DEVA Deva037, User Manual, Page: 21 / 24

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Deva037 USB Encoder Interface User’s Manual
USB Incremental Encoder Interface Hardware
4.1.4 USB connection
USB connection is via a B connector, whilst internal USB connection is via a 4-pin header.
Pin Number Signal
1 +5V
2 Data0-
3 Data0+
4 0V
4.1.5 Internal Encoder Power
The internal encoder power is via a 4-pin right-angle male Molex 8981 connector. The +5V
and +12V from this connector are routed via 1Amp resettable fuses to the encoder
connections.
Pin Number Signal
1 +12V
2 0V
3 0V
4 +5V
4.1.6 Optical
Optical connections are via a Fibre-SMA connector. The optical signal connector is at the
bottom of the stack and the reference connector is at the top of the stack.
4.2 Functional description
The Deva037 is designed to interface up to three incremental encoders or linear scales to the
USB bus.
The functions are programmed via Deva’s proprietary interface Enclib and/or,
where the device is to be used in a CMM application, a utility such as DevaCMMCtrl.
The following sections describe the various functions of the interface. For detailed
description of how to program these facilities, please refer to the Enclib and/or DevaCMMCtrl
User’s Manual.
4.2.1 Quadrature input
Each encoder channel has four differential / single ended input circuits designated A, B, Z and
M. The A and B inputs accept the quadrature signals from the encoder and drive an up/down
counter via a x4 directional discriminator circuit. The counter has 32-bit resolution and may
be read at any time. The maximum count rate is in excess of 10MHz.
4.2.2 Marker input
The M input circuit designated marker is a positive edge triggered input which can
synchronously latch the counter value. To gain the most accurate result the input
conditioning circuit latches the counter when both A and B inputs are at a logic one level.
The user must therefore phase the A and B signals carefully to meet this criterion. Should
this not be achievable, circuit operation is still possible although the latched value will not be
accurate to a single count. Correct phasing may also be achieved by using the input inverters
on signals A, B and M.