Microchip technology Parrot User manual

Parrot Hardware

Parrot (Voice Recorder) with ATtiny817 Hardware User's

Guide

Introduction

This user guide describes an audio demo board based on the ATtiny817, a high-performance tinyAVR® 8-

bit microcontroller.

The Parrot field engagement board can be used as a voice recorder to record, play back, browse, and

erase voice data. This application helps the user to quickly evaluate the ADC and DAC features of the

microcontroller.

The firmware and accompanying application note ( AVR42777) is available on Atmel START http://

start.atmel.com/.

Features

• Voice Record and Playback

• Electret Microphone

• Volume Control

• 8Mb SPI Data Flash

• Single-Wire Programming via UPDI

Table of Contents

Introduction......................................................................................................................1

Features.......................................................................................................................... 1

1. Block Diagram........................................................................................................... 3

2. Hardware Details....................................................................................................... 4

2.1. Microphone...................................................................................................................................4

2.2. Filter for ADC................................................................................................................................4

2.3. Microcontroller..............................................................................................................................5

2.3.1. ADC............................................................................................................................... 6

2.3.2. DAC............................................................................................................................... 6

2.4. Filter for DAC................................................................................................................................7

2.5. Power Amplifier............................................................................................................................ 8

2.6. User Interfaces............................................................................................................................. 9

2.6.1. Buttons...........................................................................................................................9

2.6.2. LEDs..............................................................................................................................9

2.7. External Data Flash....................................................................................................................10

2.8. UPDI Programming Interface..................................................................................................... 10

3. Firmware Programming........................................................................................... 12

3.1. Connection................................................................................................................................. 12

3.2. Firmware.................................................................................................................................... 12

3.3. Programming..............................................................................................................................12

4. Revision History.......................................................................................................14

5. Object of Declaration............................................................................................... 15

The Microchip Web Site................................................................................................ 16

Customer Change Notification Service..........................................................................16

Customer Support......................................................................................................... 16

Microchip Devices Code Protection Feature................................................................. 16

Legal Notice...................................................................................................................17

Trademarks................................................................................................................... 17

Quality Management System Certified by DNV.............................................................18

Worldwide Sales and Service........................................................................................19

Parrot Hardware

1. Block Diagram

ATtiny817

DACADC

SPI

Data Flash

AMP Filter Power

AMP

REC PLAY/STOP BACK FORWARD

GPIO x6

PWR REC

GPIO x2

3.3V

Volume

Control

ERASE

LDO

3.3V

User

The Parrot field engagement board demonstrates the capabilities of the ATtiny817 with audio processing,

using its ADC and DAC peripherals. It is possible to record, playback, erase, rewind, and fast forward by

using the buttons.

As shown in the figure above, once the “REC” (record) button is pressed, the electret microphone starts

to detect an analog sound signal. The sound signal will be processed in the front-end operation amplifier

and a low-pass filter will be applied to the signal. The signal will then be digitized by the ADC of the

ATtiny817 microcontroller. The converted sound data is stored in the external data Flash through the SPI

interface. When the button is pressed again, this recording process is stopped.

Once the “PLAY/STOP” button is pressed, the sound data stored in the data Flash is read and converted

to an analog signal through the DAC on the MCU. The analog signal is then sent through a low-pass filter

before it is sent to the amplifier with the set volume. This allows the user to listen to the previously

recorded sound. If the button is pressed again, the play process is stopped.

The board is supplied with +5V from the Micro-USB interface with ESD protection. The applied LDO can

source out 150mA @ 3.3V system power.

Figure 1-1. Parrot Board

Parrot Hardware

2. Hardware Details

2.1 Microphone

The device is a general low-cost electret microphone. See the table below for technical parameters.

It is highly recommended to keep the microphone at least 10cm away from the sound source to avoid

peak clipping or distortion of the signal.

Table 2-1. Microphone Parameters

Parameters Value

Manufacturer part number BL-MP6022P-2C-44DB

Standard operation voltage (DC) 2V

Active current <0.5mA

Sensitivity (1kHz, 0dB=1V/Pa) -44dB ±3dB

S/N ratio 58dB

Impedance < 2.2kΩ

Frequency (Hz) 20-16,000

Directivity Omnidirectional

2.2 Filter for ADC

As shown in the figure below, the power for the microphone is VCC_P3V3, which is filtered by a low-pass

filter to reduce noise from the power supply.

Typically, the original voice signal is quite weak, with measured amplitude around 10mV (less than

50mV). So the signal must be amplified and filtered accordingly. To make sure that the signal can be

amplified without being distorted, a voltage offset is required.

Figure 2-1. Microphone Circuit

1uF

C19

10k

R21

VCC_P3V3

SGND

TP5

BL-MP6022P-2C-44DB

GND

Microphone

MIC1

SGND

3.3nF

C20

SGND

C17

4.7uF

100k

R18

100nF

C15

R19

SGND

39k

R20

24k

R26

VCC_P3V3

ADC_VF_HALF

18k

R40

1uF

C18

As shown in the figure below, the original signal is processed in a 4-order Sallen-Key Butterworth low-

pass filter. The filter is designed to have a gain of 50 and a cut-off frequency of 4kHz. The amplified signal

is connected to the MCU ADC input 11 (pin PB0_AIN11).

Parrot Hardware

Figure 2-2. Amplifier and Filter Circuit

Mic. with Pre-Amplification and filter

TP6

U5B

MCP6002-I/SN

10nF

C39

5.6k

R39

1.5nF

C24

100nF

C22

GND

VCC_P3V3

15k

R42

PB0_AIN11 -

U5A

MCP6002-I/SN

SGND

VCC_P3V3

15k

R24

2.4k

R25

SGND

GND

1uF

C23

R44

10nF

C21

2.2nF

C16

11k

R23

6.8k

R22

SGNDSGND

2.4k

R43

1uF

C40

SGND GND

18k

R40

R41

The real filter response vs. frequency curve based on measured data is shown in the figure below.

Figure 2-3. Gain vs. Frequency Curve for the Low-pass Filter of the MIC

2.3 Microcontroller

The ATtiny817 is a tinyAVR 8-bit microcontroller with up to 8KB Flash, 512 bytes of SRAM, and 128 bytes

of EEPROM in a 14-, 20-, and 24-pin package.

The microcontroller uses the latest technologies from Microchip Technology Inc. with a flexible and low-

power architecture including Event System and SleepWalking, accurate analog features, and advanced

peripherals.

Parrot Hardware

2.3.1 ADC

The Analog-to-Digital Convert (ADC) peripheral features a 10-bit successive approximation ADC with

capability of a sampling rate of up to 150ksps. The ADC is connected to a 12-channel Analog Multiplexer,

which allows twelve single-ended voltage inputs. The single-ended voltage inputs refer to 0V (GND).

For more detail, refer to the latest data sheet of ATtiny817 available at http://www.microchip.com/

wwwproducts/en/attiny817.

Figure 2-4. ATtiny817 ADC Block Diagram

ADC

AIN0

AIN11

DAC

VREF

RES

CTRLA

MUXPOS

EVCTRL

CTRLC

WINLT

WINHT

Internal ref

VDD

Reference sel.

prescaler

COMMAND

accumulate

Start

Conversion

Threshold

(IRQ)

Result Ready

(IRQ)

Enable,

Resolution

...

CTRLB

Number of

Accumulated

Samples

AIN1

VREF

TEMP

2.3.2 DAC

The Digital-to-Analog Converter (DAC) converts a digital value to a voltage. ATtiny817 features an 8-bit

Resistor String type DAC, capable of converting 350,000 samples per second (350ksps), with the internal

Voltage Reference (VREF) as upper limit for conversion. The DAC has one continuous time output with

high drive capabilities, which is able to drive a 5kΩ or 50pF load. The DAC has one analog output pin

(DACOUT), namely the PA06, that must be configured before it can be used.

Parrot Hardware

Figure 2-5. ATtiny817 DAC Block Diagram

DAC

DATA Output

Driver

CTRLA

ENABLE

OUTEN

VREF

peripherals

other

OUT

2.4 Filter for DAC

This filter is an 8-order Butterworth low-pass filter with 1V/V gain. The cut-off frequency is designed to be

4kHz with 0.5dB allowable pass band ripple.

Figure 2-6. 8-order Low-pass Chebyshev Filter

TP4

U3A

MCP6002-I/SN

U3B

MCP6002-I/SN

U2A

MCP6002-I/SN

U2B

MCP6002-I/SN

PA6_DACOUT

1uF

150k

100k

150k

470pF

SGND

220pF

GND

VCC_P3V3

330k

180k

330k

270pF

SGND

100pF

330k

300k

R10

330k

330pF

C10

SGND

47p

330k

R11

270k

R12

330k

1nF

C11

SGND

18pF

GND

VCC_P3V3

1uF

OP AMP Filter

100nF

C12

GND

VCC_P3V3

100nF

C13

GND

VCC_P3V3

SGND

39k

R16

24k

R17

VCC_P3V3

100nF

C14

DAC_VF_HALF

As shown in the figure below, the curve is based on measured data of the filter on the board.

Parrot Hardware

Figure 2-7. Gain vs. Frequency Curve for the 8-order Low-pass Filter

2.5 Power Amplifier

Figure 2-8. Power Amplifier for the Speaker

MCP6002-I/SN

1uF

TP3

GND

10R

R14

47nF

110k

R13

VCC_VBUS_P5V0

TP1

TP2

BTL AMP for Speaker

SGND

8 ohm, 2W

Speaker 2831

SP1

LM386M-1

GND

VCC_VBUS_P5V0

WH0141-1(14*1) B10K

1 3

VR1

POT_METER_3P S2B-PH-K-S

HEADER-2

100k

R15

SGND

C38

4.7uF

VCC_VBUS_P5V0

GND

SGND

As shown in the figure above, the LM386M-1 amplifier device is powered by USB +5V. The gain from the

power amplifier circuit is fixed to 20 V/V. The input of this circuit is the analog output of the 8-order low

power filter for the DAC.

In front of the power amplifier, one variable resistor (VR1) and a couple of relative resistors construct a

simple circuit for the users to adjust the loudspeaker volume.

Parrot Hardware

2.6 User Interfaces

2.6.1 Buttons

There are six functional buttons on the board:

• “REC” button, to start or stop the microphone recording

• “PLAY/STOP” button, to playback the recorded sound

• “BACK” button, to jump to previous sound data

• “FORWARD” button, to jump to forward sound data

• “ERASE” button, to erase sound data

• “USER” button, reserved for users

Figure 2-9. Buttons

4 2

SKRAAKE010

SW1

GND

100k

R28

User Button

PC5_USER_BTN

100nF

C30

VCC_P3V3

TP8

1 3

SKRAAKE010

SW2

100nF

C33

GND

REC.

R34

1 3

SKRAAKE010

SW3

100nF

C34

GND

PLAY/STOP

R35

1 3

SKRAAKE010

SW4

100nF

C35

GND

BACK

R36

1 3

SKRAAKE010

SW5

100nF

C36

GND

FORWARD

R37

TP17 TP18 TP19 TP20

PB5

PB6

PB7

PA7

1 3

SKRAAKE010

SW6

100nF

C37

GND

ERASE

R38

TP21

PB4

This button is

reserved for user.

Table 2-2. Pin Map for the Buttons

Button Name I/O Pin

REC PB4

PLAY/STOP PB5

BACK PB6

FORWARD PB7

ERASE PA7

USER PC5

2.6.2 LEDs

There are two LEDs on the board, as shown in the figure below. The firmware determines the use of the

LEDs.

Figure 2-10. Status LEDs

Parrot Hardware

Table 2-3. Pin Map for the LEDs

Recommended LEDs name ATtiny817 I/O pin Color

Power LED PB3 Green

Record LED PB2 Red

2.7 External Data Flash

This data Flash from Microchip is an 8Mb SPI serial Flash. It supports single voltage read and write

operations under 2.7-3.6V power supply.

Figure 2-11. External Data Flash

Table 2-4. Pinout for the SPI Interface

SPI Signal Name MCU SPI Pin Data Flash Pin

SCK PA3 pin #6

SS PA4 pin #1

MISO PA2 pin #2

MOSI PA1 pin #5

2.8 UPDI Programming Interface

The ATtiny817 supports UPDI (Unified Program and Debug Interface), which is a Microchip proprietary

interface for external programming and on-chip debugging of a device.

Atmel-ICE supports the UPDI interface. The 2x3 connector for the interface is a 2.54mm pitch through-

hole header.

Parrot Hardware

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