Kramer Electronics VP-790 - Manual (Page 5)

VP-790 Protocol – Communication 1
1 Communication
1.1
2B
API Call
Communication between the PC and the Scaler Board is through remote API calls
and corresponding answers.
All the values indicated blue are fixed. They need to be sent or
received, but the values will not change in the given context.
An API function call has a 16 Byte logical header, followed by a 16 byte application
Header, followed by the data package of variable length. The logical header for
RS232 based API calls is (hex):
53 41 50 01 FF FF FF FF ww xx yy zz 00 00 00 00
ww xx yy zz is the payload size (type UWORD32) of the following transmission in
bytes (application header size (16 bytes) + data package size of variable length).
The application header for API remote calls is (hex):
54 50 01 00 00 00 00 00 ww xx yy zz 00 00 00 00
ww xx yy zz is the payload size (type UWORD32) of the following transmission in
bytes (data package size of variable length).
The data package carries the information on the API called and all (Input)
parameter values (hex):
50 46 uu vv 00 00 00 00 ww xx yy zz data
uu vv is the Index (type UWORD16) of the API to be called. ww xx yy zz is the size
of the parameter data buffer. data are the parameter values to be passed. The
ordering has to be matched with the API prototype parameter ordering and size.
Example: The brightness shall be changed. Brightness is changed by calling API
function BYTE byOSDBrighntessSet(UWORD32 u32_value). This API has the
index 0x0068 and the parameter is a 4 byte value. Let us assume we want 50% of
the available brightness, i.e. u32_value = 0x7FFFFFFF.
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