elcojacobs:
It would be possible to use ShiftPWM to drive each row. The difference with a matrix and a chain is that in a matrix, you basically alternate in driving multiple chains. The maximum duty cycle for the LED's is 1/rows.
If each time you reset the counter, you also switch rows you can make some modifications to use it for matrices.
Investigating this some more, I think I understand. If I switch the column(using your above example) when the counter reaches 0 then each pwm cycle will happen on a new set of LED's. This would effectively drop the overall refresh rate by the number of columns being used.
Say you were using an 8x10 matrix at pwm speed 50hz. The 8 Rows being driven by the 595's and some other way of selecting the columns(there seem to be mulitple ways of doing this). It would take 10 PWM cycles to complete 1 refresh of the whole matrix. Meaning 5hz for the whole screen. Can your PWM cycle speed be increased high enough to bring the whole matrix up to 50hz? Does this mean straight multiplying the PWM hz by the number of columns, in this case equalling 500hz?
I am sorry if any of the above is incorrect. I am just trying to understand as I would like to use your library. I am trying to see if I could drive a 16x16 RGB matrix this way. ( if above is correct that would need 800hz for the pwm cycle but there would only be 6 SR's being driven)