Book of Sigmarion II: Chapter 8 Preparing for Serial to USB modding

Continuing with yesterday's work, as my first step towards the new serial to USB mod on Sigmarion II, I went to buy a cheap serial (R232) to USB cable (HKD$35, about USD$4.5) and a USB mini B connector (HKD$5, ~USD$0.65).  

The serial to USB cable is very basic in terms of build quality, with the connectors wrapped in cheap rubber like soft plastic, which is actually good for easy removal. 

It took a minute or so to cut open the plastic casing and retrieve the content inside. It is a surprisingly simple small setup. On the serial end, 5 pins and 4 pins are soldered on each side respectively.

The 4 USB pins are clearly labeled on the board as well. 

Plugging the cable into my Win10 PC, a device named "USB-SERIAL CH340 (COM8)" was shown in the device manager. The manufacturer is "wch.cn". The full name is www.winchiphead.com. The chipset is "T340C" (not the common PL2303). The driver is CH341S64.sys (version 3.5.2019.1, built on 30/1/19, surprisingly recent). Setup information is oem12.inf. The device supports hot plug and play. The USB is 2.0 standard.

The board of this cable is so small that it would fit inside Sigmarion II without issue. And space won't be a problem either for replacing Sig2's original serial port with a mini B connector. However, at this moment I am not so sure if the board of this cable is capable of converting the original serial port on Sigmarion II to USB. 

On to the manufacturer's website...

The company's website is hosting quite a bit of useful reference documents. Of particular importance is the techinical handbook http://www.wch.cn/downloads/file/79.html, and the PCB schematic http://www.wch.cn/download/CH340PCB_ZIP.html .

It would be perfect if I can also see the PCB schematic of the serial port on Sigmarion II (which would be VERY difficult to come by).

I have never done this kind of in-depth study of electronics before. Perhaps this is a perfect opportunity for me to obtain some hands-on knowledge and skills.

To be continued.