Can I add an additional servo controller to the svp-1284? I know I can use 11 I/O lines to create an additional 8 (3 for control) for a total of 16 servo ports. Could I instead use the 8 existing servo ports and control a 16+ channel servo controller using 4+ I/O lines for a total of 24+ servo ports?
You only need a single I/O line to control a serial servo controller, though four would give you TX, RX, ERR, and RST for complete control of a controller like our Mini Maestros. A chain of Maestros can even be connected to the same line, so you can potentially control hundreds of servos.
I recommend using PD0 and PD1 with the built-in UART of the 1284. You can use the serial port functions in our AVR Library to make this relatively easy.
The ATmega1284 has two built-in UARTs, so you could alternatively use PD2 and PD3.