Ocean Optics Apex - Manual (Page 9)

Apex Data Sheet
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Request Spectra
Initiates spectra acquisition. The Apex will acquire a complete spectra (2068 data values). The data is
returned in bulk transfer mode through EP2. The table below provides the pixel order for the two
different speeds. The pixel values are decoded as described below.
Byte Format
Byte 0
0x09
Return Format
The format for the returned spectral data is dependant upon the USB communication speed. The
format for both High Speed (480 Mbps) and Full Speed (12Mbps) is shown below. All pixel values are
16 bit values which are organized in LSB | MSB order. There is an additional packet containing one
value that is used as a flag to insure proper synchronization between the PC and Apex.
Note
Apex has 2068 pixels. It reads out 4609 bytes, some of which are filler: bytes 0-4135
correspond to pixels 0-2067, bytes 4136-4607 are filler, and byte 4608 is a sync byte.
USB High Speed (480Mbps) Packet Format
. In this mode, all data is read from EP2In. The packet format is described below.
Packet # End Point # Bytes Pixels
0 EP2In 512 0-255
1 EP2In 512 256-511
2 EP2In 512 512-767
3 EP2In 512 768-1023
4 EP2In 512 1024-1279
5 EP2In 512 1280- 1535
6 EP2In 512 1536-1791
7 EP2in 512 1792-2047
8 EP2In 512 2048-2303
9 EP2In 1 Sync Packet
The format for the first packet is as follows (all other packets except the synch packet has a similar
format except the pixel numbers are incremented by 256 pixels for each packet).