Front Panel PCA
The plotters use the same front5panel PCA as the DeskJet 550. The front5panel consists of nine LEDs and eight switches, mounted on the PCA, which is deeply recessed behind a plastic housing containing the key pad. The keys act on the switches through push rods. Light pipes transmit the light from the LEDs to the display area.
LEDs
The LEDs are driven by drivers on the main board, under the control of the servo processor. The LED layout is shown below:
led[1] | led[4] | led[7] |
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led[2] | led[5] | led[8] |
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led[3] | led[6] | led[9] |
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Key Pad
The keypad layout is shown below:
led[2] | led[3] | led[6] | led[7] |
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| key[0] |
Switch[1] | Switch[2] | Switch[3] | Switch[4] | |
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| key[1] |
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Switch[5] | Switch[6] | Switch[7] | Switch[8] | |
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The switches are connected as a 4x2 matrix. The switch matrix, when scanned, is driven by the four LED control signals led[2], led[3], led[6] and led[7]. The servo processor scans the switch matrix by setting, in turn, each of the four control signals to `0' while holding the other three at `1'. While driving the switch matrix, the processor reads the signals key[0], and key[1]. A `1' on a key signal indicates a closed switch.
C3187590000 | FunctionalOverview 5531 |