h.sie's Oxygen-Supply fix question

[CaptBones]

First, let me assure everyone that I really appreciate and enjoy the work that h.sie and the others who helped him, put into his hardcode fixes for SH3.

However, from my experience the Oxygen-Supply fix is not entirely correct and I’m hoping someone (perhaps even h.sie) can provide some help to “fix the fix”.

The idea for the fix and the basic approach are fine, but in the real world there is one significant difference that I have found slightly annoying. Oxygen content monitoring in an enclosed atmosphere is not usually done directly, especially with 1940’s technology; what you monitor is the CO2 content. That’s for two reasons; first because the CO2 content is actually more critical and second because direct detection of the O2 content is not as easy or as accurate as detection of the CO2 content.

Would it be possible to revise the Oxygen-Supply fix such that the LI reports the CO2 level instead of the O2 level? I suspect...and am hoping…that could be done by changing the text and the function that generates that text report, such that 21% O2 equals 0% CO2, 20% O2 equals 1% CO2, and so on, down to 17% O2 equals 4% CO2, at which time the bottled O2 supply is used to “restore” the atmospheric quality. I know that isn’t exactly, technically, chemically correct, but it would be “close enough for government work”.

I started to fix this to my own taste by changing the report given when the boat surfaces and the O2 content is restored to normal. I changed “en.menu” line 4816 to read ”Ventilate the boat.” I also changed line 4817 to read “CO2 level high. Using oxygen supply.” But, when I started to think about tinkering with line 4815, I decided to ask for help first, since I don’t know how the % oxygen is calculated and making a “simple” change to the apparent arithmetic might break the whole thing.

I was also wondering if the optional O2 gauge part of that fix could be retained in the LI’s slide-out gauges, while also keeping the CO2 gauge above the compressed air control manifold in the Control Room functioning as a CO2 gauge (I noticed the face of that gauge still reads “CO2“).

Thoughts anyone…hints, tips…”here’s how to do it” directions?