GVG style wipe control

RS422 control at 38k4 baud

INIT                Sent on startup (could be ignored by the wipe generator)
Break, 0x30

WRITE WIPE TYPE Horizontal
0x03,0x01,0xC8,0x0A

WRITE WIPE TYPE Vertical
0x03,0x01,0xC8,0x00

REVERSE WIPE OFF
0x03,0x01,0xC7,0x1D

REVERSE WIPE ON        Swap foreground and background
0x03,0x01,0xC6,0x1D

TBAR POSITION
0x05,0x01,0xC5,0x00,lsb,msb

lsb is 3,2,1,0,X,X,X,X
msb is 11,10,9,8,7,6,5,4
12 bit resolution

so
0x05,0x01,0xC5,0x00,0x00,0x80
is a 50% wipe