I've scoured Google for a solution to this to no avail.
I'm trying to hook up the 1Hz square wave output of a DS3231 RTC breakout board to GPIO18 (pin 12) of the Pi. As per information on the web I've turned on the wave output (theoretically, using an Arduino sketch) and added a resistor between SQW and VCC. "bcm2708.pps_gpio_pin=18" has been added to /boot/cmdline.txt, "pps-gpio" has been added to /etc/modules and /pps0 shows up in /dev. However, when I run "sudo ppstest /dev/pps0" the only output I receive is "time_pps_fetch() error -1 (Connection timed out)".
I suspect I'm missing something very simple or I've got something drastically wrong. Can anyone shove me in the right direction? Thanks.