The radio receiver is normally equiped with a 25kHz synchronous communication board.You can see a photograph of it right here. The manufacturers part number of this board is 791200-1.
The synchronous communication is done by DS8820A and DS8830 IC's.
The DS7830 is a dual differential line driver that also performs the dual four-input NAND or dual four-input AND function. TTL (Transistor-Transistor-Logic) multiple emitter inputs allow this line driver to interface with standard TTL systems. The differential outputs are balanced and are designed to drive long lengths of coaxial cable, strip line, or twisted pair transmission lines with characteristic impedances of 50Ohm to 500Ohm. The differential feature of the output eliminates troublesome ground-loop errors normally associated with single-wire transmissions.
The DS8820A is a digital line receiver with two completely independent units fabricated on a single silicon chip. Intended for use with digital systems connected by twisted pair lines, they have a differential input designed to reject large common mode signals while responding to small differential signals. The output is directly compatible with TTL or LS integrated circuits.
08-09-2006
Making of : preparing the 40 DIL on the ABC miniboard
Here we are preparing the ABC mini board on a 40 DIL socket.
07-09-2006
Making of 2 : preparing the photo-sensitive epoxy PCB
Ready for take off. Here we are ready to fire some 300W UV ray's onto a photo-sensitive epoxy PCB.
06-09-2006
Making of 3 : Peter etching the PCB
Just counting the minutes for etching the PCB, in the kitchen.... Wife standing by in background, wondering whether husband is beyond salvation ...
05-09-2006
Making of 4 : placing the components
Finally starting the real work.
04-09-2006
Making of 5 : finally done
The complete PCB. Only find that last component.
03-09-2006
You Tube 1 : 25kHz signals
Here you can find some animation of the protocol signals of the WJ8888 radio receiver. The signals from the receiver are displayed on a Dynatec Oscilloscope 8120 (2x20MHz). The first channel is the 25kHz clock signal received from the WJ8888 and the second channel is the 64 bit wide dataword send from the WJ8888. Triggering was done on the first channel. http://nl.youtube.com/watch?v=oyzgFfv6JnQ
Hopefull we get some more animations online soon.
05-08-2006
Screenshot 1 : PC software interface
Here you can see a screenshot of the PC software interface running under Windows XP. All important buttons and indications are grouped in one screen. Down at the screen you can find a LCD which displays all radio receiver settings in text format. Above the LCD you have the tuning resolution group. Please notice the additional resolutions 100kHz, 1MHz and 10MHz. At the right of the resolution group you find the selectors for IF bandwidth, gain mode and detection mode. There is also a keypad tuning feature for direct tuning. Settings for the RS232 protocol is also integrated into the main screen. At last there is a bit display which indicates binary patterns of the protocol data send to the receiver.
04-08-2006
Screenshot 2 : Start up screen
Start up screen
03-08-2006
Screenshot 3 : LCD Mini Monitor Mode
LCD Mini Monitor Mode pop up screen
02-08-2006
Screenshot 4 : Maxi Monitor Mode
Maxi Monitor Mode
01-08-2006
Screenshot 5 : TTL square wave analyzer
Here you can see a TTL square wave analyzer. This analyzer gives in realtime the status of the databits send to the receiver. The analyzer is included as a popup so you can call it as an overlay. Each databit in the protocol is graphical shown with low and high signals giving a 64 bit wide wave.
31-07-2006
System overview
This schematic gives an overview how the system works:
30-07-2006
Optocoupler interface
The interface is designed with optocouplers for optimal electrical insulation between receiver and PC.
29-07-2006
Microcontroller
We used an ABC mini board with 40 DIL package. The heart of this circuit is an Atmel AT90S8535. There are 32 user configurable I/O available giving us plenty of IO to do the job. Each I/O pin is software definable as input or output. On the board there is also a MAX232 IC mounted so we can communicate with RS232 protocol. On the ABC mini board there is also an in circuit programming connector so we can program the microprocessor without disconnecting the board out of the circuit giving us more flexibility during debugging and maintenance.
28-07-2006
LCD
A 16x2 LCD screen is used for information about the internal signals of the microprocessor. You can follow in real time the information on the LCD. Also the LCD can dump additional information such as: radio settings, binary patterns, CRC checks, etc. In combination with the software TTL square wave analyzer this gives a lot of information about the actual status of the protocol. A special data led output is also available which gives the status of the databits send to the receiver.
27-07-2006
MIL Connector
The project was put down for a while because we searched hard to find the correct MIL connector. The part number of the MIL connector is JTG06RE12-22P(SR). Please notice that the photograph does not represent the correct connector, although it is used to give an idea of a MIL connector. The Amphenol company is one of the largest manufacturer of military connectors. A large amount of documentation you can find on the website at http://www.amphenol.co.uk/.
25-07-2006
Testing
Debugging and testing the software was done using a STK500 development board. For testing purpose we did use Atmega8535 and Atmega16 microprocessors running at 8Mhz. This means that the microprocessor executes 8.000.000 instructions per second. Prior of debugging the software was simulated using the BASCOM internal simulator.
The WJ8888 can be equipped with two different communication boards. One type is the asynchronous, while the other type is the synchronous board. Please notice that these boards were optionally installed, so it is not sure you have a board installed at all. The only way to know for sure is to open the WJ8888 and have a look at the internal slots. The manufacturers part number is 791200-1 for synchronous IO, and 791201 for asynchronous IO.
Our software is designed for two platforms, so both asynchronously and synchronously protocols. Due to lack of an asynchronous board we could not test the asynchronously version fully, although we have tested it on two computers, one simulating being the WJ8888.
If you have installed an asynchronous board, you don't need the special interface and you can run directly the WJ8888 by RS232 protocol.
On the other hand, when installed a synchronous board, the interface is needed to have the system working. The PC software always converts the setting on the screen into a asynchronous datatable. Only when the synchronously mode is selected the software calls a special mathematical function to convert the asynchronous table into a synchronous table. This is done because place and amount of bits are different in both modes. Once the synchronous table is converted, additional header, command and CRC checksum characters are added. This table is then send asynchronously, still including start, stop and parity bits, to the internal UART buffer of the microprocessor. The microprocessor scans on unique header characters in the datastream, and once found them, the microprocessor accepts the datapackage as being valid data. When data is validated, the microprocessor starts stripping start, stop and parity bits from the received table. After stripping, the databits are stored into an array which can be addressed by x, y parameters, where x is a byte counter and y a bit counter. After filling the array, the microprocessor start a command call to the radio receiver. Once the receiver have received this command call, it switches into remote mode and starts giving back clock pulses to the microprocessor clock input. The microprocessor read this clock pin and once received a clock signal it sends out a databit selected from the array. After the databit is send on the dataline, the internal x and y counters are incremented and the microprocessor waits for the next clock pulse from the WJ8888. This is done for a total of 64 clock cycles for a full command call. After 64 clock cycles the microprocessor resets the command call giving the WJ8888 the command to shift the received data into the internal memory register, thus updating the segment display and the lamp indicators on the buttons. After one command call the receiver settings are the same to the settings of the PC. Each command call longs for about 2.56 milliseconds. After this the PC and receiver can handle a new command. A new command call is triggered by two different ways. One way is done using a keeping alive signal which triggers every 1350 milliseconds. Another way is to check the actual data settings with the data of the prior command cycle. If both datatables difference, a new command call is triggered. Combination of both trigger signals giving us a stable and fast refresh rate of the WJ8888.
Examples where synchronous datacommunication is used, includes keyboards, aviation black boxes, etc...
Debugging and testing the software was done using a STK500 development board. For testing purpose we did use Atmega8535 and Atmega16 microprocessors running at 8Mhz. This means that the microprocessor executes 8.000.000 instructions per second. Prior of debugging the software was simulated using the BASCOM internal simulator.
The WJ8888 can be equipped with two different communication boards. One type is the asynchronous, while the other type is the synchronous board. Please notice that these boards were optionally installed, so it is not sure you have a board installed at all. The only way to know for sure is to open the WJ8888 and have a look at the internal slots.
