Using a GPS to synch time

Target: ConnectCore 9m-2443

I’ve been asked by my customer to implement time synchronisation using a GPS (Time & PPS) the chip for timing is Trimble Resolution SMT.

The UTC time can easy be read using the serial interface Rx Tx pins. Problem lies with PPS. After some digging seems that current driver implement PPS from the DCD pin which does not exists so a driver using a gpio needs be made, also the LinuxPPS patch seems only available in kernels > 2.6.31 Digi’s current version is 2.6.28.

Before I throw myself in this effort to make this work is there any pointer you could give me. The doc shows how to modify the kernel source but what about adding stuff to it and have it compiled.

Could you suggest some reading material on how I could implement the pps device driver.

I also could not locate the source for openNTP within the environment which should require modification to work with PPS.