Logic Analyzers are your friend...

Just wanted to post about how handy a logic analyzer can be.  Last Saturday spent several hours trying to debug why the SPI output to a HT1632 LED controller was working on my Arduino but couldn't get it working with my PIC.  After spending a few minutes with the logic analzyer and decoding the bits coming up from the PC that were true SPI, I then connected it to the Arduino and noticed the output there was NOT SPI per the LED documentation but just simple bit banging.  This also identified my ouput was noisey and not correctly switching the bits states to low.  After sorting out the output settings on the PIC and switching the port to the correct output mode, I can now finally communicate with the LED controller.  Definitely recommend the USB SX module... good price and great features (including 1wire, SPI and I2C decoding.)