I'm trying to interface a 5*7 dot matrix display with a controller.As far as i understood,i should use pnp transistors(BC557 for ex.)to multiplex(choose a single column(anode)) and connect the rows (cathodes)to put a value on the selected columns leds.Then,i should choose the next column and so on.This should be done fast enough so that human eye shouldn't observe that leds are shut during this scheme.
Does that(if the above is correct) means i should use timer1 for ex. with compare mode A,and when the suitable time is gathered,the interrupt routine should :
select a column by applying logic 0 to the base of the pnp transistor and put a value on the rows port and repeat this for rest of columns.
How much is that proper time for the eye to catch the changes?What is the "minimum trigger time" of the dot matrix display?
After that proper time passes should i select one column and apply the row values to it,exit the routine then after it passes again,select the next column and so on?Or all columns should be serviced one after the other in the same routine in the same time?