Copyright © 2016 ARM Limited 4

A Sneak Peak of What’s Ahead

A tunable single biquad tunablenotch filter, using a GUI slidercontrol talking through the FM4virtual serial port

Use GPIO for code timing

Inputs Outputs

Power,Debug,UART

3.5mm to jumper adaptors

Low Cost/High Performance Audio Digital

Signal ProcessingMark Wickert, PhD. and Professor (mwickert@uccs.edu)

College of Engineering and Applied Science, University of Colorado Colorado Springs, CO 80933-7150

Introduction• Using a lost-cost development kit explore audio signal processing using an

ARM(R) Cortex(R)-M4 microprocessor

• In this project we use the Cypress FM4 Pioneer Kit ($50) to develop audio signal processing applications, such as filtering, audio special effects, and spectrum analysis, to name a few

• A configurable PC GUI app allows for real-time control of DSP apps run-ning on the FM4

• Hands-on interactive demos allow you to hear and see signals being pro-cessed from audio sources such as a microphone(s) and music players

• Algorithms from simple to very complex can be implemented on the FM4 with its 200 MHz clock and floating point math capabilities

• We use Python’s scipy stack to design filters and analyze captured results from the Digilent Analog Discovery 2 portable instrumentation system

Buy On-Line From Cypress Semiconductor

• Consider the text: Donald S, Reay, Digital Signal Processing Using the ARM(R) Cortex(R)-M4, Wiley 2016, which has Web Site suport for the FM4

• Visit my Web Site: www.eas.uccs.edu/~wickert/ece4680/ and look for Lab 3 and the associated ZIP package plus other documents

◊ The code base for audio loop through and the GUI slider app is included

Copyright © 2016 ARM Limited 8

The Cypress® FM4 S6E2CC Pioneer Kit*

http://www.cypress.com/documentation/development-kitsboards/fm4-176l-s6e2cc-eth-arm-cortex-m4-mcu-starter-kit-ethernet-and

*

FM4 Board and Subsystems• The system out-of-the box is enhanced through the use of the virtual se-

rial port (com port), the GUI slider control, and the Analog Discovery for test and measurement

◊ CPU clock is 200 MHz, with single cycle floating point multiply & add

Copyright © 2016 ARM Limited 11

FM4 + LiB Docs & Software + Enhancements

Top level view of the board andstandard interfaces and tools used

Lab-in-a-Box (LiB):LiB_DSP_FM4_S6E2CCA_EN\DSP_LiB_Index.html

LiB codec library analog I/O systemblock diagramΣ∆

ADC

Cypress FM4 S6E2CC

L

R

Cortex-M4L

R

Σ∆DAC

I2S I2S

f ≤ 96skHz

RS232

IDEKeil MDK

GUI Para-meter Sliders

PC Host

...P0 P1 P5

R/W to M4 inreal-time

Tx RxUSB serial460800 bps

TerminalProgram

GPIO

USB for Timing Debug

Digilent AnalogTM

Discovery

Interface Wires

Capture &analyze in

Python

Code dev., debug, & prog. flash

Debug M4Code

In Out

ADC

ADC

I2S 2:1

Single Sample

ProcessingI2S 1:2

DAC

DAC

L

R R

L

...LRLRLR... ...LRLRLR...

ADC

ADC

I2S 2:1

I2S 1:2

DAC

DAC

L

RDMA

pingOUT

pongOUT

pingIN

pongIN

BUFSIZE BUFSIZE

L

R

(b) Frame-Based Processing

(a) Sample-Based ProcessingProcess one sample per IRQ

Process BUFSIZE (L + R) samples per DMA cycle

Systems Level M4 or M7 Hardware

ECE 5655/4655 Real-Time DSP 1–15

Systems Level M4 or M7 Hardware

• Many hardware/dev kit options available:

– Last year the STM32F407 (M4) (~168 MHz)

– NXP LPC4088 + Baseboard (M4) (~120 MHz)

– TI Tiva TM4C123G (M4) + Audio Booster Pak (~80MHz)

– Cypress FM4 (M4) (200 MHz)

– STM32F746 (M7) (~212 MHz)

– Others? Yes!

ARM CortexM4 or M7

Used for DSPADC DAC

Analog Input(two channel)

Analog Output(two channel)

Cypress FM4Pioneer Kit

Interfaces added in purple

Out of the box

Chapter 5 • Analog Input and Output

5–8 ECE 5655/4655 Real-Time DSP

Wolfson WM8731 Codec on Cypress FM4

• We now provide some details about the internals of theAudio codec found on the Cypress FM4 board, in particularthe ADC and DAC characteristics

• The FM4 specific circuit interfaces give some insight intoadditional filtering in the analog domain

Line InMic In

HeadphoneOut

C390.1uF

C4010uF/6.3V

C35 1uF/10V

C36

220pF

R64

5.6k

C34 1uF/10V

C37

220pF

R65

5.6k

R60 330RC33

1uF/10V

C38

220pF

R66

47k

R57 680R

R5547k

R5647k

C290.1uF

C3010uF/6.3V

I2SAGND

AVCCCodec

C220.1uF

C2310uF/6.3V

AVCCCodec

I2SAGND

C260.1uF

C2810uF/6.3V

C250.1uF

C2710uF/6.3V

VCCCodec

VCCCodec

I2SAGND I2SAGND

I2SAGND I2SAGND I2SAGND

R624.7k

R634.7k

3V3

Pin25

Pin42

Pin43

Pin24

bit clockI2SCK_0

I2SDO_0data out

I2SDI_0data input

I2SAGND

AVCCCodecVCCCodecL1

10uH/100mA

Pin36

Pin37

SOT2_1

SCK2_1

C4122pF

C4222pF

C31 220uF/10V

C32 220uF/10V

R54 33R

R67 100RPin41 I2SMCLK_0

I2SAGND

LIN_R

LIN_L

I2SAGND

Headphone Jack

Line-in Jack

frame clockI2SWS_0 R59

0RR58 33R

Default clock : derived from WM8731L

Address : 0x1ACodec

HP_L

HP_R

R92

5.6kR91

5.6k

R93 33R

R94 33R

132

4

Y312.288000MHz,50ppm

XTI/M

CLK

25

XTO

26

DCVDD27

DGND28

DBVDD1

DACDAT4

DACLRC5

ADCDAT6

BLCK3

MODE21

CSB22

SDIN23

SCLK24

MICBIAS 17

MICIN 18

LHPOUT 9

RHPOUT 10

RLINEIN 19

LLINEIN 20

LOUT 12

ROUT 13

AVDD 14

AGND 15

HPVDD 8

HPGND 11

VMID 16

CLKOUT2

ADCLRC7

U3

WM8731SEDS/VStereo CODEC, 28SSOP

13

2 CN6

PJ-31060-5

13

2

CN11

PJ-31060-5

13

2 CN5

PJ-31060-5

I2SAGND

MICIN

Microphone Jack

R109 NC[100R]

HighpassDC Block

DC Block

High frequency reject

Line In

HeadphoneOut

Mic In

on all inputs

Analog Interface Details and Codec Software• Line and Mic inputs are provided and a headphone output jack that dou-

bles as line out is also provided

• The Codec interface code found in the Reay text provides both sample-by-sam-ple and frame-based processing using di-rect memory access (DMA)

Programming the Board• ANSI C is used for programming with the MISRA + ARM data types (https://

en.wikipedia.org/wiki/MISRA_C)

• Shown below is a basic loop through program under GUI slider control

Copyright © 2016 ARM Limited 31

LAB_3_UART: DDS I/Q Sinusoids

ADC

cosf() sinf()DDS

LPF𝑓𝑓𝑓𝑓 𝑓 𝑓𝑓𝑓𝑓

LPF𝑓𝑓𝑓𝑓 𝑓 𝑓𝑓𝑓𝑓

𝑥𝑥𝑥𝑥[𝑛𝑛𝑛𝑛]𝑥𝑥𝑥𝑥𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹(𝑡𝑡𝑡𝑡)

𝑓𝑓𝑓𝑓𝑠𝑠𝑠𝑠 = 48 kHz• Choose carrier

frequencyaround 10 – 15kHz

• Maybe use asecond FM4 asa custom signalsource with aPN code drivinga DDS toproduce binaryFSK

Complex Baseband

Discriminator

𝑧𝑧𝑧𝑧𝐼𝐼𝐼𝐼[𝑛𝑛𝑛𝑛] 𝑧𝑧𝑧𝑧𝑄𝑄𝑄𝑄 𝑛𝑛𝑛𝑛 𝑛 𝑧𝑧𝑧𝑧𝑄𝑄𝑄𝑄 𝑛𝑛𝑛𝑛 𝑛 1 𝑛 𝑧𝑧𝑧𝑧𝑄𝑄𝑄𝑄[𝑛𝑛𝑛𝑛] 𝑧𝑧𝑧𝑧𝐼𝐼𝐼𝐼 𝑛𝑛𝑛𝑛 𝑛 𝑧𝑧𝑧𝑧𝐼𝐼𝐼𝐼 𝑛𝑛𝑛𝑛 𝑛 1

𝑧𝑧𝑧𝑧𝐼𝐼𝐼𝐼2 𝑛𝑛𝑛𝑛 + 𝑧𝑧𝑧𝑧𝑄𝑄𝑄𝑄2[𝑛𝑛𝑛𝑛]

𝑥𝑥𝑥𝑥𝐼𝐼𝐼𝐼[𝑛𝑛𝑛𝑛]

𝑥𝑥𝑥𝑥𝑄𝑄𝑄𝑄[𝑛𝑛𝑛𝑛]

𝑧𝑧𝑧𝑧𝐼𝐼𝐼𝐼[𝑛𝑛𝑛𝑛]

𝑧𝑧𝑧𝑧𝑄𝑄𝑄𝑄[𝑛𝑛𝑛𝑛]𝑧𝑧𝑧𝑧𝑑𝑑𝑑𝑑[𝑛𝑛𝑛𝑛]

Set CarrierFrequency to

Translateto Baseband

DAC 𝑥𝑥𝑥𝑥𝑚𝑚𝑚𝑚(𝑡𝑡𝑡𝑡)

Eliminate denominatoris OK to simplifyMath and scaling

Results in a 25 tap filter, but you need two of them

𝑓𝑓𝑓𝑓𝑠𝑠𝑠𝑠 = 48 kHz

FM Receiver

Other Examples• Frequency modulation receiver (discriminator)

• Spectrum analyzer

• Others to see in the DEMOs

Copyright © 2016 ARM Limited 38

Real-Time Spectrum GUI Slider with PlotCopyright © 2016 ARM Limited 34

LAB_6_UART_FFT: Real-Time Spectrum

FM4 ADCLeft

FM4 ADCRight

InternalNoise

∑

X

𝑃𝑃𝑃𝑃𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑠𝑠𝑠𝑠[0]

X

𝑃𝑃𝑃𝑃𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑠𝑠𝑠𝑠[1]1024 PointFFT

X

𝑃𝑃𝑃𝑃𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑠𝑠𝑠𝑠[2]

X

𝑤𝑤𝑤𝑤hann[𝑛𝑛𝑛𝑛]

2

512

Left and rightanalog inputs

Spectrum Analyzer

GUI Display on PC

Spectrum Averaging

Collect subframes using a 128 point DMA buffer

𝑓𝑓𝑓𝑓𝑠𝑠𝑠𝑠 = 48 kHz

SpectrumAnalyzer

GUI Slider App with plot added