Book of Sigmarion II: Chapter 9 New USB cap STL, RS232 schematics, new plan for USB client port mod

A new 3D design (v1.0b) is now available on Thingiverse. The "USB" word is replaced by the USB symbol (which I find even cooler!): https://www.thingiverse.com/thing:4645949

The actual make fresh from the printer!

Today the resourceful Mr. stingraze responded to my yesterday's blog post by providing an invaluable link to an old Japanse page that contains the pin assignment of the serial cable (N001M) for Sigmarion II:  

That wiring pattern is for modding for a modem (RJ-45) connection. But for typical simple serial connections such as direct data transfer, according to the official schematic of the simple version of CH340 board (the one I bought), only three pins suffice, namely RxD (pin 2), TxD (pin 3), and GND (pin 5), the remaining six pins being unused.

If that's true, then rewiring Sig2's serial port to CH340 would be relatively easy, despite the super tiny pins to be soldered on. One thing I have to bear in mind is that the pin assignment diagram is for the cable, which means on the Sigmarion II's serial port the assignment is the reverse pattern, i.e. cable's Pin 9 = Sig2's Pin 1, cable's Pin 1 = Sig2's Pin 9, and so on.

Connecting the CH340 board to a USB mini B is a straightforward soldering job.

The next step is to open up my Sig2 again and take a good closer look at the serial connector. A battle plan is now taking shape in the Champion's mind now ...

The CH340 board is now separated for implantation.

The serial connector is a proprietary make (marked with "A2 01X"). 

Probably I don't have to remove this connector as I can simply solder directly to the pins here at the back of the serial connector. 

I just saw the tiny numbers (1 and 9, right under "HONDA JAPAN" ) engraved on the serial connector. Looking at the pins this way, Pin 1 is actually to the left and Pin 9 the right.

My plan is quite simple. 

Step 1: Solder the right pins between Sig2's serial port and the CH340 board.

Step 2: Solder the color wires to the USB min B connector.

Step 3: Piggyback the CH340 board onto the chip right behind the serial connector. There is just enough space for this tiny board to be housed here. Insulation should be added to the bottom of the CH340 board of course.

Step 4: Remove the phone connector to the right of the serial connector. Replace the phone connector with the USB mini B. A small adjustment of the casing may be needed, which can be easily done.

 

If this plan is on the right track, I will implement it in a couple of days.

To be continued.