Renesas Electronics America Inc.
© 2012 Renesas Electronics America Inc. All rights reserved.
Class ID:
Audio Solutions on the RX MCU Family
Mitch Ferguson, Applications Engineering Manager
5L071
© 2012 Renesas Electronics America Inc. All rights reserved. 2 2
Mitch Ferguson
Applications Engineer Manager
Provides support of design teams using ADCs in MCU system.
Over 15 years of system-level design experience
Over 7 years of experience as an application engineer.
As a hardware engineer and engineering manager, he has been involved in design in power distribution controls, automotive and fire alarm systems with focus on analog design and EMI/EMS issues.
Bachelor of science in electrical engineering from Cleveland State University
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Renesas Technology & Solution Portfolio
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Microcontroller and Microprocessor Line-up
Wide Format LCDs Industrial & Automotive, 130nm
350µA/MHz, 1µA standby
44 DMIPS, True Low Power
Embedded Security, ASSP
165 DMIPS, FPU, DSC
1200 DMIPS, Performance 1200 DMIPS, Superscalar
500 DMIPS, Low Power
165 DMIPS, FPU, DSC
25 DMIPS, Low Power
10 DMIPS, Capacitive Touch
Industrial & Automotive, 150nm
190µA/MHz, 0.3µA standby
Industrial, 90nm
242µA/MHz, 0.2µA standby
Automotive & Industrial, 90nm
600µA/MHz, 1.5µA standby
Automotive & Industrial, 65nm
600µA/MHz, 1.5µA standby Automotive, 40nm
500µA/MHz, 35µA deep standby
Industrial, 40nm
242µA/MHz, 0.2µA standby
Industrial, 90nm
1mA/MHz, 100µA standby
Industrial & Automotive, 130nm
144µA/MHz, 0.2µA standby
2010 2013
32-b
it
8/1
6-b
it
© 2012 Renesas Electronics America Inc. All rights reserved. 5
Microcontroller and Microprocessor Line-up
Wide Format LCDs Industrial & Automotive, 130nm
350µA/MHz, 1µA standby
44 DMIPS, True Low Power
Embedded Security, ASSP
165 DMIPS, FPU, DSC
1200 DMIPS, Performance 1200 DMIPS, Superscalar
500 DMIPS, Low Power
165 DMIPS, FPU, DSC
25 DMIPS, Low Power
10 DMIPS, Capacitive Touch
Industrial & Automotive, 150nm
190µA/MHz, 0.3µA standby
Industrial, 90nm
242µA/MHz, 0.2µA standby
Automotive & Industrial, 90nm
600µA/MHz, 1.5µA standby
Automotive & Industrial, 65nm
600µA/MHz, 1.5µA standby Automotive, 40nm
500µA/MHz, 35µA deep standby
Industrial, 40nm
242µA/MHz, 0.2µA standby
Industrial, 90nm
1mA/MHz, 100µA standby
Industrial & Automotive, 130nm
144µA/MHz, 0.2µA standby
2010 2013
32-b
it
8/1
6-b
it
© 2012 Renesas Electronics America Inc. All rights reserved. 6
Microcontroller and Microprocessor Line-up
Wide Format LCDs Industrial & Automotive, 130nm
350µA/MHz, 1µA standby
44 DMIPS, True Low Power
Embedded Security, ASSP
165 DMIPS, FPU, DSC
1200 DMIPS, Performance 1200 DMIPS, Superscalar
500 DMIPS, Low Power
165 DMIPS, FPU, DSC
25 DMIPS, Low Power
10 DMIPS, Capacitive Touch
Industrial & Automotive, 150nm
190µA/MHz, 0.3µA standby
Industrial, 90nm
242µA/MHz, 0.2µA standby
Automotive & Industrial, 90nm
600µA/MHz, 1.5µA standby
Automotive & Industrial, 65nm
600µA/MHz, 1.5µA standby Automotive, 40nm
500µA/MHz, 35µA deep standby
Industrial, 40nm
242µA/MHz, 0.2µA standby
Industrial, 90nm
1mA/MHz, 100µA standby
Industrial & Automotive, 130nm
144µA/MHz, 0.2µA standby
2010 2013
32-b
it
8/1
6-b
it
32-Bit High Performance DSP, FPU with High Integration
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‘Enabling The Smart Society’
Challenge: “Improving the interface to the new smart machines is one of the important concepts of the Smart Society. Audio is an effective way of improving information delivery”
Solution:
“This class will show you how simple it can be to add various levels of audio to your next project”
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Agenda
Discuss audio formats and requirements
Embedded applications not high quality music players
Hardware Requirements
DAC
PWM
RX Audio Demo Components
Basic decoding scheme
Peripheral Blocks
Lab
Summary
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Audio Experience
BMW pursuing better acoustics to improve efficiency
Audio used to compensate for low RPM rumble
- At Mercedes-Benz...engineers record the sounds of those servo motors used to raise the windows and adjust the seats, then compare them with sounds made by a BMW and other competitor
if it sounds well made, it probably is
Do Your Products Sound Priceless?
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Audio Considerations
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Key Considerations
What type of audio is needed
Simple tones
Speech
Music
What are characteristics and requirements
File size
– Internal Flash
– External file storage
– File system
MCU and Bus Bandwidth
Transducer (speaker)
Amplifier/filter requirements
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Sample Rates and Quality
8kHz, 8 bits
Telephone quality
11kHz
passable voice
22kHz, 8 bits,
good for a mix of mono speech and music.
44.1kHz , 16 bits
Good for audio and quality speech
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Telephone or Voice quality
Bandwidth: 180 Hz to 3.2 kHz
Low end avoids 60 Hz region.
Noise pickup
Size of transformers
High end bandwidth issue
8 kHz sampling rate
sufficient for speech intelligibility
Signal to Noise: Approximately 45 dB
Human voice extends from 80 Hz to 14 kHz
Lab will investigate voice quality
Spectrum of Audio Clip
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Bandwidth, Storage and Dynamic Range
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Dynamic Range – How many bits?
48 dB = 8 bit
60 dB = 10 bit
96 dB = 16 bit
144 dB = 24 bit
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Improving Dynamic Range Use signal compression techniques
u-Law or A-law
– 8 bit data, 8K sampling rate = 8kB/sec
– Compression ratio 2:1
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Signal Compression - ADPCM
PCM stores digitized audio - WAVE is a PCM file
DPCM (Differentia) stores the difference from predicted last sample
ADPCM – Adaptive – adapts step size for better compression (4:1}
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Audio Data Compression
Format (compression type) Bitrate (Kbps) Filesize (KB/min)
Uncompressed WAV 1411 105,000
MP3 128 960
MP3 (VBR) 112 840RA 96 720
WMA 92 690
OGG 112 840
MPC 88 660
AAC 80 600
AC3 967 720
Comparison Audio Files
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Hardware requirements
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DAC or PWM Output
Which is better?
DAC is simple
DAC resolution must be considered
DAC settling time may limit actual audio range
PWM very flexible, available on most MCUs
PWM resolution may be limited depending on carrier
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Filter Considerations
DAC output should have filter
Basically same requirement as anti-aliasing filter on ADC
Should filter all frequencies above sampling rate/2
May cause amplitude distortion
Buffer and filter can be combined
Output resistance of the DAC should be considered in the filter design
Simple RC acceptable in many applications
Some systems like audio the speaker or listener filters many of the unwanted higher frequencies
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PWM vs DAC Resolution
At 10 kHz DAC settling time (3 uS) should not be a problem so all 1024 states of 10 bit DAC available
Using 16 bit MTU timer
48 Mhz / 44.1 kHz = 1088
Can utilize more that 10 bits (1024)
Increased resolution just adds audio dynamic range
If a lower resolution audio is used interrupts can be “skipped” while still using PWM carrier
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DAC Output Resistance
Important specification of DAC
Relatively high for many MCU DACs
May require buffering in many cases
Some MCUs have internal buffer
If no internal buffer
Rload >> Ro to prevent loading
Rload>2*Resolution* Ro for <1/2 bit error
Ro on RX63N is 3.6K
DAC
Ro Rload
Vload
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DAC Filter
Frequency / Hertz
500m 1 2 5 10 20 50 100 200 500 1k 2k 5k 10k 20k 50k 100k
Gain
/
10m
20m
50m
100m
200m
500m
1
2.5 kHz First Order Filter
Typically first order filter not enough
Often use amplifier and filter
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Filter Considerations
Time/mSecs 1mSecs/div
-0 1 2 3 4 5
V
-1.2
-1
-0.8
-0.6
-0.4
-0.2
-0
0.2
0.4
0.6
0.8
1
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RX Audio Demo
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Renesas RX63N RDK J-Link
debugger
Speaker
Stereo headphone
jack
LED
Ring
SD-Card
Graphics
LCD
User push
buttons
POT
VR1
MIC and
amplifier
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RX Audio Demo
SD-Card stack & low-level drivers
FAT file system browser
Supports
MP3
WAV
ADPCM
Stereo PWM output
Software volume control
YRDK RX63N
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RX Audio Demo - supported formats
MP3
MPEG-1/Audio(ISO/IEC11172-3)LayerIII
MPEG-2/Audio(ISO/IEC 13818-3)LayerIII
MPEG-2.5 (For Low Sampling Frequencies)
ADPCM
WAV (uncompressed PCM)
16-bit stereo or mono ( 1 or 2 channels)
Sample rates (kHz)
44.1, 33.075, 22.05, 11.025
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RX Audio Demo Decode path block diagram
SD-Card
RSPI MMC FAT MP3 Render
Raw binary Blocks File I/O MP3
decode Timers
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RX Audio Demo
Rendering block diagram
Render
Ping
Pong
DTC TPU
L
R
Sample Rate
Ready for next PCM data sample
Reload
Load next PCM sample
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Timer Operation
Timer count value
Elapsed time
TPU1.TGRB
TPU0.TGRA
TPU0.TGRB
TPU1.TGRB clears all channels at the audio sample rate
Channel A PWM
Channel B PWM
Sets Playback Rate
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RX Audio Demo
MCU peripherals used
Two synchronizable "TPU" timer channels for PWM
audio rendering.
Data Transfer Controller (DTC) for streaming PWM
timer data to the TPU timers.
RSPI channel for SDCard communication
12-bit ADC to measure the potentiometer setting
for audio playback volume
1 Compare Match Timer (CMT) channel for timed
delays in SDCard driver code
Real-time clock (RTC)--used for file time stamp
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Lab Time !
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Summary
Audio formats and requirements
How good is “voice quality”
Hardware
DAC
PWM
Audio
Various quality levels depending on need
Trade-off
– File storage size
– Decode bandwidth
– Quality
© 2012 Renesas Electronics America Inc. All rights reserved. 36
Questions?
© 2012 Renesas Electronics America Inc. All rights reserved. 37
‘Enabling The Smart Society’
Challenge: “Improving the interface to the new smart machines is one of the important concepts of the Smart Society. Audio is one of the most effective ways of improving information delivery”
Solution:
“This class will show you how simple it can be to add various levels of audio to your next project”
© 2012 Renesas Electronics America Inc. All rights reserved. 38
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or
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Renesas Electronics America Inc.
© 2012 Renesas Electronics America Inc. All rights reserved.