I have filed a tech case on this with Cypress, but thought community should know -
If this function is given a non legit DTMF dial character/value, hangs
That would be any ordinal value not belonging to "0123456789,*#AaBbCcDd"
Clearly if noise or any other corruption of a value occured, would be good
if it does not take main() down.
After some testing Cypress and I idid AP'Is seem to be OK, my problem
was another issue. So not sure why your background mode is not working.