82066163-7050-ab49-b8cc-b3855e8d2252

This extension unit is used for Logitech's RightLight Technology, employed by most Logitech webcams (including the QuickCam E3500). It uses software based multi-field measurements to manage auto-exposure settings on-the-fly. The technology works as follows:

 * The image on the cam will be split into eight fields, each split into left and
 *  -----------------  right halves. To get the light intensity of one field, the
 *  |   |   |   |   |  host should SET the address of the field and then GET the
 *  |  c4   |  c5   |  result. The result has a length of two bytes, with the first
 *  -----------------  byte representing the measurement from the left half of the
 *  |   |   |   |   |  field, and the second byte the value for the right.
 *  |  c6   |  c7   |  
 *  -----------------
 *  |   |   |   |   |
 *  |  c8   |  c9   |
 *  -----------------
 *  |   |   |   |   |
 *  |  ca   |  cb   |
 *  -----------------
 *

....

/* With CS 5 we set the address of field, on CS 6 we get results. */
#define XU_CS_MESURE_FIELD 5
#define XU_CS_MESURE_FIELD_RET 6

....