Actually, you could do it with just 2 instructions per update (using 18F and 40-MHz clock) but it would require a blanking interval of sorts at end-of-period or at some other point in time to update/refresh duty cycle values. In this particular case it would actually be easier to implement with BAM or MIBAM compared to the more traditional PWM methods.
As a side note. I think I have a method for using MIBAM modulation on that little 20-LED charlieplexed array. The refresh rate works out to a whopping 520-Hz per LED which would allow you to fade each individual LED from black to full to black (511 steps) in less than a second. The 520-Hz per LED (or per column) rate is achieved by using a 1.5-usec step or an overall refresh rate of 2600-Hz (with a 1920-usec frame rate). Man I'm good (LOL). Seriously though, this model or method suggests that we could achieve a very respectable refresh rate even with a standard mux'd 8x8 matrix.
Mike
Bookmarks