Hello jscax,
Are you saying that the YS-IRTM uses the "UPD6121". I thought it used a STC11F02 microcontroller. I am frustrated about finding information on the module I bought - looks like the one in your link to Aliexpress. STC11F02 is an 8051 micro - I will see if I can use STC software to get the embedded firmware, and try to disassemble it.