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User Interfaces
11
SPRUIF8 – June 2017
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Copyright © 2017, Texas Instruments Incorporated
AM438x ePOS EVM Hardware
6
User Interfaces
6.1
Keypad
The keypad has 4 × 4 push-button switches with Omron part number B3SL-1022P. The keypad is
replicated on the top and bottom of the board to allow the LCD to be swung out for hardware debugging of
the main components, or for the LCD to be mounted to the board for software debugging only. This
keypad uses 4 power lines and 4 scan lines to enable monitoring of 16 buttons. The buttons are arranged
mechanically as a standard 3 × 4 telephone dial pad and four arrow cursor directional buttons.
6.2
LEDs
There are four LEDs: red, yellow, green, and blue colors, on the top and bottom sides of the EVM. A
green power-on indication LED (D3) is available in the EVM.
6.3
Audio Buzzer
An audio buzzer is installed on the board to provide auditory cues to the user. This audio buzzer PUI
audio part number AI-1027-TWT-3V-R is driven from a GPIO.
6.4
Display
This EVM supports either LCD or HDMI display options. The AM438x DSS (display subsystem) signals
are connected to the LCD or HDMI display through the 32-bit, buffer/driver SN74LVC32244ZKE from TI.
The selection between LCD and HDMI is controlled by a GPIO of the AM438x.
6.4.1
HDMI
A Silicon Image SIL9022A HDMI transmitter converts the DSS signals to HDMI. The HDMI signals are
terminated at the HDMI connector-J32, part number 10029449-001RLF. SIL9022A is controlled by I2C2
from the AM438x. The HDMI reset is driven by the board system reset SYS_RESETn and an individual
reset signal that is controlled by a GPIO of the AM438x. For more details see the schematics.
The I2C Address of SIL9022A is 0X3B.
6.4.2
LCD and Touchscreen
The LCD signals are terminated at the 50-pin FPC connector (J44), part number FH12S-50S-0.5SH. The
LCD that mates with this connector is a 7-inch, WVGA (800 × 480) 24-bit, RGB, TFT LCD panel, part
number OSD070T1718-19TS. The connector supports 27 white LEDs for backlight (controlled by one
power regulator). The LED backlight on the LCD is controlled by a TPS61081 PWM controlled LED driver.
The LCD has a capacitive touchscreen that is connected to the I2C0 port of the processor. The required
power for the LCD is generated using the TPS65105 linear regulator supply.
The I2C address of the touchscreen is 0X5C.
7
Pin Use Description
7.1
Functional Interface Mapping
A pinmux configuration file is provided to show how each pin on the AM438x is configured on the EVM.
Most interfaces on the EVM are fixed to certain functions. See the AM438x data sheet to determine other
possible pin MUX configurations, to enable different functionalities for signals that are not fixed to certain
function board connectors.