Video input & output ports

AN2471

4/12

2

Video input & output ports

STMAV335 can switch three sets of video input to a single set of video output. On the

evaluation board, the three sets of video input are:

1.

RGB (VGA port)

2.

YPbPr (3 RCA connector)

3.

CVBS (RCA connector) & S-VIDEO ( S-connector)

In the real system, the outputs of STMAV335 are directly connected to the video receiver.

However for the STMAV335 evaluation board, each output line branches to three signal

lines. The reason for this is because each set of different video signal has a different type of

connector. During evaluation, each output line should be branched and be connected to a

different video connector on the display unit back panel by a cable.

To avoid any PCB trace stub, the 1 to 3 branching of each output line cannot be shorted on

the board. The branching of the output line is done by a zero ohm resistor. Depending on

which particular set of video signal is active, the zero ohm resistors should be soldered such

that the output of STMAV335 is connected to the right video output connector.

Note:

SEL1

→ JP9, SEL2 → JP10, OPEN = '1' & CLOSE = '0'

2.1

Video input conditioning

The blanking level might vary between different video transmitters. This STMAV335

evaluation board can handle video signals with blanking level of 0V to 2.5 V.

If video signal blanking levels are outside the above range, some input conditioning should

be done to modify the blanking level to the range specified.

Table 2.

Evaluation board video input & output

Input

Output

SEL

0

Ω Jumper output

RGB (VGA_IN)

RGB (VGA_OUT)

SEL1 = ‘1’

SEL2 = ‘0’

J11 = ‘R’

J12 = ‘G’

J13 = ‘B’

Y (Y_IN)

Pb (Pb_IN)

Pr (Pr_IN)

Y (Y_OUT)

Pb (Pb_OUT)

Pr (Pr_OUT)

SEL1 = ‘0’

SEL2 = ‘1’

J11 = ‘Y’

J12 = ‘Pb’

J13 = ‘Pr’

CVBS (CVBS_IN)

S-VIDEO

(S VIDEO_IN)

CVBS (CVBS_OUT)

S-VIDEO

(S VIDEO_OUT)

SEL1 = ‘0’

SEL2 = ‘0’

J11 = ‘CVBS’

J12 = ‘Y(S)’

J13 = ‘C’