environment

visual basic version 6 running under microsoft windows xp operating system was chosen as the target development environment as it gave straightforward access to speech, graphics, serial interfacing and camera interfacing

windows is not a real-time operating system - as it does not support pre-emptive multi-tasking or inter-task synchronisation- but the real time performance is sufficient for the needs of this project

concurrency

the interface executable module and all of the lower level modules that it calls run synchronously with the following exceptions:

• the speech module calls into a microsoft library function which uses a separate process to produce speech asynchronously
  the advantage of this is that processing continues whilst speech is produced
  the disadvantage is that callback functions have to be implemented in the calling module to move the mouth of the simulation during speech
• the seetron dll which takes care of low level communication with the servo motors when using the ssc servo controller uses a separate process to send commands to the servo motors asynchronously
  this reduces the delay in instructing the motors but it has the disadvantage that any position instruction that it is buffering is overwritten if a new instruction is issued before it is cleared from the queue
  the result is that movement is likely to miss intermediate steps on a slow processor
  a full description of how the seetron dll works can be found on the seetron web site (see links)
• the sensor module is called from the interface module on a separate timer
  this means that camera sampling occurs on a timer so it runs concurrently with the control system which is desired behaviour as it is important for the sensor module to continue monitoring the cameras irrespective of what the control system is doing so that the previous image, which is compared to the current image to find motion, does not become too old
  

portability

the system runs on a pc with the following minimum specification:

• 1ghz processor
• 256 mb memory
• 1 usb port
• 1 serial port
• sound card

the periodic aspects of the system are independent of processor speed

integration

the format and scope of the vectors sent from the sensor module to the interface module are as follows:

N	target is in the north sector
NE	target is in the north east sector
E	target is in the east sector
SE	target is in the south east sector
S	target is in the south section
SW	target is in the south west sector
W	target is in the west sector
NW	target is in the north west sector
C	target is in the centre section
F	movement level is above fright threshold
X	movement level is above intrigue threshold
L	left pir sensor triggered
R	right pir sensor triggered
P	front pir sensor triggered
H	microphone level is above noise threshold
Void	movement is below boredom threshold

communication between the modules uses microsoft component object module (com) which is the recommended method for communicating between visual basic 6 components