Mary,
there is no pattern that I know of, I saw it on pinterest and just winged it ... but it's VERY easy.
I used a jelly roll that was 2.5 inches wide.
for one block you do this:
cut out two dark squares (2.5 x 2.5) and one light square that is 2.5 x 2.5
sew them in a row (light in the middle, with a dark on each side)
then cut 2 strips (about 6 inches long) of the dark and sew across the top and bottom. (your light square is now surrounded by dark fabric).
then cut 2 strips (about 6 inches long) of light fabric and sew on both sides (left and right)
then cut 2 strips (about 10 inches long) of light fabric and sew on the top and bottom
Voila you have one block done.
Do the same thing reversing the light and dark fabric.
Square them up, cut in half (triangles), and sew the opposite triangles together.
You can make all kinds of patterns with these - it's all in how you lay them out!
Good luck!