Adding a permanent console port Why do this? Disclaimer Instructions Step 0: Determine if you can even have a console port Step 1: Choose a port type and location Step 2: Source your components Step 3: Build the circuit Step 4: TEST the circuit Step 5: Install the port Step 6: Rejoice! Pictures and source files Source files

 

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Adding a permanent console port

 

Why do this?

 

If you plan to do any kind of reflashing or development work on your MG-350HD, you're going to brick it at some point. If you don't want to open the box every time to plug in an RS232 level converter cable, you might want to add a permanent console port. This page describes one way that someone might do this.

 

Disclaimer

 

This procedure certainly voids whatever warranty might be left over from reflashing the system in the first place. If you are the least bit concerned about touching a soldering iron, don't do this. If you're the sort of person who can make TVs flicker, computers crash, or coffee pots emit purple elephants just by walking into a room, don't do this. In fact, nobody should ever do this at all, it could bring about the end of the universe.

 

Instructions

 

Step 0: Determine if you can even have a console port

 

If your unit has a hard drive, then there may well be no room for a permanent console port such as is described here. You might still be able to do something nasty, like having a cable permanently dangling out of a hole in the back of the unit with the interface board attached -- or something similarly nasty. It's your choice, but having a 3.5" hard drive may well preclude having a permanent console port.

 

Step 1: Choose a port type and location

 

This build description uses a male DB9 connector, such as is often seen on the back of a PC, or other forms of serial-enabled hardware. If you like, you can use one of the many other exciting connectors available, such as RJ45, DB25, VHDCI, or even 3 pieces of wet string misted constantly by a trained monkey to lower the resistance. This is your choice. This page describes a DB9.

 

This page describes putting the connector through the little vent just above the power connector. This is relatively easy to open up and, for a DB9, provides adequate clearance for screws to hold it in place through the mostly-solid plastic of the case. Feel free to put your port somewhere else if you like, but bear in mind any necessary clearances, as well as access to components/connectors below.

 

Step 2: Source your components

 

You will need, at a minimum:

 

• 1 x Maxim MAX3232 chip of some variety. The easiest to work with will likely be the MAX3232CPE, which is a normal 16-pin DIP package. A MAX3232E variety will work fine as well, they just have extra ESD (electro static discharge) protection built in so they're harder to zap by being careless.
• 1 x 16-pin DIP socket for the above chip. You solder this onto the circuit board, and then the chip presses into the holder. This means you don't have to solder directly to the chip, killing it with the mighty heat of your soldering iron. You can also swap it easily with a replacement later in case you somehow zap it.
• 5 x 0.1uF capacitors (that's five of zero-point-one micro farads). It doesn't matter what kind, and whether they're polarised or not, but using unpolarised disc capacitors is easier because you don't have to worry about which way round they go. If you don't have, or can't get, 0.1uF capacitors, you can use higher values (stay below 0.5uF though) -- but keep all the capacitors the same. Low-voltage (50V or less) caps are what you want.
• 1 x LED. Choose your type here, but don't go crazy with high-output LEDs; just stick to one of the boring red, yellow, or green ones you find in the bottom of your parts drawer.
• 2 x 10-way (2x5) IDC connectors and about 15cm 10-way ribbon cable (you can use a variety of other connectors here -- working out what you have and what you can make fit is left as an exercise for the more adventurous reader)
• 1 x 10-way PCB mount pin header
• 1 x 3-way PCB mount pin header and matching plug
• 1 x DB9 male connector -- the plainest you can find is probably easiest.
• hook-up wire

 

This parts list does not include all the hardware you'll need to assemble the circuit, like soldering irons, solder, third hand grippy thing with magnifying glass, integrated lighting and sippy straw, beer, desoldering wick for undoing mistakes, and so on.

 

You can happily build this circuit on a breadboard to test it, and then transfer that to a piece of stripboard, veroboard, or whatever kind of pre-printed prototyping board you can get from your local electronics shop.

 

If you're *really* keen, you might be able to use the files linked below to create your own custom PCB.

 

Step 3: Build the circuit

 

This page is not a tutorial on soldering. There are many good ones out there, and this search might help you find them.

 

Step 4: TEST the circuit

 

Before you wire this in permanently, make sure you can connect your interface board to the MG-350HD header marked J2, and connect the DB9 to your PC, start your comms program (hyperterminal, minicom, etc) set to 38400 8N1, boot the MG-350HD and watch the messages scroll by. If you get it all connected up, boot the MG-350HD, and don't see anything, it's time for troubleshooting.

 

Some things to check:

 

• are the serial port pins you've connected to on the DB9 correct? Look inside the connector with a bright light, and you'll likely see little numbers moulded into the plastic. These are the pin numbers. If they're not there, look on the back of the connector. Make sure you have connected pins 2, 3, and 5.
• Are the DB9 pins connected to the correct pins on the MAX3232? Trace the pin connections back through the 3-way connector. The connections should be:
  • Pjn 5 on the DB9 goes to pin 15 on the chip (or one of the other "GND" connections)
  • Pin 3 on the DB9 goes to pin 13 on the chip
  • Pin 2 on the DB9 goes to pin 14 on the chip
• Are the pins on the MG-350HD header marked J2 connected to the correct pins on the interface board?
• Are you seeing flickering of the LED when you boot up the MG-350HD? Note this will happen almost instantly, and won't go on for more than about 1/2 a second, so watch closely.
• Are you really using the correct serial port on your computer?
• Are you using the correct bit rate, parity, stop bits, etc? It has to be 38400, 8-N-1
• You can also connect an LED directly across pins 1 and 3 on the J2 header for sanity checking; it'll flicker when you boot the MG, as described above. It's only 3.3V, and pretty safe to do.

 

Once you've got your interface working properly, it's time to install the thing.

 

Step 5: Install the port

 

This is where there's no turning back.

 

Chop an appropriately sized hole in the case of your MG-350HD, using a variety of sharp instruments. Be careful not to cut yourself, your pets, your housemates, your LCD monitor, or anything else inside the MG-350HD.

 

Put the DB9 connector through the hole.

 

Mark and make holes for little screws to hold the DB9 connector in place. A soldering iron tip works fine for this, at the expense of being really stinky and probably horribly toxic.

 

Connect the board to the MG-350HD, connect the DB9 to the board, and run another test to make sure nothing got borked while you were installing it.

 

Then you might want to pop some double-sided foam sticky tape on the back of the board and stick it somewhere appropriate to keep it from rattling around.

 

Close the box up.

 

Step 6: Rejoice!

 

Marvel at your handiwork! Consume beer, and regale mere mortals with your tales of mighty struggle, heartbreaking near-defeat, and final crushing victory!

 

Pictures and source files

 

 

Here's a shot of the DB9 connector emerging from the rear of the MG-350HD. Note the slight bending necessary to get it through the vent hole. The right-hand side of the vent fins were not completely cut away -- this provides enough material for the right-hand screw to hold on to.

 

 

A view of the guts of the box. Note that the circuit shown here is built on a protoboard, instead of using the PCB layout represented below. The serial port wires are also soldered directly to the board, and the 12-pin header with the 6-pin plug is a result of cobbling the thing together out of spare parts. It's not pretty, but it works.

 

 

The circuit schematic was created with kicad under KDE on Linux. I don't know if the format is compatible with anything else, but the source file is available.

 

 

The PCB layout was created with pcbnew under KDE on linux, part of the kicad package. GERBER files are pretty much standard as far as I can tell.

 

Source files

 

You can grab the kicad source files here: MG-350HD_console.tar.gz (including the GERBER files for creating the PCB).