This document describes the hardware architecture of the AM438x evaluation module (EVM), part number
TMDXEVM438x, which is based on the Texas Instruments AM438x processor. This EVM is also
commonly known as the AM438x Electronic Point of Sale (ePOS) EVM.
The AM438x ePOS EVM is a stand-alone test, development, and evaluation module system that lets
developers write software and develop hardware around an AM438x processor subsystem. The main
elements of the AM438x subsystem are already available on the base board of the EVM. The base board
gives developers the basic resources needed for most general-purpose type projects that encompass the
AM438x as the main processor. Furthermore, additional, common peripherals, such as memory, sensors,
LCD, Ethernet physical layer (PHY), and so on, are built into the EVM so that prospective systems can be
modeled quickly without significant additional hardware resources.
The following sections give more details regarding the EVM.
2System View
Figure 1 and Figure 2 show the system view of the AM438x ePOS EVM.
Description
SmartReflex is a trademark of Texas Instruments.
Micron is a registered trademark of Micron.
Samtec is a registered trademark of Samtech Inc.
The AM438x ePOS EVM has a camera board and/or wireless add-on boards. Figure 3 shows the block
diagram of the ePOS EVM.
Functional Blocks Description
3.1Processor
The following sections describe the major blocks of the ePOS EVM.
The AM438x processor is the central processor to this EVM. All the resources onboard surround the
AM438x processor to provide development capabilities for hardware and software. See the AM438x data
sheet and TRM for details about the processor.
System configuration signals (SYSBOOT0 to SYSBOOT18) on the EVM can be set using resistors and
switches to define some start-up parameters on the AM438x processor. See Section 5 for more details.
Several clocks in the EVM support the AM438x processor. The main clock for the processor is derived
from a 25-MHz crystal. An onboard oscillator in the AM438x device generates the base clock and
subsequent module clocks as needed within the AM438x processor. A 32-kHz clock for the real-time clock
(RTC) on the AM438x device is derived from a 32.768-kHz crystal on the board.
The EVM also supports an option to connect an external clock using a subminiature version A (SMA)
connector for both these clocks. However, hardware modifications are needed to isolate the onboard
crystals and connect the external clock. See the schematics and TRM for details.
3.3Reset Signals
Power-on reset to the processor is driven from the power good signal of the power manager and by a hard
reset switch. Asserting this switch also activates the reset signal SYS_RESETn, which runs to several
peripherals and the AM438x and resets those peripherals.
3.4Memories Supported
3.4.1LPDDR2 SDRAM
The AM438x ePOS EVM contains 8Gb (256M x 32, 2 dies) of LPDDR2 SDRAM memory from Micron®,
which has dual dies. The part number for the LPDDR2 SDRAM memory device used is
MT42L256M32D2LG-25. The package used is an 168-ball VFBGA package.
3.4.2NAND Flash
The ePOS EVM has a NAND type of flash. The part number of the memory device used is
MT29F4G08AB, which is a 4Gb (512M × 8) of flash memory. The GPMC signals are used to
communicate with this memory.
www.ti.com
3.4.3QSPI Flash
A QSPI flash of 512Mb, part number MX66L51235FMI-10G, is used in this design. The QSPI flash boot is
enabled through this flash. This flash is connected to the SPI0 port of the processor.
3.4.4Board Identity Memory
Each board contains a serial EEPROM that contains board-specific data that lets the processor
automatically detect which board is connected and the version of that board. Other hardware-specific data
can be stored on this memory device as well. The part number of the memory device is CAT24C256WI-G.
See Section 5 for details on the data in this memory.
3.5SDMMC0
The SDMMC0 connector on the ePOS EVM is a microSD card socket, part number MHC-W21-601. This
device is a standard SD/MMC card type of connector. The SDMMC0 connector is connected to the MMC0
port of the AM438x processor. Check the AM438x data sheet and TRM for supported card types and
densities.
3.610/100 Ethernet
The AM438x ePOS EVM uses the 10/100 Ethernet transceiver (DP83848J) from TI, which is connected to
the J8 RJ45 connector.
The reset on the transceiver is driven by the board system reset signal, SYS_RESETn, and the individual
reset signal, ETHER_RESETn, that is controlled by the GPIO of the AM438x processor. A 50-MHz crystal
oscillator drives the clock signal for the DP83848J device.
The AM438x ePOS EVM supports two USB ports. The USB ports are connected to a microAB connector
and a standard type-A connector. The ESD device, TPD4S012, and common choke filter, ACM2012
(TDK), are used on the USB signals before they are connected to the AM438x pins. The ID pin of the
microAB connector can be tied to ground through a J24 jumper to look like a B device.
3.8Connectivity
The AM438x ePOS EVM supports MCS COM8 form factor wireless boards from TI through the J21 COM
connector, which is a Samtec®card edge-type connector, part number MEC6-150-02-S-D-RA1. This
connector supports COM8 boards; more details are in the MCS COM8 board documents.
The COM connector requires 3.6 V, 442 mA on the power supply. Therefore a TPS79501 LDO regulator is
used to provide this voltage supply from the base 5.0-V supply.
The signals on the COM board are all 1.8-V voltage level. Therefore voltage translators are placed to
convert to and from 3.3 V of the AM438x rail for a particular signal that is running at 3.3 V.
3.9UART
This EVM supports two UART ports, UART0 and UART1. The UART0 port from the processor is
converted to USB using the FT2232HL USB-to-UART bridge. UART1 is terminated on a DB9 connector
using the MAX3243 RS-232 transceiver between the AM438x and the DB9 connector. UART0 can also be
optionally terminated with a DB9 connector and a RS-232 transceiver. The RS-232 and DB9 connectors
are unpopulated on the board.
Functional Blocks Description
3.10 ADC
The analog inputs to the AM438x device are terminated on the J36 connector, where a magnetic-stripe
assembly must be connected.
3.11 Smart Card
There is a full smart card connector FCI, part number 52400-25ALF, on the EVM. There are also three
SAM card sockets onboard. A TCA5013 Smartcard PHY controls these cards and is controlled by I2C2
from the AM438x.
The PHY I2C address is set to 0x3E.
3.12 Camera
Camera interface from the AM438x processor is terminated on the 12x2 header J15. The custom-made
camera module from TI shall be interfaced with this header. This camera module is on a separate camera
board that attaches at a right angle, so that the camera can face horizontally when the ePOS EVM is
laying on a testbench.
The I2C address set to camera module is 0x30.
3.13 Audio
This EVM uses an audio codec from TI, part number TLV320AIC3111, for the audio input and output. This
audio codec is connected through the McASP1 and I2C interfaces to the AM438x. The microphone is
implemented as a 3.5-mm jack with stereo connection. Speaker out is implemented with integrated
speakers. The PUI speakers are attached to the PCB and their solder lugs are connected to the
throughhole connections for each speaker. The audio codec reset is driven by the board system reset,
SYS_RESETn, and an individual reset signal that is controlled by a GPIO of the AM438x.
3.14 Printer Header
This EVM has a 2 × 12 header to connect to an external printer. The header connects several GPIOs, SPI
buses, and PWM signals to control a printer.
This EVM provides a 7-pin connector, part number 0533980771, to connect to the magnetic stripe reader.
The magnetic stripe reader is connected to the ADC analog inputs 0 to 7 of the AM438x processor.
4Power Supplies
This section describes how the power supplies required for the design are generated.
4.1Power Source
The AM438x ePOS EVM uses an external AC to +5 VDC (rated 2.5 A minimum) power adapter. The
switch near the power cable is used for powering on and off. The main power is on when the power switch
is positioned away from the power supply jack. The main power is off when the power switch is positioned
closest to the power supply jack.
4.2Power Sequencing
The power sequencing requirements of the AM438X processor (see the AM438x data sheet) are
automatically handled by the TPS65218 PMIC.
4.3Power-Management IC Power Supplies
The AM438x ePOS EVM uses the TPS65218 power-management IC from TI. The I2C0 on the AM438x is
used to control the SmartReflex™ port and control port on the TPS65218 device. For the AM438x
processor, the following power supplies from the TPS65218 device are used (see Table 1).
www.ti.com
Table 1. AM438x Power Supplies From TPS65218
TPS65218 Power SupplyAM438x Power RailVoltage (V)
VDCDC1VDD_CORE1.1 V
VDCDC2VDD_MPU1.1 V
VDCDC3VDD2, VDDCA, VDDQ of LPDDR21.2 V
VLS1VDD_DDR1.2 V
VDDS_CLKOUT, VDDS_OSC, VDDS_SRAM_CORE_BG,
V1_8D
V1_0BATVDD_TPM1.0 V
V1_8BATVDDS_TPM1.8 V
V3_3D_AM438X from
VDD1 of LPDDR21.8 V
NAND memory, QPSI flash, Ethernet PHY, SDMMC0, board ID memory, ARM
JTAG, buffers of FTDI section, LCD buffer, touchscreen, camera module, HDMI
buffer, audio codec, RS-232 sections, COM8 sections, smart card sections,
tamper header, platform test section, GPIO header, and printer
LCD POWER generation, camera module, VCOM_BAT generation for COM8
module, USB1 power generation, platform test section, LEDs, GPIO header,
buzzer, printer