All-In-One DB9

Using, learning, programming and modding the Gigatron and anything related.
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kerouanton
Posts: 10
Joined: 27 Jun 2018, 18:40

All-In-One DB9

Post by kerouanton » 18 Sep 2018, 13:38

I like the Gigatron esthetics so much, that I hanged it on my wall! Unfortunately that means if I want to use it, I need to plug at least 4 cables (power, audio, vga and controler), which isn't really nice hanging around.

Image

Since the DB9 connector still has 4 empty pins, and power and H and V sync are already there, the goal is to put all remaining signals on it.
The mod is simple (a few short cables behind the PCB from Line_out and RGB to the DB9) and reversible.

Code: Select all

┌─────────────────────────────────┐┌─────────────────────────────────┐
│          ┌───────┐              ││          ┌───────┐              │
│          │       └─┐            ││          │       └─┐            │
│          │ 5 ■     └─┐          ││  VGA_RED │ 5 ■     └─┐          │
│          │       ■ 9 │          ││          │       ■ 9 │ VGA_BLUE │
│SER_PULSE │ 4 ■       │          ││SER_PULSE │ 4 ■       │          │
│          │       ■ 8 │ GND      ││          │       ■ 8 │ GND      │
│SER_LATCH │ 3 ■       │          ││SER_LATCH │ 3 ■       │          │
│          │       ■ 7 │          ││          │       ■ 7 │ VGA_GREEN│
│ SER_DATA │ 2 ■       │          ││ SER_DATA │ 2 ■       │          │
│          │       ■ 6 │ VCC      ││          │       ■ 6 │ VCC      │
│          │ 1 ■     ┌─┘          ││ LINE_OUT │ 1 ■     ┌─┘          │
│          │       ┌─┘            ││          │       ┌─┘            │
│          └───────┘              ││          └───────┘              │
│  GIGATRON DB9 ORIGINAL          ││  GIGATRON DB9 "ALL IN ONE"      │
└─────────────────────────────────┘└─────────────────────────────────┘
This enables to use a single DB9 extension cable to transmit everything to a small breadboard box including the Arduino Nano, and the VGA, Controler and audio ouputs. That would be neat and clean to get a simple extension box with a single db9 wire to the Gigatron.

Any thoughts?

tocksin
Posts: 16
Joined: 22 Jun 2018, 14:12

Re: All-In-One DB9

Post by tocksin » 18 Sep 2018, 16:05

You could have a one cable that splits out into the multiple connectors. Or have the cables in a cable wrap, so it looks like one cable. Like this:

https://www.parts-express.com/parts-exp ... k--080-558

kerouanton
Posts: 10
Joined: 27 Jun 2018, 18:40

Re: All-In-One DB9

Post by kerouanton » 18 Sep 2018, 18:42

Sure.
This is also a proof of concept for my beginner's building skills. I hope this weekend I'll have this finished. Already soldered the wires on the PCB.

It's really crap compared to all the impressive hacks all of you guys did until now. #mindblown!

User avatar
marcelk
Posts: 178
Joined: 13 May 2018, 08:26

Re: All-In-One DB9

Post by marcelk » 19 Sep 2018, 18:14

kerouanton wrote:
18 Sep 2018, 13:38
Any thoughts?
This is a clever find. Two thoughts:

1. The DB9's +5V line is intended as an output, and that using it as an input by-passes the multi-fuse. You might want to add one on what will now be an input.

2. The pulse lines are slightly different between the jacks because of the 68 ohm resistors, but I see no real problem from a function point of view. These resistors are a bit arbitrary anyway (we copied them from some reference design), and I even can't remember exactly why there are none on the DB9's output (it may even be a mistake, RF emission-wise). Not much thought was put in those lines at all.

kerouanton
Posts: 10
Joined: 27 Jun 2018, 18:40

Re: All-In-One DB9

Post by kerouanton » 20 Sep 2018, 19:54

Thanks for the feedback. Yes the VCC is supposed to be an output and there is no protection. I'll try to see if the usb input on the arduino nano can be used to power the Gigatron.

Meanwhile I've prototyped the thing, except for the arduino and power which still runs on the "official" input.

Image

No display issue, the image is crisp.
The major issue here is audio shielding. There is a loud humming sound on line input, because of the proximity of the video signals running down the same cable. I also have an issue with the joystick input but it's probably a mistake while soldering or cabling.

kerouanton
Posts: 10
Joined: 27 Jun 2018, 18:40

Re: All-In-One DB9

Post by kerouanton » 23 Sep 2018, 18:17

v1 Finalized this weekend.
All fits in a compact box, including the Nano to control from a PC.

Image

TODO:
- When the Nano AND the controler are connected together it causes an issue, as it starts Snake. I'll have to check why. Maybe adding a physical switch to switch off the Nano may help when using the controler.
- Sending the sound through a shielded cable.
- Powering the Gigatron through the Arduino 5V output fails. Probably not enough for the MCP100. I'll check for another way to send the 5V input.

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