ChibiTerm in a dongle

Projects / ChibiTerm  Original post date: 04/24/2016

I found a couple of DB9 to RJ45 break out adapter along time ago in a garbage bin. They seem to be the right size for housing the PCB. These are quite expensive dongles and a few times the cost of ChibiTerm. ;) The cheap grey ones from China is narrower, but the PCB might fit diagonally. I don't like the cheap plastic look however.

The (ABS?) case is very nicely welded together and parts of it is seamless. I don't want to break it into halves for easier access.

Dongle case, PCB and connectors sizing

I cut the plastic at the back with large/small box cutters, hand filed the inside. I filed the access slot on the bottom. I also heated I shaped transformer laminated core to melt the plastic.

I am thinking of making a small PCB with a 4-pin header to sit in the slot and have the wire exit in the bottom opening. Here is how the Serial and PS/2 connectors fits at the back. The pins have to be trimmed to fit in the case. (If I had the RJ45 insert,it would be easier to make a breakout cable)

PS/2 and TTL serial connector

The PS/2 connector is just the right height except for the pins and the extra bits of plastic standoffs at the bottom for wave solder. There is a cover at the back side of the connector that can be slid open.

backside of PS/2 mini-Din connector

The individual stamped contacts are inserted into the housing and the back cover hold them in place. The pins exits at 90 degrees through the cover.

Behind that plastic cover

So looks like I'll need to mod the connector. I might be using fine magnetic wires to solder to the pins inside and breakout to a PCB at the top horizontal slot and solder wires from there. I'll hold off the rest of the mod until my parts arrives from China to assemble more PCB.

Parts from China (ordered on Mar 17) arrived today (May 12). That's close to 2 months now. The Canada Custom still haven't cleared their backlogs. :(

I soldered up a PCB. This one has Crystal, resistor network, resistors, transistor, 3.3V LDO (XC6206P332MR) and ARM chip from China. I program in a working firmware and scoped out the sync and the video signals and it seems to be alive!

Populated module with mods installed.

modding for the serial connector

I make a breakout for the Mini DIN connector with magnetic wires and a small piece of PCB for the breakout to wires. Reassemble the connector before trimming off the leads.

Breakout for the mini-Din connector before trimming off the leads

Mini-Din fitted into case

Soldering everything up. Have to curl the wires so that they fit better. I wired the bootstrap pin to an unused pin on the VGA connector so that I can update the firmware without taking things apart. The connector is snapped into place.

PS/2 and TTL serial port. Power can be fed from the serial port or from PS/2 with a splitter.

Connect PS/2 keyboard, TTL serial and VGA plug to the dongle

Just like the demo video. The serial port is connected to my Dockstar. I have to turn off the AutoLF in my code as Linux uses linefeed for new line.

Size comparison: (Key from an old lock that no longer exists, so don't bother copying the key.)

Dongle vs old house key

The dongle when fitted with a male connector could be plugged directly onto the monitor. (Mock up shown below)

I use my AT keyboard from my old luggable PC and this used monitor from a Thrift shop to make a usable terminal.