What I want is using some shell scripts or a custom C software to access the FON1 port and log key presses. My router is a Frtizbox 7360 and using and accorting the device page in wiki FXS seem to be supported.
So in /dev/ there are the following devices:
bus mei_cpe mtd4ro mtdblock5 ttyLTQ0 vmmc17
console mtd0 mtd5 mtdblock6 ubi_ctrl vmmc18
cpu_dma_latency mtd0ro mtd5ro null urandom watchdog
dsl_cpe_api0 mtd1 mtd6 port vmmc10 watchdog0
full mtd1ro mtd6ro ppp vmmc11 zero
gpiochip0 mtd2 mtdblock0 ptmx vmmc12
gptu mtd2ro mtdblock1 pts vmmc13
hwrng mtd3 mtdblock2 random vmmc14
kmsg mtd3ro mtdblock3 shm vmmc15
log mtd4 mtdblock4 tty vmmc16
Which of the one above is the one that FON1 port uses in Frtizbox 7360?
What I want to do is a simpler-to-configure SIP client that directs audio from/to sip into this port.