In SX Microcontrollers, SX/B Compiler and SX-Key Tool, aemileski wrote:

Might want to look at [url=http://forums.parallax.com/forums/default.aspx?f=21&m=282223&g=305679#m305679]my post about the Sure DP-033 6432 LED matrix[/url].

Summary:  For 256 levels you need to latch 256 different ON / OFF states for a single LED in the same amount of time.  Note that the data rate must be 256 times higher, which can be hard to do via bit-banging in software.

A refresh routine something like this might work (pseudo C):

[code]
for (row = 0; row < ROWS; row++) {
    for (b = 0; b < 256; b++) {
        for (column = 0; column < COLUMNS; column++) {
            if B > brightness level of LED[row][column] {
                Shift out data for OFF
            } else {
                Shift out data for ON
            }
        }
        Latch row data
        Turn on LED power for Row
        Delay until next brightness period
    }
    Turn off LED power for Row
    Delay until next row period
}
[/code]

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