Texas Instruments TUSB2136 - Manual (Page 14)

Setup
3-2
3.1 Setup
The USB keyboard/hub EVM is designed to allow evaluation of the TUSB2136
and the TPS2149 device. Test points and 0-
Ω
resistors are provided to simplify
the evaluation process (see section 3.5). The EVM comes in a default
configuration that requires no additional components, other than the required
hardware and software identified in Section 1.1 of this user’s guide. For a
complete description of the TUSB2136 and the TPS2149 devices, consult the
TUSB2136 and the TPS2149 data sheets (literature numbers SLLS442 and
SLVS401, respectively).
3.2 Interfaces and USB Ports
The EVM uses a standard Type-B connector for the upstream port and two
single Type-A connectors for the downstream ports. Power to the downstream
ports is provided from the upstream USB 5-V source through the TPS2149.
Two edge connectors, J3 and J4, connect to the TUSB2136 general-purpose
I/O lines. Out of 32 general-purpose I/O lines, 26 are brought out to the J3 and
J4 connectors. The remaining 6 I/O lines are used onboard to control the LEDs
(see Light Emitting Diodes (LEDs) in this chapter).
3.3 Power Supplies
The USB keyboard/hub EVM requires no external power supply for operation.
The EVM receives power via the upstream USB cable. The USB 5-V source
is limited by the USB specification to 500 mA max. The TPS2149 low-dropout
regulator is used to generate the required 3.3-V supply from the USB 5-V
supply. The power indicator LED (D1) turns on whenever power is available
to the EVM (see Table 3–1).
3.4 Light Emitting Diodes (LEDs)
Several onboard LEDs are provided on the EVM for quick and easy evaluation.
A set of six green LEDs (D2 – D7), connected to P3.0 through P3.5 of the
TUSB2136, may be used for general purposes in any code that is written for
the TUSB2136 (see Table 3–1). By default, the factory code provides the EVM
with the use of only three of the LEDs as keyboard status indicators for Scroll
Lock (D2), Caps Lock (D3), and Num Lock (D4). The other three are not used.
Table 3–1. LED Description
LED Description
D2–D7 Green LED ON indicates corresponding GPIO pin is low (when D1 is ON).
Green LED OFF indicates corresponding GPIO pin is high (when D1 is ON).
D1 Red LED ON indicates that the EVM is powered on and not suspended.
Red LED OFF indicates that the EVM is powered off or suspended.