[Ronja] Seeking a Mentor

Tue Jan 22 05:31:24 GMT 2008

Hi David,

  See if this is what u're looking  for
http://ronja.twibright.com/technotes/how.php

  Plus heres some explanation i found in a report by
  CHANCEY, MARK ALAN. Short Range Underwater Optical Communication Links.

  The original document is in pdf, so sorry if the block diagrams are missing.

  UTP – The UTP (Universal Twisted Pair) is the main interface to the PC. The signal from
  the RJ-45 port goes into the RJ-45 Filter. The schematic below shows the pin layout of the
  RJ-45 filter. This filter isolates the board from outside noise. The RJ-45 standard calls for
  twisted pair wires consisting of a positive and negative wire for the transmit and receive, for
  a total of 4 wires. This differential output setup is used to reduce any noise the Ethernet
  cable may receive from outside sources. The positive and negative transmit signal are on
  pins 9 and 11 of the filter. The respective receiver pins are 14 and 16. This can be seen in
  the schematic below. The signal is then passed into the transmitter circuit of the UTP.

  TX Circuit– The transmitter establishes the handshaking between the idle signal and the data
  stream in preparation to be sent to the LED transmission board.
  - MC3486 (Quad Differential Line Receiver) – This IC multiplexes the two differential
  transmission signals (positive and negative) into one signal.
  - 74HC74N (Dual D-Type Flip-Flop w/ Set and Reset) – This IC provides a 1MHz idle
  signal for the LED. This signal is for maintaining a defined DC level and to prevent
  receiver noise and unwanted signals from being amplified in the limiter on the receiver
  board. The system would not work without the 1MHz signal. Packets would be randomly
  lost due to received packet echoes from the opposite direction on shorter links, sometimes
  even on longer links due to random noise resembling a preamble, and most importantly,
  the remaining packet would not be received at all because the corrupted preamble would
  be received by the RJ-45 interface.
  - 74HC14N (Hex Inverting Schmitt Trigger) and 74HC132N (Quad Schmitt Trigger
  NAND Gate) – These ICs work together to decide if the idle signal or data signal should
  be passed. If no packet is detected, the idle signal is passed. When a data signal is
  detected, the idle signal is dropped. The red indicator LED on the board is flashed to
  indicate transmission activity.

  RX Circuit - This circuit filters out the 1MHz signal, passes the data signal to a demultiplexer,
  passes the (positive and negative) signals to the RJ-45 filter which then passes
  them to their respective receive wires on the RJ-45 port.
  - 74HC74N (Dual D-Type Flip-Flop w/ Set and Reset) – Produces Ethernet standard
  250Hz (NLP or Normal Link Pulse) signal which tells the PC the UTP is an Ethernet
  compatible device. Every 4ms this NLP is sent to the PC maintaining the compatibility
  status.
  - Common Emitter Pair – Pre-amplifier for incoming ~700mVpp to ~4Vpp. This
  increases the current and voltage so that incoming pulse train will trigger the input of the
  74HC14N.
  - 74HC14N (Hex Inverting Schmitt Trigger) and 74HC132N (Quad Schmitt Trigger
  NAND Gate) – Rejects the 1MHz idle signal so that it is not passed to the PC. If a data
  signal is detected it passes the signal, otherwise the 250Hz NLP is sent to the PC for the
  reasons described above. The green indicator LED on the board flashes to indicate
  reception activity.
  - MC3487 (Quad Differential Line Driver) – This IC de-multiplexes the incoming data
  signal into separate differential output (positive and negative) receive signals for the RJ-
  45 filter and port.
  Transmitter
  Figure 5-18 Functional block diagram of the transmitter board, Right) The transmitter circuit. Full
  circuit diagram in Appendix B.

  The signal arrives via the coaxial connection. The DC filter removes any DC offset, which
  leaves a pure square wave. Before the signal is transmitted, the signal must be current
  amplified to push the LED. This is accomplished by an emitter coupled transistor pair
  (preamp) and by stacking three 74HC04 ICs. The signal is then ready for transmission via
  the cyan LED.
  Receiver
  Figure 5-19 Functional block diagram of the receiver board, Right) The receiver circuit. Full circuit
  diagram in Appendix B
  The receiver detects the photons via the photo detector. The low current signal triggers a
  dual gate transistor (NTE415) which takes the current from the 12V rail and transmits it to
  the NE592 video amplifier. The NE592 cleans the incoming rounded signal to a square
  wave. Pin 7 of the NE592 is part of a differential output which is used to measure the signal
  strength based on the alignment of the optical signal. This is called the received signal
  strength indicator (RSSI). Pin 8 of the NE592 is the other part of the differential output and
  carries the data stream through a pre-amp/limiter circuit consisting of a pair of common
  emitter connected transistors which limits the signal to ~700mVpp. The signal is then sent to
  the receiving end of the UTP.

  Hope this helps,

  Saad

  Hello.

I am a student at a school in the United States and I'm trying to build the 
Ronja Inferno by myself. I'm breaking up the project into parts and I am 
currently working on the Twister2 Module. I have two boards fabricated and 
am working on soldering parts.

I am wondering if there is anyone on this list that would be willing to give 
some guidance in what I'm doing because at my school I don't have many 
resources.

As a side question, would anyone be able to direct me to a resource that 
explains how the data goes from simple computer data packets and then to 
light and then back to computer data packets?

Thank you,
-David

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