the plain fact is it is a matrix. in order to control each led without having a separate output for each led it needs to switch from row to row or col to col. in other words scan the matrix. if your seeing hy flash, then it is not scanning fast enough. by adjusting the scan rate and pulse width you can control the brightness. as loannis said it's doing what it's supposed to be doing. with a scope you can actually see the pulses and determine if they are too short or too far apart or anything else that is happening with them. if you just want them all on or off take out the pic and insert a switch.