Using devices with specific timing requirements (aka "deterministic timing") on a system with non-deterministic timing IO is always going to be a little bit hit-or-miss.
There are so many variables which can affect the timing on the IO that you'll need to use experimentation and inspection (using a logic analyzer or oscilloscope) to see exactly what is happening at what time on the pins. Then when you have it working you need to acknowledge that the timing may shift due to the nature of the operating system on Galileo. This is not a fault or weakness in Galileo, it is purely a facet of the fact that it's a complex device with an operating system, not a simple micro-controller without one.
There are other ways to connect one-wire devices to Galileo as has been discussed a few times now in these forums. My own recommendation would be to build a small interface between the device and one of the industry standard interfaces already present on Galileo, which are: UART (Serial), I2C, SPI, USB and LAN. Then you can use the operating systems own systems to connect reliably every time to your device.
