first, let me say that I am NOT using LEDs, these displays are "Pinlights" my drive scheme:
.23 column rails from 5 bit to a BCD decoder.
..Split this into 2 groups 10 + 9
..each of the two groups will be driven by 4 bits to a BCD to 7 seven segment drivers
I also need 4 x 16 segments, as well as this, will require 16 bits of I/O I might use an I/O expander?
I could put all of this on a TI I2C port expanders. The decoders will be driven via 5 bits on the Mega itself.
The KW-104s are 4vdc @ 15ma per segment.
I have more hardware knowledge of hardware + I write software in C, I was originally going to use 2 MAX parts but they use Charlieplexing and therefore will not work in this application. Can you refer me to a sample for the software ( I have seen the shifters but this is not desirable.)
To handle the drive requirements on each of the drive columns there is a BJT connected to the Vcc rail, the column select (base) and one side of the Pinlights common pin.
To finish the segment drives I need a BJT connected to Ground, the segment select (base), and the other side to the Pinlights.
Or a total of 24 cols, 16 + 7 + 7 = 54 BJTs!
refresh rate = .25/23 = 0.010869565 ~ .01 sec or a minimum refresh rate of 100 Hz. much better at 150 - 200 Hz,
by the way, I am also tossing in a dimming circuit using PWM driving a TriState Buffer, enable line that three if you are keeping track.