Right so that's CMOS levels. The PIC pins are CMOS output and TTL input levels. Quite likely, the micros in the WS are the same, or are CMOS in and out. The short version is: CMOS will drive TTL, but TTL will not drive CMOS. This means you should be able to use HC. If you have problems with signal corruption, maybe try HCT... Or, use HCT at first and then try HC when it works. The only problem you'll have is data corruption, nothing should get fried. Here have an interesting link or two http://www.allaboutcircuits.com/vol_4/chpt_3/10.html http://www.interfacebus.com/voltage_threshold.html