I recorded the wav file from a tape, worked fine with openmsx. But I failed to convert it to .cas file by msxcastools (and others).
Is there any way to convert the file with openmsx?
missumj: You can not do this OpenMSX AFAIK, because there are other utilites for the job, and for most people separate utilites make more sense considering the workflow.
Note that the cassette needs to use the original MSX BIOS encoding (custom loaders will not work, unless they do not change the modulation). It's a limitation of the CAS file format, IIRC (this has been discussed here before) .