Please ignore the previous answer which gives information on digital inputs, not digital outputs.
The BL4S200 runs its digital i/o through three Rabbit RIO chips and you do not have direct access to read the state of the output.
There are only two functions, setDigOut which configures it as an output, and DigOut which sets the state of a configurable output. You can read the return code from this second function to see if the state was successfully set:
void digOut(int channel, int state);
Sets the state of a configurable I/O channel configured as a sinking digital output
to a logic 0 or a logic 1. This function will only allow control of pins that are configured
by the setDigOut() function call to be a sinking digital output.
channel digital output channel, 0–31 (DIO0–DIO31).
state set output to one of the following states:
0 — connects the load to GND
1 — puts the output in a high-impedance tristate.
0 — success.
-EINVAL — invalid parameter value.
-EPERM — pin function was not set up as a digital output