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Figure 1 SmartBoard Baseboard

1 SmartBoard Baseboard v1.01

This document is a design and usage guide for integrating the NXP LP1768 mbed

into various applications using the SmartBoard Baseboard.

The virtual image shown in Figure 1 is actually from a prior revision of the

design. While retaining the same overall footprint, additional flexibility is

available in version 1.01, documented here.

Board Revision: v1.01

Document Revision: v1.02

SmartBoard Baseboard Instruction Guide

of 50 Revision: 9 September 2015

2 Table of Contents

2.1 Sections

1� SmartBoard Baseboard v1.01 .................................................................................................1�2� Table of Contents ...................................................................................................................3�

2.1� Sections ............................................................................................................................ 3�2.2� Figures .............................................................................................................................. 4�

3� Introduction ............................................................................................................................6�3.1� Design Objectives ............................................................................................................ 6�3.2� The mbed .......................................................................................................................... 6�3.3� Cautions ............................................................................................................................ 6�

4� Mechanical Interfacing ...........................................................................................................8�5� Circuit Assembly ..................................................................................................................10�

5.1.1� Surface Mount Parts ................................................................................................ 10�5.1.2� Alternate Parts ......................................................................................................... 10�

6� Construction .........................................................................................................................11�6.1� Errata .............................................................................................................................. 11�6.2� Construction Recommended Procedure ......................................................................... 12�6.3� Board Electrical Check................................................................................................... 20�

7� Configuration .......................................................................................................................22�8� Electrical Interfacing ............................................................................................................25�

8.1� Power Inputs ................................................................................................................... 25�8.1.1� USB Powered .......................................................................................................... 25�8.1.2� External +12v Power Source .................................................................................. 25�8.1.3� 5v Regulator Options .............................................................................................. 25�

8.2� Battery Backup ............................................................................................................... 26�8.3� Micro SD ........................................................................................................................ 26�8.4� Ethernet .......................................................................................................................... 26�

8.4.1� LEDs ....................................................................................................................... 27�8.5� USB-Host ....................................................................................................................... 27�8.6� USB-Peripheral .............................................................................................................. 27�8.7� PWM Output .................................................................................................................. 27�8.8� Analog Input ................................................................................................................... 27�

8.8.1� Accuracy ................................................................................................................. 28�8.8.2� Frequency Response ............................................................................................... 29�

8.9� Analog Output ................................................................................................................ 30�

8.10� Serial Channel(s) 1 and 2 ............................................................................................ 30�8.10.1� RS-232 Channels ................................................................................................. 30�

8.11� Serial Channel 3.......................................................................................................... 31�8.12� I

2C Channel 2.............................................................................................................. 31�

8.13� SPI Channel 1 ............................................................................................................. 31�8.13.1� Micro SD ............................................................................................................. 31�8.13.2� SPI Channel 1 Port 2 ........................................................................................... 32�

8.14� CAN Channel(s) ......................................................................................................... 32�8.15� Figure 12 CAN Network ............................................................................................ 32�

8.15.1� CAN Channel 2 ................................................................................................... 32�8.15.2� CAN Channel 1 ................................................................................................... 33�

9� Software ...............................................................................................................................34�9.1� Test Software.................................................................................................................. 34�

10� Bill of Materials ...................................................................................................................35�


of 50 Revision: 9 September 2015

10.1� BOM Notes – Retrospect ............................................................................................ 37�10.2� Optional and Alternate Parts ....................................................................................... 38�

11� Application Examples ..........................................................................................................40�11.1� Couch Calendar .......................................................................................................... 40�11.2� X10 Server .................................................................................................................. 41�11.3� Wireless Interface ....................................................................................................... 42�11.4� CEC Control Interface ................................................................................................ 43�11.5� Energy Monitor........................................................................................................... 44�11.6� Other Ideas .................................................................................................................. 46�

12� SmartBoard Baseboard Schematic .......................................................................................47�13� SmartBoard Baseboard PCB Layout ....................................................................................48�14� Links and References ...........................................................................................................50�

2.2 Figures

Figure 1 SmartBoard Baseboard ..................................................................................................... 1�Figure 2 Mechanical and Connectors ............................................................................................. 8�Figure 3 v1.01 PCB Modification ................................................................................................. 11�Figure 4 Bare PCB Top-side ......................................................................................................... 20�Figure 5 Shunts Installed for Testing ............................................................................................ 21�Figure 6 Jumper Configuration ..................................................................................................... 22�Figure 7 Header Locations ............................................................................................................ 23�Figure 8 Analog Input ................................................................................................................... 28�Figure 9 Ratio Metric Sensing ...................................................................................................... 29�Figure 10 DB9 Interface ............................................................................................................... 30�Figure 11 Serial Channel on DB-9................................................................................................ 31�8.15� Figure 12 CAN Network ................................................................................................... 32�Figure 13 Couch Calendar Display ............................................................................................... 40�Figure 14 Couch Calendar Backside ............................................................................................. 40�Figure 15 X10 Devices ................................................................................................................. 41�Figure 16 X10 Server Components............................................................................................... 42�Figure 17 X10 Sample Web Interface .......................................................................................... 42�Figure 18 Wifly Module Stackup ................................................................................................. 43�Figure 19 CEC Interface ............................................................................................................... 44�

Figure 20 Utility Meter with Spinning Disk ................................................................................. 44�Figure 21 Digital Utility Meter ..................................................................................................... 45�Figure 22 Couch Calendar Energy Data ....................................................................................... 45�


Page 10 of 50 Revision: 9 September 2015

5 Circuit Assembly

There is very little that is critical about assembling the components onto the PCB,

however this section does provide a few guiding elements.

Where practical, all parts are through-hole parts for ease of assembly – this

includes the component installation, as well as ease of soldering. This also eases

the effort should there be a need for rework.

5.1.1 Surface Mount Parts

Among the surface mount parts are the analog input protection diodes and the

micro SD card socket.

5.1.2 Alternate Parts

The flexibility of this design includes some capability for alternate parts. This

section calls out the alternates.

The serial RS-232 channel using a fairly large DB-9 connector may be left out,

and instead combinations of two other screw terminal connectors may be

installed. This grants access to two serial ports. Of these two serial ports, one is

RS-232, and the other can be RS-232 or I2C channel 2.



The smallest, and most challenging to solder, parts are first.

SUGGESTION: Clean your iron, workspace, and practice your fine-pitch

soldering on a scrap project before starting here.

D2, D4, D6

Install three diodes in the lower left

corner of the top-side.

CAUTION: These parts look nearly

identical to D8 and D9. Take care not to

confuse them.

NOTE: D3, D5, and D7 will be installed

on the bottom. Save this step for nearly

the last, to keep the PCB stable on your

workbench.

SD1

Install the surface mount connector for the micro SD card. This

will be the most difficult installation due to the fine-pitch spacing

and the position of the leads in the housing.

Note that there are two layouts

over top of each other, permitting

the use of either of two

connectors.

Careful visual inspection is

recommended following the

installation.

IC3, IC4, IC5 Install each of these sockets, noting the orientation is to the top

for IC3 and IC4 sockets and to the left for IC5.



X1, X2, X7,

X8

Install the terminal strips. This combination, when installed,

keeps the PCB stable when you turn it upside down.

X4, X5, or

X6

The design permits use of either a pair of screw terminals or the

use of a DB-9 connector. Install whichever is appropriate for the

need. This may also be deferred to later.

BAT1 Prior to installing the battery holder itself,

place a thin layer of solder on the large

square pad in the center. Inspect this layer

to ensure it is smooth and thin. Remove

any excess and reheat to smooth it out if

necessary. This thin layer ensures good

contact with the battery when installed.

Next, install the socket.



8 Electrical Interfacing

8.1 Power Inputs

There’s quite a bit to look at with respect to the power supply circuitry.

Depending on the needs, there are several ways to get power to the mbed. This

section goes into that detail.

8.1.1 USB Powered

The breakout board is capable of being configured to operate solely from the USB

connector on the mbed itself. Simply plug a USB cable into the host PC and the

USB-B connector on the mbed itself. For more demanding applications, an

external power supply will be needed.

8.1.2 External +12v Power Source

A voltage between about 6 or 7 and up toward 26 to 36 can be connected on either

the CAN 1 or CAN 2 connector – depending on which regulator is selected as

shown below. Pin 2 on each CAN connect is tied to the +12v line and from there

it is reverse protected where it connects to the 3 terminal regulator. Depending on

the needs, it is possible to feed 12v into one of these pins and draw 12v from the

other for external circuitry (to avoid harness splicing). The PCB design should be

able to carry a few amps between these two connectors.

NOTE: If CAN is not needed, a 2-pin connector could be installed instead of the

4-pin – just use the Pin1 and 2 positions. This reduces the possibility of mis-

wiring, and can lower the cost a small amount if a number of the same device is

being built.

8.1.3 5v Regulator Options

If the device will not source power to any external circuitry, or if that power

demand is very low, then it may be practical to omit the regulator. Note that the

mbed can draw its power from this regulator, as may be typical in an embedded

(not PC connected) application.

8.1.3.1 5v Regulator – Low Current/Low Noise

For low power applications, a simple linear 5v regulator can be sufficient. This

may also be appropriate if for designs reading sensitive analog signals. But do

note that with a single ground on the mbed part, supporting both the analog and

digital circuits; this can couple noise which affects the quality of the analog

inputs. The TI TL750M05CKCSE3 is an inexpensive low dropout regulator in a

TO-220 package. This part is rated to deliver up to 750 mA, if the power can be

managed. The input voltage range is from 6 to 26. Add an additional 0.6v for the

reverse protection diode. This part is likely to exceed the power dissipation rating

at 26v unless properly managed.

NOTE: In some applications, this part may get hot, and it may be

appropriate to provide external heat-sinking. The TO-220 tab faces



8.13.2 SPI Channel 1 Port 2

SPI Channel 1 can also be accessed on X2. Take care in software so that this port

and the micro SD are used mutually exclusively.

Also, external hardware can be powered from this board at either 5v or 3.3v

depending on the JP1 configuration.

8.14 CAN Channel(s) Controller Area Network (CAN) is a popular communication network on modern

cars, trucks, boats, industrial systems, hospital beds, and more. Unlike RS-232,

USB, and Ethernet, CAN can be multi-drop, as seen in Figure 12. Depending on

the specific transceiver capabilities, there can be from 2 to 20, or even 30 or more

nodes on one single pair of wires. It is common to use twisted pair for improved

noise margin.

Typical data rates for CAN range from 20 kbits/sec up to 1 megabits/sec. A

longer network typically is configured for a slower data rate.

A CAN-based network has other attributes that make it both reliable and robust.

Search online for one of the many tutorials and to understand the characteristics

of CAN.

8.15 Figure 12 CAN Network This design supports up to 2 channels of CAN communications.

Important to a CAN network are the terminating resistors. As shown in Figure 12

there is one in each module at the “geographic end” of the network. The

module(s) in the middle should not have the termination. Too many terminators

will reduce the design margin and signal quality.

While locations on the PCB support installation of termination resistors, the best-

practice is to put them in the harness. In this way, any one board could be

swapped for another without having to do the surgery to add or remove the PCB

based termination.

8.15.1 CAN Channel 2

CAN channel 2 is available on connector X7.



10 Bill of Materials

Following is the bill of materials for a single kit. Refer to this during assembly to

quickly identify a part. Note, however, that parts are not shown to scale. The last

column shows the Digi-Key part numbers.

Qty. Image Reference Description D.K. Part #

1

X1 TERM BLOCK 3.5MM

VERT 2POS PCB

ED2635-ND

1

X4 TERM BLOCK 3.5MM

VERT 3POS PCB

ED2636-ND

3

X5, X7, X8 TERM BLOCK 3.5MM

VERT 4POS PCB

ED2637-ND

1

X2 TERM BLOCK 3.5MM

VERT 6POS PCB

ED2639-ND

1

X1 TERM BLOCK 3.5MM

VERT 8POS PCB

ED2641-ND

1

BAT1 HOLDER BATTERY COIN

12MM DIA THM

3001K-ND

2

IC1 DUAL ROW SOCKET

CONN HEADR FMALE

40POS .1" DL AU

S9200-ND

1

IC5 IC SOCKET STRAIGHT

16POS TIN

AE9992-ND

2

IC3, IC4 IC SOCKET STRAIGHT

8POS TIN

AE9986-ND

13

JP1, JP2, JP5,

JP6, JP7, JP8,

JP10,

PW1, PW2,

PW3, PW4,

PW5, PW6

SIL VERTICAL PC TAIL

PIN HEADER

952-2264-

ND



11 Application Examples

11.1 Couch Calendar The Couch Calendar is a concept for a small display, much like the “photo frame”

appliances. In this case, it draws calendar events from an account on a WebDAV

server in the iCal format. It also syncs its clock to a stable network time protocol

source. As a convenience, it shows a few weather related items – outside

temperature, humidity, and wind direction and speed.

Figure 13 Couch Calendar Display

Tipped forward, the stack of components is visible. From the bottom up is the

display module, a piece of perf-board as a mechanical mount for the SmartBoard,

upon which is the mbed module. This system receives power via the USB

interface on the mbed, and its information source comes via Ethernet.

Figure 14 Couch Calendar Backside



Figure 18 Wifly Module Stackup

This shows a Wifly module plugged in to a SmartBoard Wifly adapter. That in

turn bridges over the mbed module down to the SmartBoard Baseboard.

11.4 CEC Control Interface This module is another “bridge board” design that straddles over top of the mbed

module. Visible is the HDMI connector. The only signal used on this connector is

the 1-wire CEC communication signal. This signal is traveling along with the

video signals, but is a low power and slow signal used to turn devices on and off,

change the channel and volume, select input sources and so on.

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