Harware comms buffer to protect SPI
You are asking for non-inverting isolation driver. A unidirectional quad (4 lines) would be enough to buffer all 4 SPI lines.

There are many, many options. Here is one very cool one that offers 1K volt RMS (!) of isolation between the inputs and outputs...

http://www.silabs.com/products/power/isolators/Pages/Si80xx-digital-isolators.aspx

(Read about how it works- there is NO electrical connection between input and output!)

That said, my guess is that this might not be what you need. If you tried an opto-isolator and still had problems, them there might be something else going on. Did the opto-isolator not work at all, or did you still get damaged pins even with it in line?

You might want to try some simpler solutions first. Try maybe a resistor and clamping diode like this...







simulate this circuit &ndash; Schematic created using CircuitLab