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plipbox: Hardware

  1. Arduino (2009) and Nano

The firmware was implemented on a prototype build with an Arduino 2009 board and an ATmega328 running at 16 MHz. The final (production) version of plipbox was build with an Arduino Nano v3 board.

You can build either version but I suggest to favor the Nano version as it is more compact. Instead of an original Arduino board you can also use one of the many Arduino clones if the ROM size is sufficient (32K here), the AVR chip matches and enough I/O pins are available. Also a new Arduino Uno is a working alternative to the 2009 version .

Setting up the missing parts for your plipbox isn't that hard: All you need is to by some extra components and wire them together.

1.1 Network with ENC28J60 Chip

The essential addition to your Arduino board is a network shield or network expansion card. Please note, that you need a network card with a ENC28J60 chip from Microchip. Cards using a WizNet chip will NOT work! (e.g. The Arduino Ethernet Shield)

I used the ENC28J60 Ethernet Module from iteadstudio for the Arduino 2009 prototype. The plibpox nano version uses an Ethernet Shield for Arduino Nano UNO purchased on ebay.

Please note: If you use an Ethernet shield then make sure that the shield does not require pins that are already used for the Amiga cable (see below). E.g. the ENC28J60 Ethernet Shield from iteadstudio will not work as it uses some DIGITAL pins for extra functions like an SD card.

The wiring of the Ethernet module is as follows:

    ENC28J60 Ethernet Module     Function           Arduino
    ------------------------     -----------------  ----------------- 
      GND                         GND               GND
      SS                          Slave Select      DIGITAL 10 (PB2)
      MOSI                        Slave In Data     DIGITAL 11 (PB3)
      MISO                        Slave Out Data    DIGITAL 12 (PB4)
      SCK                         SPI Clock         DIGITAL 13 (PB5)
      VCC                         +3.3V Supply      (see Note)

Note: The Ethernet module needs a 3.3V supply while your Arduino 2009 needs to run on +5V. Although the Arduiono already provides a +3.3V power source on a pin, it will be too weak to feed the Ethernet chip. I opted to use a 5V to 3.3V regulator to supply the ethernet module. You can use a ready-made 3.3V regulator board if you don't want to build it yourself. See for example at Sparkfun. The plipbox nano version does need no extra power converter. It is already shipped with the Ethener Nano shield.

1.2 Amiga Parallel Port Cable or Adapter

You need to build a cable from the Amiga Parallel Port (DB 25 male) to the Arduino. Try to use only a short wire length otherwise signal quality will suffer. Up to 10 cm are suitable lengths.

The plipbox nano uses a slightly different pin out compared to the original Arduino 2009 prototype. This change was necessary as the nano shield uses DIGITAL 2 as (unused) IRQ line from the ENC28J60 chip. Therefore the /STROBE signal was moved to PD3 and SELECT there moved o PB1. /STROBE needs PD3 as the firmware tracks external INTs for this signal.

   Amiga Parallel Port         Function          Arduino          Nano
   -------------------         ----------------  ---------------  ---------------
      17 ... 22                GND               GND Pin          <- same
      1                        /STROBE           DIGITAL 2 (PD2)  DIGITAL 3 (PD3)
      13                       SELECT            DIGITAL 3 (PD3)  DIGITAL 9 (PB1)
      11                       BUSY              DIGITAL 4 (PD4)  <- same
      12                       POUT              DIGITAL 5 (PD5)  <- same
      8                        DATA 6            DIGITAL 6 (PD6)  <- same
      9                        DATA 7            DIGITAL 7 (PD7)  <- same
      10                       /ACK              DIGITAL 8 (PB0)  <- same
      2 ... 7                  DATA 0 ... 5      ANALOG 0 ... 5   <- same
                                                 (PC0 ... PC5)

plipbox nano Adapter Board

For the plipbox nano it is advisable to build a small base circuit board with a parallel port connector directly soldered and two pin headers for the Ethernet Nano shield. So you can create a very compact design that fits directly in the parallel port of your Amiga.

I already ship a schematic and layout for a single layer PCB that provides such a base board:

1.3 Serial Port for Terminal Access

The plipbox device can be configured and debugged via the serial console available on all Arduino devices. Usually you don't need extra HW to access this serial port.

A virtual serial port is often available via the USB connection.

Alternatively, you can connect your plip box serial port directly to your Amiga and then use an Amiga terminal program to control the device. In this case you need to connect the TxD, RxD and GND wires from your Arduino to a RS232 level converter and then to your Amiga. The level converter is essential, as the Amiga uses +/-12V signals and the Arduino 0/5V. NEVER connect your Amiga directly!

  1. AVR-NET-IO Board

The german online shop Pollin offers with the AVR Net IO a low cost ATmega32 board (either as a kit for 20 EUR or already assembled for around 30 EUR) that is suitable for the plipbox project. It already contains the ENC 28j60 ethernet controller chip and a DB 25 connector that is already suitable to connect the Amiga. The only thing missing in this setup for plibox is a small wire!

2.1 Add Strobe Wire

You need to add a wire from Pin 1 of the DB 25 Connector (J5) to Pin 16 on the ATmega (IC5):

    DB25 / J5 Pin 1 <-------------> ATmega32 / Pin 16 (PD2) 

If its difficult for you to find the ATmega pin then you can also use Pin 1 of the EXT connector:

    DB25 / J5 Pin 1 <-------------> EXT Conenctor / Pin 1

2.2 Modify Power-Supply (optional!)

If you build the board yourself you might want to replace the 9V power supply required with a 5V regulated power supply (e.g. USB charger). In this Forum Thread you find a picture with the required adjustments for this mod:

  • Remove D1, D4
  • Replace D2, D5 with a wire
  • Remove IC1 and connect pin 1 and 3 of IC1 with a wire

Then you can use a +5V regulated power supply on J1. Please watch the polarity now:

(-) Minus is next to the ethernet connector

That's it! All you need to construct your own plipbox HW is ready!