CAMERA OPEN XLKpin, PLKpin, HSpin, VSCpin, RETpin, D0pin
This initialises the camera, It outputs a 12MHz clock on XLK (PWM) and checks that it is correctly receiving signals on PLK, VS, and HS.
The camera is set to a resolution of 160x120 (QQVGA) which is the maximum achievable within the limits of the available memory.