display_matrix(unsigned char *BMP, int delay_refresco, int sustain)
The sustain parameter is the time text will be visible in the matrix.
If you want to do another things with your code while the text is displayed......it's another question...and i think that you can't do that....
Seems that the matrix haven't persistence itself.The canton electronic function does a loop for mantain the send picture.
You could simulate it by using interrupts, or some thing like that , but the refresh will do for sure flickering problems.
I think this can be the reason for the very low price. Even so, we can buy a cheap 15$ arduino uno only to control the matrix, (sending texts from the main arduino via serial) and still get a very good total cost for a 64x16 matrix.
Now i don't need to do this, because my arduino will only display text and some draws and will not do another things, but may be an idea for you.