US Digital

The USB1 is a data acquisition device designed to track up to 4 incremental encoders and 8 digital inputs. Each of the 4 external encoders has a dedicated 24-bit real-time hardware up / down counter. The internal microcontroller then reads and stores the value of all four counters, the 8 digital inputs, and a 32-bit time stamp at a rate configured by the user. This historical buffer can be downloaded to the PC using the USB interface at any convenient time, even while continuing to store more samples in the internal circular buffer. The USB1 also includes the capability to use either encoder position changes or combinations of digital inputs as triggering and / or storage qualification events.

Eight relay driver type digital outputs are provided along with an SEI port that can read up to 15 US Digital absolute encoders per device. When a "1" is written a digital output port bit, the driver is asserted and the corresponding port pin is clamped to ground by a MOSFET transistor (it is an inverting 'open-collector' configuration). The USB1 takes advantage of the robustness, speed, and easy configurability of the Universal Serial Bus architecture while providing a simple and consistent software interface for the encoders and inputs that it tracks. The USB1 is intended for use with computers that have at least one free USB port and are running the Windows 98/ME/2000/XP operating systems. The USB1 is fully compatible with USB expansion hubs, allowing multiple USB1 units to be used on a single computer.

The USB1 is powered by a standard US Digital regulated DC power supply (PS-12). The USB1 provides 5VDC power to the encoders and digital I / O connectors. The USB1 may be instructed to retain configuration settings (but not count values) when power is removed. If power is lost, the incremental counters reset to zero.

The USB1 supports both indexed and non-indexed encoders in x1, x2 or x4 counting modes. Its four independent counters are able to respond to quadrature frequency rates of up to 1 MHz, with a counting range from 0 to 16,777,215. The USB1 command protocol provides access to a control register for each channel, allowing individually programmable count modes of Normal Count, Modulo-N, Non-recycle, and Range Limit for each channel. The USB1 may be configured in software to zero a channels counter when an encoder index signal is asserted.

The SEI port on the USB1 is designed for US Digital's SEI based products, such as the A2 absolute encoder. The baud rate of the SEI port is fully programmable, and supports baud rates from 2400 to 57,600 bps.