BHI NEDSP1061-PCB Installation And Operating Manual

Page 1

bhibhi

bhibhi

bhi

NEDSP1061-PCB

Noise Eliminating Modules

Installation and

Operating Manual

1061-108D

Issue C

DSP Noise Cancelling Products

Page 24

bhi ltd

PO Box 318

Burgess Hill

West Sussex

RH15 9NR

tel: [phone]

fax: [phone]

[e-mail]

www.bhi-ltd.com

bhibhi

bhibhi

bhi

DSP Noise Cancelling Product s

Page 2

Important Information

Copyright

This publication, including all photographs and
illustrations is protected under international
copyright laws, with all rights reserved. Neither
this manual, nor any of the material within, may
be copied or reproduced without the written
consent of bhi Ltd.

Disclaimer

The information in this document is subject to
change without notice. bhi Ltd. makes no
representations or warranties with respect to the
contents hereof and specifically disclaims any
implied warranties of merchantability or fitness for
any particular purpose. Furthermore, bhi Ltd.
reserves the right to revise this publication and to
make changes from time to time in the content
hereof without obligation of bhi Ltd. to notify any
person of such revision or changes.

Page 23

Notes:

Page 3

Contents

1. Introduction

1.1 NEDSP1061 features 4

1.2 Limitations 4

1.3 Module connection and mounting 5

1.4 DSP noise cancellation 6

2. Module description

2.1 Block diagram 7

2.2 Module layout 8

2.3 Pin functions 9

2.4 Controls 10

2.5 Electrical characteristics 10

3. Installation 11

4. Functions

4.1 Noise reduction levels 13

4.2 Pre-setting different DSP levels 13

4.3 Remote setting of DSP level 14

4.4 Noise cancellation on/off 15

5. Application notes

5.1 Noise cancellation indication 16

5.2 Remote adjustment of level 17

5.3 Driving a low impedance load 19

5.4 Audio bypass 19

Index 20

Page 22

Notes:

Page 4

1. Introduction

The NEDSP1061 is a modular solution to noise reduction.
It incorporates DSP technology to provide up to 35dB of
noise cancellation.

1.1 NEDSP1061 module features:

 Fully adaptive to changing noise environments
 Input and output level controls
 Virtually no distortion to speech signal
 Up to 35dB of noise cancellation
 8 levels of noise reduction
 Noise cancellation can be preset or remotely set

during operation

 5 – 15V supply range
 4.6dB on board gain
 Wide range of connection possibilities
 Mounting holes

1.2 Limitations.

This module is designed to pass speech. Other signals
such as data, music and morse (CW) will to some degree
pass through, but the integrity of these signals
cannot be guaranteed.

This module is designed to be placed in a low level audio
path only. The module will not drive a loudspeaker or
other high power load.

Page 21

Notes:

Page 5

Plug in Vertically

Plug in Horizontally

Horizontal connector

Figure 1. Connection options

1.3 Module connection and mounting

Connections to the module are made by a row of 10
pads at the right hand side of the PCB. These pads are
on a 2.54mm (0.1”) pitch, which allows the use of
standard pin headers, PCB connectors and direct wiring.

Vertical mounting.

Use a 10 way 0.1” pitch right
angled pin header in the PCB
(J2). The module can then plug
into a suitable mating connector,
or be soldered directly to the
target system.

Horizontal mounting.

Use a 10 way 0.1” pitch straight
pin header in PCB (J2). Mount a
4 way header in the PCB (J1).
Do not connect these pins to the
circuit, use them purely for
mechanical fixing.

Other options.

Use a right angled pin header to
mate with a 10 way wired
connector.
Wire the PCB directly and mount
using the four fixing holes.

Page 20

Index

A

Application Notes 16
Audio bypass 19
Audio input. 9
Audio out 9

B

Buffered output stage 19

C

Copyright 2

D

Disclaimer 2
Driving a low impedance load 19
DSP filter level set 9

E

Electrical characeristics 10

I

Important Information 2
inhibit noise cancellation, 15

M

microcontroller. 18

N

Noise Cancellation On/Off 15
Noise cancellation on/off 9
Noise cancellation On/Off indication 16
Noise reduction levels 13
noisy audio 11

R

Remote adjustment of noise cancellation level. 17
Remote setting of DSP filter level 14
Remote setting of the DSP 14

S

safety critical 19
Setting different filter levels 13
Supply voltage 9

T

tricolour LED 16

Page 6

1.4 DSP Noise cancellation.

The bhi DSP processes the incoming signal and then
differentiates the speech from the noise. The unwanted
noise and interference is then attenuated to leave only
the speech.

The following diagrams are taken from actual audio
signals and illustrate how the signal is being processed.

Figure 1. Noise cancellation.

Original signal.

Speech with a lot of
background noise

Processed speech.

Speech with reduced
noise

Speech Noise

Reduced noise

Page 19

NEDSP 1061

Audio out

10

0V

7

-

+

+V

R1

10K

R2

10K

Buffered
Audio out

Bias to 1/2

off supply voltage

or use dual polarity

power supply

Figure 12. Buffered output stage.

5.3 Driving a low impedance load.

If the target system loads the output of the DSP module
it may necessary to buffer the output. This can be
achieved with a single op amp.

10

7

9

NEDSP 1061

Audio out

Audio In

0V

+V

5

Audio out

Audio in

Relay

Contacts

Power

off/bypass

switch

Vin

Relay

Coil

Protection

Diode

Figure 13. Audio bypass.

5.4 Audio Bypass.

In safety critical applications a bypass should be included
to maintain communications in the unlikely event of the
NEDSP1061 or the power failing. The following circuit
uses a relay to route the audio signal. In the even of
power failure to the module the relay will de-energise
and connect the input to output. Also shown is a switch
to bypass the module manually.

Page 7

2. Module description

Figure 2. NEDSP1061 block diagram

Output level

set

Input level

set

Analogue to

Digital conversion

Digital to analogue

conversion

BCD

DSP level select

Xtal

Clock generator

On Board

Jumpers

DSP core

10

9

1

2

3

8

7

3.3V

3.3V regulator

Polarity

protection

PCB

Connections

Internal

pull up

resistors

N0

N1

Vin

0V

N2

Noff

In

Out

5

2.1 Block diagram.

The NESDP1061 module has the facility to be preset, or
adjusted during operation. Digital inputs control the
functions. These incorporate internal pull up resistors,
so they can be left floating when not in use.

The audio signals into and out of the module are capacitor
coupled.

The on board voltage regulator allows the module to be
used with a wide range of input voltages, but to keep the
power dissipation (and heat) down it is advisable to use
as low as possible supply voltage. The power supply
input is reverse polarity protected.

Page 18

NEDSP 1061

N0

1

N1

2

N2

3

0V

7

micro controller

Figure 10. Control using a microcontroller

The module can be controlled with a microcontroller. As
the DSP employs internal pull ups, it is not necessary to
drive the microcontroller port pins high, they can be
placed in a high impedance state.

NEDSP 1061

N0

1

N1

2

N2

3

micro controller

a
b
c
d
e
f
g

display

BCD to

7 segment

decoder
CD4511

A
B
C

0V

Seven segment LED

display showing

DSP filter level

(note: displays 0 - 7)

Keyboard

Noff

8

Figure 11. Control using a microcontroller with display
and keyboard.

The following example employs a 7 segment display and
keyboard. Noise on/off is also controlled by the
microcontroller. In the diagram 3 buttons are used, up
level, down level and DSP on/off.

Page 8

++

1

2

3

4

5

6

7

8

9

10

JP3

JP1

JP2

Connections

Do not

Connect

these

pins

Mounting

holes
(4 off)

Input
level

Output

level

Noise cancellation

level jumpers

Top

Figure 3. NEDSP1061 connections and controls

2.2 Module Layout.

The following diagram shows the layout of the
NEDSP1061 module.

.oNniP emaN noitpircseD

1

0NtibnoitallecnacesionbslDCB

2

1NtibnoitallecnacesionDCB

3

2NBSMnoitallecnacesionDCB

4

C/Ntcennocto

noD

5

niVegatlovylppuS

6

C/NtcennoctonoD

7

V0noitcennocV0

8

ffoNnipffo/nonoitallecnacesioN

9

nItupnioiduA

01

tuOtuptuoo

iduA

Table 1. NEDSP1061 connection functions

Page 17

5.2 Remote adjustment of noise cancellation
level.

NEDSP 1061

N0

1

N1

2

N2

3

0V

7

0V

C

124

BCD

Complement

switch

This page illustrates various options for altering the DSP
level remotely, during operation.

Figure 8. Basic setting using a BCD switch

NEDSP 1061

N0

1

N1

2

N2

3

0V

7

124

0V

Note:

Inputs

will be inverted

N0

N1

N2

Figure 9. Basic setting using transistors

The transistors allow interfacing
with higher voltages to control the
DSP level. These could be
replaced by opto couplers for
greater isolation.

Page 9

2.3 Pin functions.

The basic operation of the NEDSP pins are described
below. More detailed descriptions can be found later in
this manual.

Pins 1-3 DSP filter level set.

These pins allow remote setting of the noise cancellation
level. If these pins are used, then remove the preset
jumpers JP1 - JP3 from the PCB.

Pin 5. Supply voltage.

Supply voltage 5-15VDC

Pin 7 0V

0V pin.

Pin 8 Noise cancellation on/off

Connecting this pin to 0V inhibits the noise cancellation.
Leave this pin floating to enable noise cancellation.

Pin 9 Audio input.

Audio signal to be processed.

Pin 10 Audio out

DSP processed signal out from the module.
For optimum performance, keep all leads as short as

possible. Use screened leads for the audio signal.

Page 16

5. Application Notes.

5.1 Noise cancellation On/Off indication.

Figure 7. Red/Green LED indication of noise cancellation.

In the above example a tricolour LED (or separate Red
and Green LEDs) are used to give a visual indication of
the noise cancellation mode. The green LED will
illuminate when the noise cancellation is on, and the red
when off.

NEDSP 1061

0V

7

Noff

8

+V

0V

Red Green

R1 R2

Noise

cancellation

Off

DPDT

switch

Page 10

2.4 Controls.

The audio level control potentiometers P1 (Audio out),
and P2 (Audio in) provide adjustment to the audio levels
entering and leaving the module.
P1 is factory set near to maximum.
T o set the input level correctly , adjust P2 until the
overload led D1 (next to P2) illuminates, then back off
the potentiometer approximately a 1/4 of a turn.
Turning the potentiometers anti clock wise will increase
the levels.

scitsiretcarahCeugolanA

retemaraP noitpircseD niM pyT xaM stinU

V

ni

egatlovylppuS5951V

I

ni

tnerrucylppuS5405Am

nIlangistupnioiduA05003smrV

tuO

langistuptuooiduA

)xamtupnisX7.1(

036smrV

scitsiretcarahClatigiD

retemaraP noitpircseD niM pyT xaM stinU

V

hgiHni

ttimhcS(egatlovtupnIleveLhgiH

)reggirt

3.3V

V

woLni

ttimcS(egatlovtupnIlevelwoL

)reggirt

8.0V

I

hgiHnI

hgihtupni-tnerrucegakaeltupnI010306Au

I

woLI

woltupni-tnerrucegakaeltupnI01-03-06-Au

Table 2. NEDSP1061 Electrical characeristics

2.5 Electrical characteristics.

Page 15

leveL 2N 1N 0N

1V0V0V0
2V0V0V3.3
3V0V3.3V0
4V0V3.3V3.3
5V3.3V0V0
6V3.3V0V3.3
7V3.3V3.3V0
8V3.3V3.3V3.3

Note:

The DSP has internal pull ups on its inputs, so any cell
in the table containing 3.3V may be left open circuit.
When processing signals with high levels of noise and
high levels of noise cancellation, the signal may sound
slightly strange. This is quite normal with this type of
signal.

4.4 Noise Cancellation On/Off

The module has the provision for remotely enabling and
disabling the noise reduction, while in operation. The
default setting for the module is noise cancellation on.
This may be switched by the use of the noise cancellation
on/off pin (PCB pin 8).

To inhibit noise cancellation, connect this pin to 0V.
T o enable noise cancellation leave the pin unconnected.

Table 5. Remote DSP level setting.

Output impedance: Nominally 10k Ohms
Input impedance: 7.5k Ohms typical

Page 11

3. Installation

Figure 4. Basic connection diagram

The NEDSP1061 module is inserted into the path of noisy
audio. Using the input and output level controls allows
the unit to appear transparent to the audio signal.

NEDSP1061 Power ampPre amp

Audio in Audio out

NEDSP1061 Power amp

Audio outMicrophone

Microphone

Pre amp

Audio in Audio out

Pre amp Power amp

NEDSP1061

Place NEDSP1061 module

in place of the coupling

capacitor

Figure 5. NEDSP1061 Audio path

Page 14

leveL 3PJ 2PJ 1PJ

1nOnOnO
2nOnOffO
3nOffOnO
4nOffOffO
5ffOnOnO
6ffOnOffO
7ffOffOnO
8ffOffOffO

4.3 Remote setting of DSP filter level.

Remote setting of the DSP level can be achieved through
the PCB connections. This allows the DSP filter level to
be changed during operation. If remote DSP setting is
used, remove the jumpers from the module.

These connections are connected directly to the DSP.
The logic levels of the DSP are 3.3V, do not apply a
voltage greater than this.

To set the DSP level remotely connect the pins N0, N1
and N2 (PCB pins 1,2, and 3) as shown on the following
page.

Table 4. Preset DSP levels using on board jumpers.

Page 12

The NEDSP1061 requires a signal of 50mV rms or
greater for optimum performance. Signals lower than this
may be used but the noise cancellation performance will
degrade, as the signal levels drops. If the unit is used
with low level microphones, the signal will need amplifying
before applying it to the NEDSP1061. The output level
can then be used to attenuate the signal back down to
the original signal level.

Figure 6. Signal levels.

Due to the adaptive nature of the noise cancellation a
small delay may be heard when the audio signal
changes. For optimum performance provide the module
with a constant signal, for example if the unit is installed
into a system employing a push to talk button - insert
the NEDSP1061 in to the audio path before the button.

Audio in Audio out

Input signal level Original signal level

NEDSP1061

635mV rms Max

Output level

Post processingPre processing

Gain = 1.7

>50mV rms

Page 13

4. Functions

4.1 Noise reduction levels.

8 levels of noise reduction are available. The amount of
noise and tone reduction is shown in the table below.

leveL noitcudeRenoT

esioNetihW

noitcudeR

1Bd4Bd9
2Bd5Bd11
3Bd6Bd31
4Bd8Bd51
5Bd61Bd71
6Bd12Bd02
7Bd52Bd42
8Bd56Bd53

4.2 Setting different filter levels.

The levels are set by applying a BCD code to three
jumpers on the module. See the table on the following
page for more information. The positions of the jumpers
are shown in section 2.1 module layout.

Table 3. Tone and noise reduction levels.