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Video Overlay Board Connections

This page gives instructions for the connection of the RTCKBD video overlay board to power, video in and video out.

Power and Video Connections

The positions for the connection of power, video in and video out are clearly marked on the video overlay board shown in insert A below right. A 9 - 12V DC regulated power supply should be connected to the points marked +12V and 0V as shown in inserts B and C, close up, below right. Care should obviously be taken in connecting the power supply. Although the designated power connection points are protected against accidental reverse polarity connection, connecting the power elsewhere on the board will result in its failure. Our warranty specifically excludes failure due to improper connections. Please ensure that all soldering or other connection work is done in accordance with these instructions.

The video connections shown in this example are made with screened coaxial cable suitable for video signals. The lapped screen which carries the video ground from the camera is connected to the video ground on the board. Care should be taken to ensure that the video grounds and power ground are connected separately.

5V Power Connections

The 9 - 12V DC regulated power supply is reduced to 5V DC by the 500mA switch mode regulator on the video overlay board. This 5V output is available to power a PC keyboard or user designed circuit. The connection point for the 5V output is shown in the highlighted insert below left, marked 5V. WARNING: There is no polarity protection on the 5V output. Short circuiting this point on the board to ground, either directly or via the attached circuit, will damage or destroy the video overlay circuit. The warranty is void in such cases. The board may also be powered from an external circuit with a 5V power supply connected to this point.

RTCKBD Keyboard Connections

To connect the RTCKBD video overlay board to a PS/2 or USB connector follow the layout and example below.

RTCKBD Keyboard connections

USB Connector pin out

Pin No. Signal Board Connection Point
1 Vcc 5V 5V
2 Data - DATA RB3
3 Data + CLK RB0

PS/2 Connector pin out

Pin No. Signal Board Connection Point
1 N/C
2 5V 5V
3 N/C

RTCKBD - Counter Connections

The on screen counter is driven by a TTL rising edge on RB6 as shown below. The direction of the count is determined by the state of RB7. If the RB7 pin is TTL high then the count is positive. If it is TTL low then the count is negative. The counter increments / decrements by 1 between +9999 and -9999. Please note that the counter is not a direct distance measurement. You will need to know the counts per turn and turns per distance measurement given by the encoder used to read the display. A prescale constant between 1 and 2048 can be set to allow the counter display to be adjusted to match the external count source. The position of the decimal point in the count display can be changed to one of four positions. The direction pin is pulled high internally to give a positive count by default if left unconnected. When used with an incremental rotary encoder connect channel A to RB6 and channel B to RB7 as shown.

Counter Pin RB6 0 - 5V TTL, count on the rising edge
Direction Pin RB7 5V TTL logic high for + count, 0V TTL logic low for - count
Ground GND Common Ground

Anti-clockwise rotation - positive count

When the encoder is rotated anti-clockwise, each rising edge of channel A occurs when channel B is high. This gives a positive count.

Clockwise rotation - negative count

When the encoder is rotated clockwise, each rising edge of channel A occurs when channel B is low. This gives a negative count.

Counter Reset Connections

The counter can be reset either from the keyboard or from a reset button connected to the board as shown below. The counter value is preserved when power is removed from the unit.



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