Each panel has the following PINs:

OE, GND, A, B, CLK, LAT, DR

OE is output enable, and it is active HIGH, meaning when the OE pin goes high, the LED panels are illuminated. This pin can be fed a PWM signal to adjust the brightness of the display, but it would have to be carefully timed to prevent ghosting. More on this later. 

Pins A & B select the row that is to be displayed. Given (2) bits, A & B pins, there are a combination of 4 different values that can be given to these panels. This is a tip off that the mode of these panels are 1/4 scan. Since each panel is 32 pixels wide by 16 pixels tall, this makes for a total of 512 LEDs per panel. 512 divided by 4 rows equals 128. This indicates we'll need to shift in data in 4 segments, each time shifting out 128 bits. Since there is only (1) DR pin for data, we know we'll be shifting out 4 rows (128 bits divided by 32 pixels) at at time. 

CLK is self explanatory. When the CLK pin goes high, the bit that is present on the DR pin gets shifted into the register. This means we'll have to change the state of the DR pin prior to the CLK pulse. 

LAT is the latch pin.

DR is the data that gets shifted into the registers on CLK high signal, and it is active LOW, meaning when the data is shifted in, the corresponding bit lights up the corresponding LED when the DR pin is LOW. This is a bit backwards from what I'm used to (active high on HUB 75 panels) but not a major issue. 

The driving sequence then for each panel is as follows: (initial startup with OE pin high and LAT low) 

1. Shift in 128 bits of data using the DR & CLK pins
2. Bring the OE pin low to turn off the display
3. Set the LAT pin high, enabling it to allow the data to reach the output pins
4. Select the row you want to display by manipulating the A & B pins
5. Bring the LAT pin low to close the latch
6. Set the OE pin high to turn the display back on

My initial thinking is that I can use shared pins between the panels. For instance, tie all the CLK, LAT, OE, A, & B pins together. My only concern with this is signal capacitance on the lines and the fan out capability on the MCU, which I won't worry about for the moment. I'll just move forward until something goes wrong, then assess the problems. 

Given this, the entire display of (16) panels may theoretically be ran off of 6 pins, not including GND. I will, however, be using 13 pins for this setup which I will explain at a later time, when I discuss the driving method.