Lab D Lecture Slides - UMass Amherst ECE 353

ECE 353 Lab D
General MIDI Explorer
Instructor and UGA Presentation,
and Demo
Professor Sandip Kundu
Fall 2014
Lab D
General MIDI Explorer
with Record/Playback
Getting Started
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Where Are We?
Lab A
Cache Simulator in C
Lab B
MIDI Receiver
Lab C
Pipelined Machine
• C programming, data structures
• Cache architecture and analysis
• Hardware design
• Proper Verilog Coding
• Functional Simulation, GoLogic, MIDI-Ox
• C programming, data structures
• Pipeline architecture and analysis
Lab D General MIDI Explorer with Record/Playback
• Microcontroller programming
• C and Assembly (optional)
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Perspective
• As an engineer you often have multiple choices for
implementation
• What you do will depend on performance and cost
requirements
• Use a CPLD, FPGA, ASIC/microprocessor, or
microcontroller
• Write it in Verilog (CPLD, FPGA, ASIC) => Lab B
• Write it in C or ASM => Lab D
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When to use: PLDs, FPGAs, ASICs, Structured ASICs
• Programmable logic devices (PLDs) provide low/medium density
logic.
• Field-programmable gate arrays (FPGAs) provide more logic and
multi-level logic. Advanced peripheral support.
• Application-specific integrated circuits (ASICs) are manufactured for a
single purpose. Typically built with standard cells implementing gates.
Higher performance vs. FPGAs.
• Structured ASICs are in between FPGAs and ASIC in density &
performance. Typically wire together cells that are pre-built and exist
in island configurations.
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Differences between microcontrollers, microprocessors
and FPGA systems for running software

FPGA systems often contain CPUs
in softcore (synthesized) or
hardcore (part of die) format but can
also contain logic blocks for other
hardware, e.g., state machines, etc
•

Tx
Rx
Discrete
PHY
45-65 nm FPGAs (Virtex 5-7) can
achieve high performance.
Microcontrollers are more limited in
functionality and often do not
include support for virtual memory
and caches
•

Soft core
Up to 50MHz
Microprocessors are higher
performance capable and have
typically virtual memory support
•
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From 50MHz to GHz
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Tx
Rx
Hard core with builtin Transceivers
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Lab D Objectives
• Exposure to microcontroller programming vs.
design of hardware
• Compiled Language (C)
• Data Structure in Memory
• Talking to UART, Timer
• Assembly Language (ASM) - optional
• Talking to A/D converter, Timer, UART
• Continuation of MIDI theme
• Serial communication
• Notes and instruments
• Complete system with MIDI – FUN! with input, output,
storage
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Lab D Requirements
• Part 1: C Program
• Send & Receive MIDI Messages
• Play and Recording Modes
• Store and Replay MIDI Messages
• Part 2: ASM Program (optional)
• Vary speed of messages via hex switch
• Instrument / Note / Velocity via photo cells
• Change channels between Percussion & Instrument
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AVR Components Used
• In Part 1 (C Program)
• Data EEPROM (Storage)
• USART (Communication)
• Timer1 (Counter)
• In Part 2 (ASM Program)
•
•
•
•
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Timer1 (Counter)
USART (Communication)
ADC (Analog to Digital Converter)
Will manipulate these components using AVR assembly.
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ATmega32 AVR
•
•
•
•
•
•
•
•
•
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16MHz CMOS 8-bit microcontroller
with AVR RISC instruction set
32 general purpose registers
32KB of Flash
2Kb internal SRAM
1KB E2PROM – 100,000 erase
cycles
8 and 16 bit counters
USART
8-bit ADC
JTAG
….
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Board Demonstration
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Wired Board
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Part 1 – C Program
•
Develop, program AVR through JTAG, for:
•
Getting MIDI messages through the Midi OX
from the PC serially
•
Similar to Lab B but using AVR Studio
and AVR gcc compiler – to receive
Input
Play Switch
Input
Record Switch
ATMega32
EEPROM
DATA
USART
To PC
Transmit
From PC
Receive
C Program Block Diagram
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Part 1 – C Program contd.
•
Once received in AVR, store in E2PROM if switch
set to Record
•
Compress/decompress before/after
storing - you can use any algorithm you
find suitable
•
Record timing also so that you can replay
exactly the same way
•
If switch set to Playback, play back
Input
Play Switch
Input
Record Switch
•
Incoming signal optically isolated from PC
ATMega32
EEPROM
DATA
USART
To PC
Transmit
From PC
Receive
C Program Block Diagram
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Compression
• Why compress?
• Store more data in same persistent memory
• Persistent data limited in # of erase cycles
• Save on bandwidth when communicating in some apps
• Lossless compression (LZ, Huffman, RLE):
• Decompress and get the same data, bit - for - bit
• Lossy compression (JPEG,…):
• Decompress and get something *similar*.
• Any amount of compression is possible.
• Tradeoff between quality and compression.
• Domain specific
• You may understand the pattern, e.g., in the case of MIDI
messages there is a repetition that could be exploited.
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Example: Run Length Encoding (RLE)
•
•
Very simple lossless encoding of repeating patterns
Example: Imagine a stream of bits with many 0s and 1s
•
•
Source: 000000000111111110001111111
RLE Version: 9Zeros8Ones3Zeros7Ones
• Can be transformed into a sequence of 1s and 0s but we often limit the encoding of
the maximum sequence value to avoid too much overhead for very random
sequences.
• Say we limit to maximum 16 repetition of 1s or 0s: represent with 4 bits
• 1001(0)1000(1)0011(0)0111(1) for the above sequence
• Best we get is minimum 5 bits needed for a sequence of length 16, or a
compression ratio of 16/5
• 111111111111111 => 1111(1)
• Worst we get an overhead of how much?
• To avoid, change algorithm to have a first bit encode WHEN RLE is used
•
RLE can be applied at various granularities
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Example of lossy compression - JPEG compression
Very high quality:
compression = 2.33
Photoshop Image
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Very low quality:
compression = 115
Produced by MATLAB
with Quality = 0
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For Part 1 you need to figure out how to
• Initialize the USART
• Set baud rate for midi
• Enable the receiver and transmitter
• Initialize to 8 data bits, 1 stop, and 1 stop bit
• Create functions for receive, transmit, and flush USART
• Create functions to read and write E2PROM
• Work with timers and interrupts
• Use 16-bit counter and generate interrupts for overflows; need to setup
ISR (interrupt service routine)
• Main function
• Use LEDs to debug, try something simple first
• All information is in AVR datasheet; sample codes
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Part 2 – AVR ASM Program
•
Develop, program AVR through JTAG
•
Use the three optical sensors that are
connected to three ADC inputs on AVR to
generate instrument, note, and velocity MIDI
bytes
•
Use the internal AVR counter to synchronize
when sending back MIDI messages to PC
•
•
Sets 1 bit into register, your code will
be polling
•
Speed-dial hex switch on board
Input
ADC
Analog Signal (Photocells)
Input
ATMega32
ADC
Converter
Timer1
To PC
Transmit
USART
ASM Program Block Diagram
Use GPIO connected switch
•
•
Hex Switch
Instrument Switch
To program channel select
(percussion, instrument)
Note that you will see 2 byte message for
program channel selection and the typical 3
bytes for the message that contains note and
velocity
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Build Process
 Board Assembly
 C & Assembly Programming
• AVR Studio (IDE)
• Olimex JTAG Programmer
 Testing
• MIDI-OX
• GoLogic Logic Analyzer
• Oscilloscope
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Board Assembly

Reuse parts of Lab B
• MIDI input (Optoisolator)

Plan for both programs if
you decide to do both C
and ASM versions
• Layout should be
compatible with both

Use resistors as indicated
in schematic
• Otherwise photo-senors
may not work correctly
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AVR Studio




Atmel IDE
Tool chains for building C and assembly code
Programmer
Debug
 Easier to use than Quartus!
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AVR Studio Demonstration
• Open up a new instance of AVR Studio 4
• When the welcome screen pops up, click New Project
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AVR Studio Demonstration
• Select AVR GCC for the project type
• Type in project title and choose project directory if necessary
• Click next and choose the debugging platform used to program
the MCU as well as the MCU that you are using
• Now go to Project --> Configurations and choose the MCUs
clock frequency.
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AVR Studio Demonstration
• Start Coding!
• When finished, 1.build your project and then 2.connect to the
MCU.
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AVR Studio Demonstration
• Once you connect to your MCU, erase the device and then load
up the .hex file created in your project directory on to the Flash
Memory.
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AVR Studio Demonstration
• Click on program to load your .hex file on to the board.
• Now open up MIDI OX and set it up like you did in Lab B.
• Start sending notes to your board!
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Testing
 Familiar tools
• MIDI-OX
• GoLogic Logic Analyzer
• Analyzer individual MIDI frames
• Oscilloscope
• Demonstrate frequency of sent MIDI
messages
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General Advice
 Consult the Atmega32 datasheet
• Pin layouts
• Code examples in C and assembly
• All the info you need to manipulate the microcontroller
for this project is here!
 Use the AVR studio debugger
• Check the value of pins and registers
• Single step through code to find source of problems
 Use internet resources
• avrfreaks.net is a good resource for examples
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DEMO
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Backup
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AVR Assembly
Commands similar to MIPS
ldi, breq, andi, lsr, rsr, etc.
‘in’/’out’ used when working with I/O ports
Can ‘rjmp’ using tags (no offsets to worry about)
There are some differences though…
sbic, neg, cbi, etc.
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Setup Example (AVR)
Setup Example
.include "m32def.inc“ (Include system
file)
.def Temp=R16
(Define R16 register)
.org 0x0000
(Where to begin)
rjmp RESET
RESET:
…
(Jump to RESET)
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Stack Pointer
You must initialize the stack pointer if you wish to
return from jumps…
Set stack pointer
ldi
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Temp, 0x65
out
SPL, Temp
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Setup Example (C)
Setup Example
#include <avr/io.h>
(Include system file)
int main() {
int data;
DDRA = 0xFF;
(PORTA output)
DDRB = 0x00;
(PORTB input)
PORTA = 0x55;
(Output 0x55 or
0b01010101)
data = PINB;
(Store input values)
}
…
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Timer1
Timer1 is the 16-bit counter on the AVR
Will count overflows of Timer1 in order to
gauge transmission time.
Good to set counter prescalar to 1024
Choose 1024 prescalar for Timer1
ldi
out
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Temp, 0x05
TCCR1B, Temp
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USART
Must initialize with desired baud rate and frame
format
Must be initialized in both C and ASM
MIDI Baud rate : 31.25 kbps
Want start/stop bits and 8 data bits
Read data sheet
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