On Thu, 05 Jul 2001 02:47:07 GMT, "Tim Haynes" wrote: >Hey gang, > >I have a IIgs that is currently using Appletalk over a >Localtalk connection (actually phoneNet connectors that I >scrounged up). One of my phoneNet connectors is kinda weird - >it has a 9pin serial connection (perfect for a Windows COM >port) that is plugged into an adapter to bring it back to the >Mac printer port (geez, I'm out of the loop! What are those >connectors called again? DIN? DB9? Grrr... memory fading...). The Mac connector is RS-422, the PC is RS-232. However, this does not mean a connection is impossible. The actual network is merely two wires run in parallel from machine to machine, in a "Bus" architecture. That fat little box contains a transformer and a bunch of noise filtering components to interface the bus with the serial in/out ports. The main difference between the cheaper Phonenet and expensive Appletalk boxes is what is known as "termination". The ends of the network need to have a resistor connecting the signal to ground. The resistor dampens noise and signal reflections in the wire. Appletalk is self-terminating. By default both ports on an unused box are already terminated. The network cable, when inserted into the box, physically presses back on a switch, and the switch disconnects the terminating resistor for that port. Pull out the cable, and the resistor reconnects. Very slick. Probably why Apple always charged $75 and up for that seemingly useless little box. Phonenet requires manual termination. You have to stick a little phone plug into the spare port, and the plug is wired with a resistor. Now, it WILL work without termination, but likely only with short runs between 2-6 machines in the same room. If you plan to span the network 1000 feet or so, termination is very important. And would ya know it, I've got a disassembled Appletalk dongle right here. Wiring looks like this inside: T1 BUS Wire 1 --+------+--- ----------+--------- Serial Red | | ) ## ( | Term R2 | ) ## ( `--- R4 -- Serial Blu | | ) ## ( Term Sw | ) ## ( | | ) ## ( BUS Wire 2---+----- | -- ## --- N/C | ) ## ( | ) ## ( R1 ) ## ( | ) ## ( .--- R3 -- Serial Wht | ) ## ( | BUS Ground----------+--- ----------+--------- Serial Grn | | `-----------+-- R5 --+-------- Serial GND | | `-- C1 --' (noise filter) Okay, I don't know what the serial wire colors represent but it seems fairly easy to figure out. The main thing you need to know about RS422 is that you might say the sending line has its own ground, and so does the receiving line. It's usually represented as RX+ RX- and TX+ TX- In order for you to send a signal you have to send from RX+ through the transformer and out to RX-. Similarly to receive a signal the transformer must connect to TX+ and TX-. What they have done is tie BOTH signal lines together. So basically the input is automatically receiving whatever is output to the network. I would not be suprised to see that R3 is dampening RX+ and R4 is dampening RX- to keep it from being overloaded by the local signal transmissions on that same machine. Conversion to a PC serial is a problem since the power in the serial port typically flows like this: Sending from PC1 to PC2 Sending from PC2 to PC1 TX -->>>-- RX TX ------- RX PC1 PC2 PC1 PC2 GND --<<<-- GND GND -->>>-- GND RX ------- TX RX --<<<-- TX Ground is multidirectional, balancing the current flow of the various signal lines traveling in either direction. One option is the following. With this, Serial TX flows to local ground, completing the circuit. Meanwhile when a network signal is received, power flows from ground to Serial RX, keeping the polarity the same: T1 BUS Wire 1 --+------+--- ----------+--------- Serial TX | | ) ## ( | Term-R2 | ) ## ( `--- R4 -- N/C | | ) ## ( Switch | ) ## ( | | ) ## ( BUS Wire 2---+----- | -- ## -------------------- GND | ) ## ( | ) ## ( R1 ) ## ( | ) ## ( .--- R3 -- N/C | ) ## ( | BUS Shield----------+--- ----------+--------- Serial RX | | `----------+-- R5 --+------ Serial Shield | | `-- C1 --' (noise filter) I don't really know if this would work. Can you think of any better possible wiring schemes? ------------------------------------------------------------- PHONE-NET box: Hey, wouldn't ya know it, I got one of those too. :) .-- R3 -- Ser Org T1 | BUS 1 -----+-------------- -------+-------- Ser Brn | ) ## ( | ) ## ( | ) ## ( BUS 2 ---- | ---------+--- -------+-------- Ser Red | | | +---. +---. `-- R4 -- Ser Blk Filter | | | | Filter for R1 C1 R2 C2 for BUS 1 | | | | BUS 2 | | | | `---+------+---+------------------ Ser Shield Hmmm, looks a little familiar. Same transformer layout. Only real difference is the filtering. I would have to guess that the extra filtering is needed because these cables are not shielded at all, being plain phone cord. On another front, I have found that Phonenet and Appletalk are so similar that you can just wire the two together without any harm. Take an Appletalk BUS cable and hack it off. Take a phonenet cord and hack it off. Connect the two outer wires of the phonenet cord and attach them to the bus cable wires. Tape it together, and plug it in. -Mr. Boffo mister_boffo@hotmail.com (Mister Boffo) writes: >And would ya know it, I've got a disassembled Appletalk dongle >right here. Wiring looks like this inside: > T1 >BUS Wire 1 --+------+--- ----------+--------- Serial Red > | | ) ## ( | > Term R2 | ) ## ( `--- R4 -- Serial Blu > | | ) ## ( > Term Sw | ) ## ( > | | ) ## ( >BUS Wire 2---+----- | -- ## --- N/C > | ) ## ( > | ) ## ( > R1 ) ## ( > | ) ## ( .--- R3 -- Serial Wht > | ) ## ( | >BUS Ground----------+--- ----------+--------- Serial Grn > | > | > `-----------+-- R5 --+-------- Serial GND > | | > `-- C1 --' > (noise filter) >Okay, I don't know what the serial wire colors represent but >it seems fairly easy to figure out. The main thing you need to >know about RS422 is that you might say the sending line has >its own ground, and so does the receiving line. It's usually >represented as RX+ RX- and TX+ TX- And here are the serial connections from page A-4 of "Inside Appletalk" Second Edition: Wire Sig MiniDIN-8 DE-9 ------------------------------------- Red TxD- pin 3 pin 5 Blu RxD- pin 5 pin 9 Wht RxD+ pin 8 pin 8 Grn TxD+ pin 6 pin 4 GND Case Shield Shield >In order for you to send a signal you have to send from RX+ >through the transformer and out to RX-. Similarly to receive >a signal the transformer must connect to TX+ and TX-. The +/- signals are differential. When TxD+ is +3volts the TxD- will be -3volts giving 6 volts between them. When the signal changes from logical 1 to logical zero the polarities of both lines change. -- David Wilson School of IT & CS, Uni of Wollongong, Australia