USB Interface (USB)
2-3
Interfaces
2.3 USB Interface (USB)
The interface board connects to a USB port (version 1.1) on a host computer
and is powered from the port. All communication over the USB is proprietary
and does not fit any USB-defined device classes. Therefore communication
with the device requires a loader and driver from Texas Instruments.
The loader enumerates the device (determines it is present on the USB), then
loads the EV2300 controller firmware for the USB interface. Once the firmware
load is complete, the loader sends a command to the USB interface IC to
execute the new program and the loader driver exits. A new driver takes
control and enumerates the EV2300 and makes the device present to
programs running on the host.
The installer for the USB EVB installs:
1) A loader driver
2) A binary to load onto the USB interface IC
3) An EV2300 controller driver for direct access to the device
4) An EV2300 DLL for application access to the device
2.4 HDQ Interface (HDQ)
This interface allows a host computer to interact with a slave or target device
through the two-wire SMBus or the one-wire HDQ interfaces. The ports are
labeled with the corresponding signal names above each port connector.
Connect the signal and a ground reference (GND), and optionally VOUT, to a
target device.
The two-wire interface supports SMBus version 1.1 byte, word, block
transactions with and without PEC. The SMBus limits the capacitance on each
line (Data and Clock) to 100 pF. The EV2300 places 8 pF on each line, so a
device may place up to 92 pF total. If the capacitive load approaches or
exceeds 100 pF, SMBus communication may not be reliable.
Pin Name Description
1 GND Ground return/reference for HDQ interface.
3 HDQ HDQ one-wire interface. Pulled up to 3.3-V rail with a 10-kΩ re-
sistor.
4 VOUT Supplies 3.3 VDC to a target. Current load should be limited to
30 mA.
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