing means for providing said signal representations to said flight data recording means, and including signal memory means for storing signals; Arinc 717/573 means for receiving flight data from DAU for recording; Audio Module interface means acquiring & recording of voice data; said memory translator means interfacing of memory from microcontroller for storing the data and voice; RS232/RS422 communication means communication of microcontroller with host computer for user interface.

2. Interface Card of claim 1 wherein card is having ARINC 717/573 interface standard used to record flight data. This interface is used for receiving the ARINC 717/573 transmitted data from the processor card.

3. Interface Card of claim 1 wherein audio interface is to connect audio card and it is connected with 53-pin audio connector. The communication between micro controller and the audio card takes place using a bi-directional buffer.

4. Interface Card of claim 1 wherein memory module translator is used to translate the data between Digital (TTL) signal and memory module from 5V to and 3.3 V and vice versa.

5. Interface Card of claim 1 wherein RS-232 Driver/Receivers is used for downloading the application program onto the Micro-controller.

6. Interface Card of claim 1 wherein RS422 is a differential bus transceiver, used for replaying the data stored in PMM. Here four devices are used. One device is used entirely for transmission, the other one for reception and rest two are spare channels, which can be configured as both Transmitter & Receiver for future use.

7. Interface Card as claimed in any of the proceedings claim a fault circuit is provided for detecting the fault in entire DRU system and once fault is detected it indicates the fault through LED indicator in Aircraft through Doll’s eye. ,TagSPECI:As per Annexure-II