I'm trying to do FM modulation on a signal and pass it to the PC and demodulate it using matlab. Matlab requies the frequency deviation in addition to the carrier frequency to do the demodulation. I considered using timer 555, Xr2206 and Icl8038 to do the FM modulation but their data sheets don't show anything about the default frequency deviation or how to set it. How can I find it? and if there is another option to do FM modulation with a known frequency deviation please share it with me. I know that frequency deviation can be calculated by the modulation index, but even that I couldn't find it on the data sheets. Here are the links for the data sheets of the 3 chips.