As you might have noticed, the 38-KHz pulse generator is built around the evergreen timer chip NE555P (IC1). Here, the RC components (R5-C3-P1) set the astable frequency to drive the infrared light ...

I have a Mitsubishi Electric AC MSZ-FT25VGK which comes with a SH20D remote. It seems not to be supported by IRremote8266. I did run IRrecvdumpV2/3 and did a bit of further analysis with ToniA's ...