ETRA SOM/ETRA Evaluation Kit/pdf

Getting started

Kit Identification Codes

The development kits are identified by a couple of codes:

1. P/N Part Number identification code
2. S/N Serial Number identification code

These codes are printed on a label stuck to the box containing the kit.

For example, the following picture shows such a label of an AXEL Lite Evaluation Kit with Serial Number 0DE7

Label of AXEL Lite Evaluation Kit

These codes are required to complete the registration process of the kit.

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Unboxing

Once you've received the kit, please open the box and check the kit contents with the packing list included in the box, using the table on this chapter as a reference.

The hardware components (SOM, carrier boards and display) are pre-assembled, as shown in the picture below:

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Kit Contents

The following table list the kit components:

Component	Description
	ETRA SBC SoC: STM STM32MP157AAB3 (STM31MP1 Dual Core - 650MHz - Tj=-40/125°C) SDRAM: 512MB eMMC: 8GB
	Ampire AM-800480BTMQW-TBMH-A 7” 800x480 RGB display
	AC/DC Single Output Wall Mount adapter Output: +12V – 2.0 A
	FTDI TTL/USB cable (TTL-232RG-VIP-WE)
	MicroSDHC card

Order codes

Order code	Description
SDCSB70000D1R-00	This code refers to the default configuration detailed above including SOM S-DSDAE09300I1R

microSD Layout

The microSD provided with the kit is used to store:

• a bootable partition (mmcblk0p1, vfat) containing:
  • binary images (u-boot and kernel images)
• root file system partition (mmcblk0p2, ext4)

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Connections

This section describes how to quick start the Evaluation Kit. The picture below shows the ETRA SOM inserted into the Evaluation Kit:

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The system is programmed to automatically boot Linux at power up, loading the bootloader, the kernel and device tree image and the root file system from the SD card memory.

To connect to the system:

• insert the SD card into the micro SD slot
• connect the 12Vcc power supply to J1 on the board
• connect the USB to TTL UART adapter to the J2 connector on the SBC and connect the USB side connector to an USB port on your computer
  • if required, install the FTDI USB to serial driver
  • start your favorite terminal emulator software on PC (eg: PuTTY, Minicom, ...); communication parameters are 115200,N,8,1
• (optional) connect the ethernet cable from your LAN hub/switch to the J5 RJ45 connector
  • start SSH, using the following parameters:
    • ip address: 192.168.0.89
    • username: root
    • empty password

Warning: please, pay attention to the debug cable header connection, see the picture here below:

First boot

Once power has been applied, U-Boot bootloader will be executed and the debug messages will be printed on the serial console. U-Boot automatically runs the autoboot macro, that loads the kernel/dtb and launches it with the options for mounting the root file system from the SD card.

At the end of the boot process, a demo application is launched and you can interact with the system using the touchscreen. The Linux shell is available on the serial console. Moreover, both telnet and ssh services are available to connect to the system through the network.

Serial console

A simple Windows serial and SSH/telnet client and terminal can be downloaded from here.

The following picture shows the serial setup for connecting to the EVK:

PuTTY connection using Serial Port

once selected the COM[x] serial port, click the Open button which starts the terminal. Once powered, the EVK shows the U-boot debug messages printed on the serial console.

Connecting through SSH

The following picture shows the SSH connection to the EVK:

PuTTY connection using SSH

once selected the IP address, click the Open button which starts the terminal. Once connected, the EVK shows the linux kernel prompt login for inserting the login:

PuTTY SSH login

Then use the root login username without password:

PuTTY SSH connected

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Boot Configurations

ETRA Evaluation Board is built upon STM32MP1 processor.

The following sections detail boot configuration options, which differ depending on the SoM.

Available options

Boot modes can be selected by S1 DIP-switch which acts directly on BOOT_MODE[2..0] configuration pins.

S1 switches are connected to ETRA BOOT_MODE[2:0] pins allowing different boot modes.

S1 boot switches

where S1 switches are mapped as the following table:

BOOT_MODE	S1	Note
BOOT_MODE0	S1.1
BOOT_MODE1	S1.2
BOOT_MODE2	S1.3
-	S1.4	USB OTG settings

DIP settings

BOOT_MODE[2:0]	S1[3..1]	Boot peripheral	Notes
000	OFF-OFF-OFF	USB	boot from USB OTG
001	OFF-OFF-ON	NOR	boot from NOR flash on Quad-SPI
010	OFF-ON-OFF	eMMC	boot from eMMC on SDMMC2
101	ON-OFF-ON	SD	Default boot from SD card on SDMMC1
111	ON-ON-ON	NAND	boot from NAND flash on Quad-SPI

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Reset Button

ETRA Evaluation Board has a pushbutton directly connected to the PMIC.RSTN signal which drives a PMIC hardware reset.

S2 is the hardware reset button.

Reset button

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General Information

Product Highlights

The SBC ETRA platform presented here provides a compact solution for any industry and can be easily interfaced with Plant Automation Control thanks to IEC-61131 SW language environment and/or other plug-ins like QT framework or multimedia GStreamer video applications.

The following table summarizes the main hardware and software features available with SBC ETRA:

Hardware

Subsystem	Characteristics
CPU	STMicroelectronics STM32MP1 Solo/Dual core
USB	Host and OTG
Storage	onboard eMMC or NAND, uSD connector
Serial Ports	dual RS232/485 port
Ethernet	10/100Mbps
Display	WIDE™ interface with 18- or 24-bit RGB
Video	2 lane MIPI interface
Touchscreen	USB capacitive
Connectivity	Bluetooth and Wi-Fi
LED and Buttons	(optional) membrane with up to 6 LED and 2 buttons
PSU	12 to 24V DC or 5V from USB
Mechanical Dimensions	87x68mm - Standard DIN (4modules)

Software

Subsystem	Options
Operating System	Linux
Distribution	Yocto
Graphical Framework	Qt

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Block diagram

The following picture shows a simplified block diagram of the ETRA SOM Evaluation kit.

Main functional subsystems and interfaces are depicted.

ETRA Evaluation kit peripheral blocks

The heart of the Evaluation Kit is the ETRA SOM module: please refer to the following Product Highlights page for the Evaluation Kit product highlights information.

Here below a summary for the main characteristics of the Kit.

Features Summary

Feature	Specifications
Supported SOM	integrated on carrier board
Serial Ports	2x UART RS232/RS485 1x LVTTL UART on pin strip (debug port)
Connectivity	1x 10/100TX Ethernet on RJ45 connector DWM Wireless module (optional)
Display	WIDE™ display interface 2 lane MIPI interface
Storage	1x microSD slot 1x eMMC on board device (optional)
USB	1x USB 2.0 Host port 1x USB OTG port
Miscellaneous	Capacitive touchscreen connector GPIOs ADCS DACs JTAG RTC battery user LED and Buttons (optional)

Electrical, Mechanical and Environmental Specifications

Electrical / Mechanicals	Specifications
Supply voltage	+ [12 - 24] V or +5V from USB OTG port
Dimensions	86 mm x 68 mm
Weight	TBD g
Operating Temperature	-5/+65 °C

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Carrier board design guidelines

This page provides useful information and resources to system designers in order to design carrier boards hosting DAVE Embedded Systems system-on-modules (SOM).

These guidelines are provided with the goal to help designers to design compliant systems with DAVE Embedded Systems modules and they cover schematics and PCB aspects. They apply to several products that are listed on the top right corner of this page (see "Applies to" boxes).

Basic guidelines

In this section basic hardware guidelines valid for all DAVE Embedded Systems SOMs are detailed.

Schematics

• Check mirroring and pinout of DAVE Embedded Systems system-on-modules (SOM) connector
• Properly decouple DAVE Embedded Systems system-on-modules (SOM) power supply with large bulk capacitor and small bypass capacitor
• Use low-ESR X7R capacitor if possible
• Check for correct connection of TX and RX lines
• Add series resistors as interface needs (see interface details)

PCB

PCB Tecnology

Use a PCB technology as advised in the following table

Parameter	Min	Typ	Max
Layers(number)	4	6	-
Power Plane Layers	2	4	-
Clearence(mils)	-	6	-
Trace Width(mils)	-	6	-
Vias hole (mechanical)	0,3		-
Minimum number of via for each power signal layer changes	2	3	-
Minimum number of via for each power signal SOM connector pin	1	2	-
Component package size	-	0603	-
PCB Height(mm)	1,4	1,6	-

• If vias smaller than minimum advised size are used, take care to maintain an adeguate number of via when you change layer for each power signal.
  
• PCB heights less than minimum advised can produce PCB heating and mechanical issues

PCB Basics Guidelines

• Avoid stubs
• Isolate clock and HI-SPEED signal (see interface specifications for further details)
• Avoid voids on planes
• Use Solid Connection for on plane vias
• Place bulk and ByPass capacitor near DAVE Embedded Systems system-on-modules (SOM) power supply pins
• Place series terminator resistor near the related transmitter

SOM Connectors

This section provides information and suggestions regarding the SOM mating connectors.

SO-DIMM

SO-DIMM mating connectors from different vendors may have slight differences in mechanical characteristics. One critical point is the position of the end of the mating area (please see the picture below), that can be slightly shifted inwards or outwards in respect to the retention holes on the carrier board. This can lead to a misalignment with the holes on the SO-DIMM modules, making difficult or impossible to insert the retentions screws or locking supports.

If you plan to use the holes as additional retention system, we recommend to pay attention to the mechanical characteristics when evaluating the SO-DIMM mating connectors to be mounted on the carrier board.

Power-up sequence

In order to prevent back powering effects, DAVE Embedded Systems' SOMs provide the signals required to handle power-up sequence properly. For instance, see the recommended sequence for the BORA SOM here.

In case the power-up sequence is not managed properly, the circuitry populating the SOM may be damaged.

Interfaces Guidelines

This section provides guidelines for the most used interfaces on DAVE Embedded Systems SOMs module.
Please refer to SOM's detailed pages for specific additional information.

Ethernet 10/100/1000

Case #1: PHY is integrated on SOM

This section refers to the case of PHY integrated on SOM such as Lizard and MAYA.

Schematics

• If LAN connector with integrated magnetic is used:
  • predispose ethernet protection diodes on ethernet lines
  • Connect connector shield to an adeguate GND or shield Plane

PCB

Refer to this table for 10/100 differential pairs routing

Parameter for 10/100 differential pair	Min	Typ	Max
Differential Impedance(ohm)	-	100	-
Common Mode Impedance	-	50	-
Gap than TX and RX signals	2xgap	2xgap	-
Gap than other signals	2xgap	4xgap	-
Intra pair matching(mils)*	0	25	150
TX and RX via # mismatch*	0	0	1

Refer to this table for Gigabit differential pairs routing

Parameter for Gigabit Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	-	100	-
Common Mode Impedance	-	50	-
Gap than TX and RX signals	2xgap	2xgap	-
Gap than other signals	2xgap	4xgap	-
Intra pair matching(mils)*	0	10	10
Max PCB trace length	3"	5"	-
TX and RX via # mismatch*	0	0	1

* Not mandatory but recommended.

• If LAN connector with integrated magnetic is used:
  • do not route traces under the connettor, neither on opposite side
  • place filter diode near connector
  • place others signals far from connector
  • Connect connector shield to an adeguate GND or shield Plane or Copper through numerous vias
• If on board magnetic are used
  • adeguately isolate system GND from magnetic connector side
  • Connect connector shield to an adeguate GND or shield Plane or Copper through numerous vias if necessary
• try to match as best as possible each differential pair (intrapair matching)
• Keep as best as possibile the same route for TX and RX traces
• If less than minimum gap is used, use a GND trace for improve trace separation

Case #2: PHY is not integrated on SOM and a RGMII PHY is used

This section refers to the case of:

• PHY not integrated on SOM
• Gigabit PHY populated on carrier board and connected to SOM through RGMII interface.

This solution is implemented on NaonEVB-Mid for example.

Schematics

• Add series resistors (RPACK resistors recommended) to RGMII lines
• Properly decouple PHY Power Supplies rails
• Properly decouple every supply pin of Ethernet PHY
• Properly separate analog Supply Rails

PCB

Parameter for RGMII interface	Min	Typ	Max
Common mode impedance(ohm)	-	50	-
Gap than other ethernet diff pair	4xwidth	-	-
Gap than other signals	4xwidth		-
Matching(mils)	-	-	200
Via Mismatch	0	0	1

Parameter for Gigabit Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	-	100	-
Common Mode Impedance	-	50	-
Gap than TX and RX signals	2xgap	2xgap	-
Gap than other signals	2xgap	4xgap	-
Intra pair matching(mils)	0	10	10
Max PCB trace length	3"	5"	-
TX and RX via # mismatch*	0	0	1

* Not mandatory but recommended.

• Ground and VCC planes must be as large as possible
• Avoid plane split and voids
• Place bypass capacitor near every PHY supply pin
• Connect every capacitor's pin to the plane with at least 2 vias and the shortest trace pattern
• Place PHY device at least 1" (25mm) distance far away from connector
• Keep MDIO clock signal isolated from other signals

Case #3: PHY is not integrated on SOM and a RMII PHY is used

This section refers to the case of

• PHY not integrated on SOM
• 10/100 Ethernet PHY populate don carrier board and interfaced to SOM through RMII interface.

This solution is implemented for example in MayaEVB-Lite board.

Schematics

• If possible, place series resistor to RMII interface signals
• Properly decouple PHY Power Supplies rails
• Properly separate analog Supply Rails
• Properly decouple every supply pin of Ethernet PHY
• Use a standard RMII PHY that supports correct clock mode (see SOM specification for further details)

PCB

Parameter for RMII interface	Min	Typ	Max
Reccomended Common mode impedance(ohm)	-	50	-
Gap between other signal	2xW		-

• Since RMII signals are not critical such as RGMII, is not necessary a strong matching between signal
• Avoid use of long traces
• Avoid stubs
• Keep as best as possibile the same routing for all RMII traces

Parameter for Ethernet Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	-	100	-
Common Mode Impedance	-	50	-
Gap than other TX and RX signals	2xgap	2xgap	-
Gap than other signals	2xgap	4xgap	-
Intra pair matching(mils)*	0	25	150
TX and RX via # mismatch*	0	0	1

* Not mandatory but recommended.

• Ground and VCC planes must be as large as possible
• Avoid plane split and voids
• Place bypass capacitor near every PHY supply pin
• Connect every capacitor's pin to the plane with at least 2 vias and the shortest trace pattern
• Place PHY device at least 1" (25mm) distance far away connector
• Keep MDIO clock signal isolated from other signals

USB

Schematics

• Create schematic in accordance with DAVE Embedded Systems system-on-modules (SOM) USB specification ( see SOM detailed pages )

PCB

Parameter for USB Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	80	90	100
Common Mode Impedance	40,5	45	49.5
Gap than other signals	3xgap	5xgap	-
Intra pair matching(mils)	0	25	150
Max allowed stubs	-	-	0
Max traces length	-	-	note 1
Max allowed plane split under traces	-	-	0

note 1 see SOM detailed specifications

• If a stub is unavoidable in the design, no stub should be greater than 200 mils.
• Place a continuos reference plane underneath differential pair

HDMI

Schematics

• Add a Transmitter Port Protection to HDMI lines
• Use certified HDMI connector
• Connector shield must be properly connected

PCB

Parameter for HDMI Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	85	100	115
Gap than other signals	3xgap	5xgap	-
Intra pair matching(mils) at 225MHz clock	0	20	250
Inter pair matching(mils) at 225MHz clock	0	250	1"
Max allowed stubs	-	-	0
Max allowed plane split under traces	-	-	0

• Place a continuos reference plane underneath differential pair
• Try to match lines as best as possible

SATA

Schematics

• Use certified SATA connector

PCB

Parameter for SATA Differential Pairs	Min	Typ	Max
Differential Impedance(ohm)	80	100	120
Common Mode Impedance(ohm)	51	60	69
Gap than other signals	2xgap	-	-
Intra pair matching(mils	-	-	note 1
Inter pair matching(mils)	-	-	note 1
Max allowed stubs	-	-	0
Max allowed plane split under traces	-	-	0
Max allowed length	-	-	note 1

note 1 see SOM detailed specifications

• Place a continuos reference plane underneath differential pair
• Minimized vias use
• No strong matching required between TX and RX, but keep same route for every differential pair

PCI Express

PCB

Parameter for PCI Express Differential Pairs	Min	Typ	Max
Differential Impedance [Ohm]	-	100	-
Common Mode Impedance [Ohm]	-	60	-
Gap than other signals (reccomended)	-	2xgap	-
Intra pair matching [mils]*	-	-	10
Max Total Length [in]*	-	-	12
Maximum allowed stub	-	-	0
Max allowed vias	-	-	6

• * Including SoM trace length
• Preferred underneath plane over entire trace length GND.

LVDS

PCB

Parameter for LVDS Differential Pairs	Min	Typ	Max
Differential Impedance [Ohm]	85	100	115
Common Mode Impedance [Ohm]	46.75	55	63.25
Gap than other signals (reccomended)	-	2xgap	-
Intra pair skew [mils]*	-	-	5
Inter pair skew [mils]**	-	400	-
Maximum allowed stub	-	-	0

• Prefer to route traces on TOP layer, referring them to a continuos GND plane.
• * Not includes SOM's length.
• ** Typical value can be relaxed depending on LVDS clock frequency

LCD Interface

Schematics

• Please refer to DAVE Embedded Systems system-on-modules (SOM) carrier board documentationfor further information
• Predispose series resistor terminator (RPACK for LCD data and single resistor for Clock and H-SYNC and V-SYNC)
• Series resistor value may vary depending by PCB and schematic

PCB

• If possible, use 50ohm common mode lines
• Match LCD parallel signals in accordance with Pixel Clock frequency (further details in SOM specifications)
• Avoid use of long traces connection (max 10" on PCB)
• Avoid stubs

VIN Interface

Schematics

• Please refer to DAVE Embedded Systems system-on-modules (SOM) carrier board documentation for further information
• Predispose series resistor terminator (RPACK for LCD data and single resistor for Clock and H-SYNC and V-SYNC)
• Series resistor value may vary depending PCB and schematic

PCB

• If possible, use 50ohm common mode lines
• Match VIN parallel signals in accordance with Pixel Clock frequency (further details in SOM specifications)
• Avoid use of long traces connection (max 10" on PCB)
• Avoid stubs

TVOUT

Schematics

• Please refer to DAVE Embedded Systems system-on-modules (SOM) carrier board documentation for further information

PCB

Parameter for SATA Differential Pairs	Min	Typ	Max
Common Mode Impedance(ohm)	-	75	-
Gap than other signals	2xwidth	-	-

• Keep analog TVOUT signal far from noise signals

I2C Interface

Schematics

• Predispose properly pullup resistors on line in accordance with DAVE Embedded Systems system-on-modules (SOM)
• Do not overload I2C lines with too much devices
• Ensure that I2C devices are being properly initialized during power up

PCB

• Isolate I2C clock from noise sensitive signals
• Avoid stub

SD/MMC Interface

	Min	Typ	Max
Common Mode impedance SOM(ohm)	-	50	60
Matching required*	-	-	-
Max allowed parallel routing(mils)	-	-	1000
Max trace Length**	-	-	-
Max # of vias allowed	-	-	-

*This is not mandatory, however it is suggested in case trace length exceeds 10cm

**Overall trace length - i.e. Bora + carrier board - should not exceed 10cm. If this is not possible, try to avoid parallel routing in order to reduce crosstalk, and refer them to a ground plane.

CAN Interface

	Min	Typ	Max
Differential Mode impedance(ohm)	108	120	132
Matching required	-	-	-
Min Interpair spacing	-	4xgap	-
Max allowed parallel routing(mils)	-	-	-
Max trace Length	-	-	-
Max via allowed	-	-	-

Functional guidelines

Sudden power off management

From the architectural standpoint, modern embedded systems often resemble traditional PCs. For example:

• they implement a rich set of I/O interfaces (large displays, Ethernet ports, USB ports, SDIO sockets etc.)
• they likely run complex operating systems that derive from desktop world (linux, Android, Windows CE etc.)
• they implement complex storage schemes (raw NAND, SSD, eMMC etc.).

One of the main difference between such systems and PCs is that the formers are - if appropriately designed - inherently resilient to sudden power fails. In any case, system designer should take into account these events and decide if and how manage them explicitly. Here are some typical techniques used to deal with this situation:

• in case the system is used by human operators, the use of clean shutdown - triggered by the user himself - should be encouraged to prevent sudden power off. Technically speaking, this can be done via GUI (soft button) or mechanical device (push buttons and alike). In the latter case, push button controllers such as Linear LTC2954 can be very useful to implement this feature
• in case no human operators interact with the system, more complex solutions might be required. This strategy is strongly dependent on hardware characteristics of SOM and must be approached on a case-by-case basis.

Thermal Management

Heat is generated by all semiconductors while operating and it is dissipated into the surrounding environment. This amount of heat is a function of the power consumed and the thermal resistance of the device package. Every silicon device on an electronic board must work within the limits of its operating temperature parameters (eg, the junction temperature) as specified by the silicon vendor.

Failure to maintain the temperature within safe ranges reduces operating lifetime, reliability, and performances and may cause irreversible damage to the system. Therefore, the product design cycle should include thermal analysis to verify that the device works within its functional limits. If the temperature is too high, component or system-level thermal enhancements are required to dissipate the heat from the system.

For detailed information, please refer to the following documents:

• Thermal management (Naon)
• AM335x Thermal Considerations

Integration guide

This page provides useful information and resources to system designers in order to quickly integrate ETRA in his/her application. This information complements SoM-independent recommendations provided on the Carrier board design guidelines (SOM) page.

Several topics are covered, ranging from hardware issues to manufacturing aspects.

Bootstrap configuration

For ETRA SOM, please refer to this section.

Power management

Default power management schemes may not be suited for the specific application. That's why it is strongly suggested to verify if it is needed to change it. For more details please refer to this page.

Internal routing information

Section not completed yet

A spreadsheet is available for download at this link containing detailed information about ETRA routing. This information should be used to check the nets matching of the overall system (carrier board + SOM).

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Interfaces and Connectors

Power Supply

The power supply for this EVB can be provided through J1 connector or from USB OTG connector.

Description

Power can be provided through the J1 connector. Power voltage range is +[12-24 V].

J1 is a two pins MSTBA 2.5/2-G-5.08 Phoenix connector.

Power Supply connector

Signals

The following table describes the interface signals:

Pin#	Pin function	Pin Notes
1	VIN	+[12-24 V]
2	GND	Ground

Power LED

DL1 is a green LED (placed near the SOM) it shows the status of the power input. This LED is ON when a valid power supply is present either from J1 or USB OTG port.

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CPU connector

Description

J18 is the 204-pin SODIMM connector of the ETRA SOM.

In this SBC design, the SOM is embedded in the carrier board so the connector is not actually usable but represents the SOM J1 connector.

For a detailed description of the SOM pinout, please refer to the ETRA SOM Hardware Manual SO-DIMM connector.

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JTAG interface

Description

The JTAG interface is available on the Evaluation Kit at the connector J11.

J11 is a 30 pin (2x15x2.54mm) header connector and is also used for expansion signlas.

JTAG connector

Signals

The following table describes the interface signals on J11 connector:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
17	J18.62	VDD	VDD	reference voltage
19	J18.90	JTMS-SWDIO	JTMS-SWDIO
21	J18.98	JTCK-SWCLK	JTCK-SWCLK
23	J18.92	JTDI	JTDI
25	J18.96	JTDO-TRACESWOO	JTDO-TRACESWOO
27	J18.94	NJTRST	NJTRST

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Ethernet interface

Description

The Ethernet interface is available on the Evaluation Kit at the connector J5.

J5 is a standard RJ45 connector connected to the SOM integrated ethernet controller and PHY.

J6 and J7 connectors are pin-to-pin compatible mounting options for the same interface.

Ethernet connector

Signals

The following table describes the interface signals on J18 SOM connector:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
3	J18.19	ETH_TX_P	Transmit data +
5	J18.21	ETH_TX_M	Transmit data -
6	J18.23	ETH_RX_P	Receive data +
8	J18.25	ETH_RX_M	Receive data -
2,11	J18.13	ETH1_LED	Eth link or activity led

Device mapping

This network interface is mapped at eth0 device in Linux.

Device usage

The peripheral is used the standard kernel interface and network protocol stack.

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Console interface

Description

The Console interface available on the Evaluation Kit at the connector J2.

J2 is a 4 pin (4x1x2.54mm) header connector for the two-wires USART1 port, used for debug purposes (bootloader and operating system serial console).

Console connector

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	J18.187	UART TX	Transmit line
2	J18.189	UART RX	Receive line
3	-	3V3_CB	Power output	This pin can be used to power an RS232 transceiver
4	-	DGND	Ground

Device mapping

USART1 is mapped to /dev/ttySTM0 device in Linux. The peripheral is used as the default serial console, both for the bootloader and the kernel.

Device usage

To connect to the debug serial port:

1. connect the UART to USB transceiver to J2 connector
2. start your favorite terminal emulator software on PC (eg: PuTTY); communication parameters are: 115200,N,8,1

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LCD interface

Description

The LCD interface available on the Evaluation Kit at the connector J13.

J13 si a 40-pin, 0.5mm pitch, ZIF connector that provides the following signals:

• 18-bit RGB interface
• DE and CLK control signals
• 3.3V power for logic
• 5V power for backlight
• PWM for backlight

LCD connector

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1,2,10,11,12,16,20,24,28,32,36,37,39,40	-	GND	Ground
3	J18.46	LCD_PWM	PWM for backlight
4,5,6	-	LCD_5V	5V for LED	this rail is enabled by the CPU via GPIO
7,8	-	LCD_VDD	3.3V for logic	this rail is enabled by the CPU via GPIO
9	J18.124	LCD_DE	LCD_DATA_ENABLE
13	J18.144	LCD_B7	LCD_B7 (MSB)
14	J18.142	LCD_B6	LCD_B6
15	J18.140	LCD_B5	LCD_B5
17	J18.138	LCD_B4	LCD_B4
18	J18.136	LCD_B3	LCD_B3
19	J18.134	LCD_B2	LCD_B2 (LSB)
21	J18.158	LCD_G7	LCD_G7 (MSB)	the use of this pin prevents the use of eMMC with 8bit bus
22	J18.156	LCD_G6	LCD_G6
23	J18.154	LCD_G5	LCD_G5
25	J18.152	LCD_G4	LCD_G4
26	J18.150	LCD_G3	LCD_G3
27	J18.148	LCD_G2	LCD_G2 (LSB)
29	J18.172	LCD_R7	LCD_R7 (MSB)
30	J18.170	LCD_R6	LCD_R6
31	J18.168	LCD_R5	LCD_R5
33	J18.166	LCD_R4	LCD_R4
34	J18.162	LCD_R3	LCD_R3
35	J18.160	LCD_R2	LCD_R2 (LSB)
38	J18.132	LCD_CLK	LCD_CLOCK

Device mapping

LCD is mapped to /dev/fb0 device in linux.

Device usage

The connector is pinout compatible with the Ampire AM-800480BTMQW-TBMH-A display.

WARNING: the use of the LCD peripheral prevents the use of the eMMC on board of the ETRA SOM as 8bit bus, only 4bit bus is available.

The periperal can be accessed by various linux packages as fbi (for simple image display), or more complex libraries as QT or gstreamer.

Alternate connector

The ETRA SBC provides a secondary LCD connector (not mounted by default) for the use of 24bit LCD interface.

Description

The 24-bit LCD interface can be available for the Evaluation Kit at the connector J14. For the use of this interface please send an e-mail to helpdesk@dave.eu

LCD connector - 24 bit RGB

J14 si a 40-pin, 0.5mm pitch, ZIF connector that provides the following signals:

• 24-bit RGB interface
• DE, CLK, HSYNC and VSYNC control signals
• 3.3V power for logic
• 5V power for backlight
• PWM for backlight
• two GPIO signals for panel configuration

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
9,18,27,36,40	-	GND	Ground
1,2	-	LCD_5V	5V for LED	this rail is enabled by the CPU via GPIO
3	J18.46	LCD_PWM	PWM for backlight
4	J18.58	LCD_5V_EN	LCD_5V power enable	can be used as GPIO if the 5V power switch is bypassed
5.6	-	LCD_VDD	3.3V for logic	this rail is enabled by the CPU via GPIO
7	-	LCD_DISP	pull-down (default)	can be statically configured with pull-up or pull-down
8	J18.124	LCD_DE	LCD_DATA_ENABLE
10	J18.144	LCD_B7	LCD_B7 (MSB)
11	J18.142	LCD_B6	LCD_B6
12	J18.140	LCD_B5	LCD_B5
13	J18.138	LCD_B4	LCD_B4
14	J18.136	LCD_B3	LCD_B3
15	J18.134	LCD_B2	LCD_B2
16	J18.176	LCD_B1	LCD_B1
17	J18.174	LCD_B0	LCD_B0 (LSB)	the use of this pin prevents the use of eMMC with 8bit bus
19	J18.158	LCD_G7	LCD_G7 (MSB)	the use of this pin prevents the use of eMMC with 8bit bus
20	J18.156	LCD_G6	LCD_G6
21	J18.154	LCD_G5	LCD_G5
22	J18.152	LCD_G4	LCD_G4
23	J18.150	LCD_G3	LCD_G3
24	J18.148	LCD_G2	LCD_G2
25	J18.180	LCD_G1	LCD_G1	the use of this pin prevents the use of uSD with 4bit bus
26	J18.178	LCD_G0	LCD_G0 (LSB)
28	J18.172	LCD_R7	LCD_R7 (MSB)
29	J18.170	LCD_R6	LCD_R6
30	J18.168	LCD_R5	LCD_R5
31	J18.166	LCD_R4	LCD_R4
32	J18.162	LCD_R3	LCD_R3
33	J18.160	LCD_R2	LCD_R2
34	J18.184	LCD_R1	LCD_R1	the use of this pin prevents the use of eMMC with 8bit bus
35	J18.182	LCD_R0	LCD_R0 (LSB)
37	J18.130	LCD_HSYNC	LCD_HORIZONTAL_SYNC	the use of this pin prevents the use of eMMC with 8bit bus
38	J18.132	LCD_CLK	LCD_CLOCK
39	J18.128	LCD_VSYNC	LCD_VERTICAL_SYNC

Device usage

WARNING: the use of the 24bit LCD peripheral prevents the use of the eMMC on board of the ETRA SOM as 8bit bus, only 4bit bus is available. It also prevents the use of uSD device as 4bit bus, only 1bit bus is available.

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MIPI interface

Description

The MIPI Display serial Interface interface available on the Evaluation Kit at the connector J19

J19 is a 10 pin ZIF connector (0.5mm pitch, bottom contacts) for the DSI interface.

MIPI connector

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	-	DGND	Ground
2	J18.121	DSI_D1P	data lane1 +
3	J18.119	DSI_D1N	data lane1 -
4	-	DGND	Ground
5	J18.117	DSI_D0P	data lane0 +
6	J18.115	DSI_D0N	data lane0 -
7	-	DGND	Ground
8	J18.113	DSI_CKP	clock +
9	J18.111	DSI_CKN	clock -
10	-	DGND	Ground

Device mapping

The MIPI CSI peripheral is mapped to the corresponding /dev/video<X> device in Linux. The device mapping depends on the device tree configuration.

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micro SD interface

Description

The micro SD interface available on the Evaluation Kit at the connector J4.

J4 is a Micro-SD card header. This interface is connected to the SDMMC1 controller of the STM32MP1 CPU.

micro SD connector

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	J18.79	PE6	Data 1
2	J18.81	PC11	Data 3
3	J18.83	PD2	CMD
4	-	3V3_SD	+3.3 V
5	J18.85	PC12	Clock
6, 10	-	DGND	Ground
7	J18.75	PC8	Data 0
8	J18.77	PC9	Data 1
11, 12, 13, 14	-	PCB_GND_RNG	Shield
9	J18.177	PE9	Card detect

Device mapping

The microSD card is mapped to /dev/mmcblk1. The available partitions are available as /dev/mmcblk1p8, /dev/mmcblk1p9, /dev/mmcblk1p10, etc.

Device usage

The device can be mounted/accessed as a standard block device in Linux.

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UARTs interface

Description

The UART interfaces are available on the Evaluation Kit at the connectors J9 and J10.

J9 and J10 are 3 pin terminal blocks 5.0mm pitch respectively for USART3 and UART8. Can be independently used as RS232 or RS485 based on Part Number composition.

UARTs connector

Signals

The following table describes the interface signals:

J9

Pin#	SOM Pin#	RS232	RS485	Pin Notes
1	J18.89	USART3_TX	RS485_A
2	J18.91	USART3_RX	RS485_B
3	-	Ground	Ground

J10

Pin#	SOM Pin#	RS232	RS485	Pin Notes
1	J18.191	UART8_TX	RS485_A
2	J18.193	UART8_RX	RS485_B
3	-	Ground	Ground

Device mapping

USART3 is mapped to /dev/ttySTM1 device in Linux.

UART8 is mapped to /dev/ttySTM2 device in Linux.

Device usage

Fix the signal cables to the terminal with a small flat screwdriver.

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USB ports

Description

ETRA SBC provides two USB ports, one HOST and one OTG:

• J17 is a standard USB HOST 2.0 Type A connector

USB HOST connector

• J16 is a micro-AB type receptacle for a USB OTG connection: this interface can operate in Host mode and Device (peripheral) mode

USB connector

Signals

The following table describes the interface signals:

USB HOST

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	J18.188	USB_HOST_VBUS	VBUS
2	J18.202	USB_DM1	USB Host Data -
3	J18.200	USB_DP1	USB Host Data +
4	-	DGND	Ground
5, 6, 7, 8	-	PCB_GND_RNG	Shield

USB OTG

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	J18.185	VBUS_OTG_IN	VBUS	Can be used to power the board
2	J18.196	USB_DM2	USB OTG Data -
3	J18.198	USB_DP2	USB OTG Data +
4	J18.72	PA8	USB OTG ID
5	-	GND	Ground
6, 7, 8	-	PCB_GND_RNG	Shield

Device mapping

The USB Host port can be used under Linux for connecting USB peripheral devices: the related peripheral driver has to be integrated into the Linux kernel.

The USB OTG feature can be easily tested using the Mass Storage Gadget driver.

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Touchscreen interface

Description

The Touchscreen interface is available on USB or I2C interface connectors.

ETRA Evaluation Kit uses, by default, the USB interface for connecting the touchscreen controller. Anyway, the I2C interface is available too and - optionally - can be activated in the device tree for enabling the I2C touch controller driver.

USB touchscreen

The USB OTG port - available on J16 connector - is configured as USB Host controller for driving the touchscreen. For this purpose, it is required to enable the USB OTG ID signals a low. This can be possible using the S1.4 DIP switch which forces the ID signal as low:

Touchscreen connector

USB OTG ID set to low

I2C touchscreen

The I2C touchscreen interface is available on the Evaluation Kit at the connector J20. J20 is a 6-pin Molex PicoBlade connector for the I2C and control signals needed by most of the capacitive TSC.

This interface can be configured to work with 3.3V (default) or 5V power and signal levels.

Touchscreen connector

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	-	DGND	Ground
2	J18.48	TOUCH_SDA	I2C_SDA
3	J18.38	TOUCH_SCL	I2C_SCL
4	J18.101	TOUCH_VDD	TSC power	powered through a control switch
5	J18.201	TOUCH_INT	TSC interrupt	input
6	J18.199	TOUCH_RES	TSC reset	output

Device mapping

The device is typically mapped to /dev/touchscreen0 device in Linux.

The touch controller is attached to the generic Linux input event interface (evdev).

Device usage

The simplest tools for touch screen management are the tslib library and ts_tools utilities. To calibrate the touch screen, the ts_calibrate command line tool is available. After calibration, the touch screen can be tested using the graphical ts_test utility or the ts_print command line tool.

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RTC device

Description

There are two RTC devices on the Evaluation Kit, one is provided by the STM32MP1 SoC, the other is a Maxim DS3232M I2C device.

Both RTC can retain time and custom data over blackouts using a backup power source as:

• the lithium rechargeable battery (BT1) optionally mounted on the carrier board
• an external battery connected to J3 (alternate mounting option to the battery)

BT1 or connector battery options

Signals

The following table describes the interface signals for J3:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1	J18.14	VBAT		can be configured for battery connection
2	-	DGND	Ground

Device mapping

RTC is mapped to /dev/rtc0 device in Linux.

Device usage

The peripheral can be accessed through the date and hwclock linux commands.

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Watchdog peripheral

Description

The Watchdog peripheral available on the Evaluation Kit is provided by the Maxim MAX6373.

The MAX6373 device has 3 configuration pins that allow to select the following:

• the startup delay from 3ms to 60s or first edge of the WDI signal
• the watchdog time (maximum time between WDI toggles) from 3ms to 10s or disable.

As default the device is configured for start the operations on first edge of the WDI signal with a timeout of 10s. For custom configurations please send an e-mail to helpdesk@dave.eu

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
U6.1	J18.28	WDI	Watchdog input
U6.7	J18.24	WDO	Watchdog output	system reset pin

Device usage

To use the watchdog device toggle the WDI pin at least once every 5 seconds.

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DWS

DWS is a Dave Wireless Module, more details at the DWS page.

Description

The DWS interface is available on the Evaluation Kit at the connector J8.

J8 is a 30-pins 0.50mm Pitch SlimStack™ Receptacle. This connector is dedicated to the DWS (optional) add-on module.

The module is built around a Telit WE866C6-P Dual Band (2.4GHz and 5GHz) 802.11 ac WiFi and Bluetooth 5 module.

The module implements the necessary PHY/MAC layers to support WLAN applications in conjunction with a host processor over a SDIO interface. The module also provides a Bluetooth platform through the HCI transport layer. Both WLAN and Bluetooth share the same antenna port.

DWS connector

DWS wifi module mounted on board

Signals

The following table describes the interface signals:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
1, 2	-	5V_CB	5V power
3, 4	-	3V3_CB	3.3V power
5, 6, 9, 10, 19	-	DGND	Ground
7	J18.45	WIFI_CMD
8	J18.47	WIFI_CLK
11	J18.37	WIFI_DATA0
13	J18.39	WIFI_DATA1
15	J18.41	WIFI_DATA2
17	J18.43	WIFI_DATA3
21	J18.80	BT_UART_RX		Used only for BT peripheral
23	J18.76	BT_UART_CTS		Used only for BT peripheral
24	J18.105	BT_F5
25	J18.74	BT_UART_TX		Used only for BT peripheral
26	J18.72	BT_F2
27	J18.78	BT_UART_RTS		Used only for BT peripheral
28	J18.70	IRQ
29	J18.51	BT_EN
30	J18.53	EN
12, 14, 16, 18, 20, 22	-	N.C.	Not connected

Device mapping

The WiFi peripheral is mapped to the corresponding wlan0 device in Linux. The network peripheral is visible under the ifconfig network configuration utility.

The BT peripheral is mapped to /dev/ttySTM3 device in Linux.

The control signals are managed by rfkill in Linux.

Device usage

The WiFi peripheral uses the standard kernel interface and network protocol stack.

The BT peripheral uses the standard kernel hci interface.

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GPIOs interface

Description

STM32MP1 can handle external pins in many different ways and most of them can be configured as GPIOs. When a pin is set as a GPIO, it is possible to read its value, change its direction or change output value directly from the shell.

GPIOsconnector

Signals

The following table describes some GPIOs signals available on J12 (2x15x2.54mm) connector:

Pin#	SOM Pin#	Pin name	Pin function	Pin Notes
3	J18.97	PD13
5	J18.99	PD12
6	J18.34	PB13
7	J18.101	PD11
8	J18.68	PB5
9	J18.105	PG9
12	J18.48	PA12
14	J18.38	PA11
18	J18.80	PF6
20	J18.76	PF9
22	J18.74	PF7
24	J18.78	PF8
26	J18.181	PD6
28	J18.28	PA9

Device mapping

GPIOs can be used directly on Linux kernel device driver or can be configured on the device tree.

Device usage

See the GPIOs page on the DESK-MP1-L Software Manual.

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Auxiliary connectors interface

Description

The Auxiliary connectors on the Evaluation Kit are J11 and J12, 2x15x2.54mm stripline header.

On these connectors are available many interfaces, some of this peripherals are not available at the same time:

• FDCAN1
• FDCAN2
• I2C5
• SPI5
• UART7
• SAI2
• 11x8 keyboard matrix
• LED driver
• JTAG

Auxiliary connectors

Signals

The following tables describe the connectors signals:

• J11

Pin#	SOM Pin#	Pin name	POWER	JTAG	KEYBOARD	LED
1	-	5V_CB	5V
2	-	3V3_CB	3.3V
3	J18.143	ADP5589_R2			ROW_2
4	J18.149	ADP5589_C0			COLUMN_0	LED_0
5	J18.141	ADP5589_R3			ROW_3
6	J18.151	ADP5589_C1			COLUMN_1	LED_1
7	J18.139	ADP5589_R4			ROW_4
8	J18.155	ADP5589_C2			COLUMN_2	LED_2
9	J18.137	ADP5589_R5			ROW_5
10	J18.157	ADP5589_C3			COLUMN_3	LED_3
11	J18.135	ADP5589_R6			ROW_6
12	J18.159	ADP5589_C4			COLUMN_4	LED_4
13	J18.133	ADP5589_R7			ROW_7
14	J18.161	ADP5589_C5			COLUMN_5	LED_5
15,20,29	-	DGND	Ground
16	J18.147	ADP5589_R0			ROW_0
17	-	VDD	3.3V	ref. voltage
18	J18.145	ADP5589_R1			ROW_1
19	J18.90	JTMS-SWDIO		JTMS-SWDIO
21	J18.98	JTCK-SWCLK		JTCK-SWCLK
22	J18.163	ADP5589_C6			COLUMN_6
23	J18.92	JTDI		JTDI
24	J18.165	ADP5589_C7			COLUMN_7
25	J18.96	JTDO-TRACESWOO		JTDO-TRACESWOO
26	J18.167	ADP5589_C8			COLUMN_8
27	J18.94	NJTRST		NJTRST
28	J18.169	ADP5589_C9			COLUMN_9
30	J18.171	ADP5589_C10			COLUMN_10

• J12

Pin#	SOM Pin#	Pin name	POWER	System control	CAN	I2C	SPI	UART	SAI
1	-	5V_CB	5V
2,4	-	PMIC_3V3	3.3V
3	J18.	PD13							SAI2_SCK_A
5	J18.	PD12							SAI2_FS_A
6	J18.	PB13			FDCAN2_TX
7	J18.	PD11							SAI2_SD_A
8	J18.	PB5			FDCAN2_RX
9	J18.	PG9							SAI2_FS_B
10, 11, 16, 19, 29, 30	-	DGND	Ground
12	J18.	PA12			FDCAN1_TX	I2C5_SDA
13	-	3V3_CB	3.3V
14	J18.	PA11			FDCAN1_RX	I2C5_SCL
15	-	N.C.
17	-	N.C.
18	J18.	PF6					SPI5_NSS	UART7_RX
20	J18.	PF9					SPI5_MOSI	UART7_CTS
21	J18.	NRST		system reset
22	J18.	PF7					SPI5_SCK	UART7_TX
23	J18.	PONKEYn		power key
24	J18.	PF8					SPI5_MISO	UART7_RTS/ UART7_DE
25	J18.	EEPROM_WP		write protect for carrier eeprom
26	J18.	PD6
27	J18.	MEM_WP#		write protect for NAND
28	J18.	PA9

Device usage

CAN

The CAN interfaces need a tranceiver to be connected to the CAN bus.

NOTE: the FDCAN1 pins are shared with touchscreen I2C interface and are not available when using I2C5.

See the CAN page for more informations.

I2C5

Configured by deafult for touchscreen I2C interface.

See the I2C page for more informations.

SPI5

NOTE: these pins are shared with UART7, cannot be used at the same time.

See the SPI page for more informations.

UART7

NOTE: these pins are shared with SPI5, cannot be used at the same time.

See the UART page for more informations.

SAI2

See the Audio page for more informations.

LED driver

Open collector outputs through a 120ohm resistor. Can be drive indicators LEDs

By default all the pins are available.

keyboard matrix

NOTE: COLUMN[0:5] are not available by default as the pins are routed to the LED open collector outputs. Please send an e-mail to helpdesk@dave.eu for custom configurations.

See the IO_expander page for more informations.

Interface membrane

This mambrane can be provided for user interface when the system is mounted on the 4 modules DIN BAR profile, it can offer up to 2 keys and 6 LEDs.

Please send an e-mail to helpdesk@dave.eu for more informations.

JTAG

See the JTAG page for more informations.

System control

See the reset scheme for more informations.

The system control signals are the following:

• system reset
  • tie to ground for reset the system
• power key
  • tie to ground for power up and down the system
• write protect for carrier eeprom
  • tie to ground for write inside the carrier eeprom
  • the first 32 bytes of the eeprom are used to store the CB ConfigID, the corruption of these bytes prevents the system from boot.
• write protect for NAND
  • this pin allow to prevent unwanted writes, tie to ground when the NAND are not to be written.

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Electrical and Mechanical Documents

Please find here below the links for the ETRA Evaluation Kit schematics and the related documents (BOM and layout).

Please note that SBC ETRA has been built around the ETRA SOM: on page 12 there is the SO-DIMM connector which separates the inside SOM core vs the external SBC. The SOM schematics are reserved and not published as documentation. Off-page numbers in the SO-DIMM connector greater than 12, are referring to the SOM schematics and so not present in the available schematic pages

Schematics

• PDF: ETRA EVK PDF schematics

Layout

• ETRA EVK Assembly view

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Mechanical specifications

This page describes the mechanical characteristics of the ETRA SBC board.

Board layout

Assembly view: top

Assembly view: bottom

Dimensions

Mechanical data

Dimension	Value
Width	87 mm
Depth	68 mm
Max component's height (top)	- mm
Max component's height (bottom)
PCB height	- mm

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