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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
Page 2 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�
SmartBoard Baseboard Instruction Guide
Page 4 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�
SmartBoard Baseboard Instruction Guide
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.
SmartBoard Baseboard Instruction Guide
Page 13 of 50 Revision: 9 September 2015
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.
SmartBoard Baseboard Instruction Guide
Page 14 of 50 Revision: 9 September 2015
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.
SmartBoard Baseboard Instruction Guide
Page 25 of 50 Revision: 9 September 2015
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
SmartBoard Baseboard Instruction Guide
Page 32 of 50 Revision: 9 September 2015
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.
SmartBoard Baseboard Instruction Guide
Page 35 of 50 Revision: 9 September 2015
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
SmartBoard Baseboard Instruction Guide
Page 40 of 50 Revision: 9 September 2015
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
SmartBoard Baseboard Instruction Guide
Page 43 of 50 Revision: 9 September 2015
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.