BitFlow Cyton-CXP, Справочник по аппаратуре

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Encoder The Cyton-CXP
CYT-9-4 BitFlow, Inc. Version A.0
9.3 Encoder
9.3.1 Encoder Input Types
There are three encoder inputs.
ENCODER_TTL - Single ended TTL level encoder
ENCODER_DIFF - Differential (LVDS) encoder
ENCODER_OPTO - Optocoupled encoder
The hardware encoder is enabled/disabled by the bit EN_ENCODER. Only one input
at a time is active (the software encoder bit, SW_ENC, is always active). The active
encoder is selected by the bitfield SEL_ENC. The current level of these inputs can be
read from software by reading the bits RD_ENC_DIFF, RD_ENC_TTL and RD_
ENCOPTO. The unselected inputs will have no effect on the board. However, they can
be used as general purpose inputs.
9.3.2 The Optocoupled Encoder
The opto-coupled encoder allows the acquisition circuitry to accept an encoder sig-
nal without having a galvanic connection to the encoder source. This is mandatory in
some medical and industrial application. The encoder information is passed as a light
pulse from an on-board LED that is coupled to a receiving phototransistor. The LED
and the phototransistor are in the same package, a Sharp PC3H711. Figure 9-2 shows
the electrical diagram of the optocoupled encoder circuit and a suggested circuit for
the driver. The LED is driven by an open collector driver. The user must supply his +5V
power to the LED. Note that there is no galvanic connection between the user’s circuit
and the acquisition circuitry.