Microcontrollers Introduction

Aly El-Osery

Electrical Engineering Department New Mexico Institute of Mining and Technology Socorro, New Mexico, USA

January 17, 2019

A microcontroller is a processor with memory and several other components integrated on a a single chip making it perfect for a variety of applications covering a wide range, e.g., coﬀee machines, automotive industry, communications, defense systems, satellites, etc.

Microcontroller Microprocessor

EEPROM/ Timer/ CPU SRAM Flash Counter EEPROM/ Timer/ CPU SRAM Flash Counter

Digital I/O Serial Other Serial Digital I/O ADC ADC module interface peripherals General Purpose interface module Microprocessor Microcontroller

Contains a processor Processor is standalone, memory and I/O Has memory and I/O modules integrated on modules are seperate the same chip Designer can choose components for memory Compact and I/O Cheap High processing power Small power consumption General purpose

68HC11/12 — Freescale Semiconductors’s (Formerly Motorola) 8051 — Intel AVR — Atmel Z8 — Zilog PIC — Microchip

BigAVR6 Dragon12 Plus ATtiny85

Zilog

Control unit performed by a microcontroller is integrated into the system.

Integration for mechanical systems with electronics and information processing.

Capability of meeting the speciﬁcation of the task at hand Speed Packaging Power consumption Amount of memory Number of I/O pins Upgradability Cost Development tools Availability

Complex Instruction Set Computer (CISC) Larger architecture Variable code size Powerful instruction set Requires several clock cycles to execute instructions

Reduced Instruction Set Computer (RISC) Simple architecture Small set of instructions One or few clock cycles to execute instructions

Von Neumann Harvard

Code Data data bus data bus memory memory

Code Data data bus CPU memory control bus control bus memory address bus CPU control bus address bus address bus Harvard architecture Von Neumann architecture

Separate buses for accessing code and Code and data are accessed through the data same bus Faster Results in a bottle neck since we can’t Less delays access code and data at the same time Requires more hardware More delays Overview Choosing a Microcontroller Microcontroller Architectures AVR Microcontroller Atmega1284 Assembly vs C Toolchain Aly El-Osery (NMT) EE 308: Microcontrollers January 17, 2019 10 / 25 AVR Core

RISC with Harvard architecture Code ROM Data RAM Data EEPROM Timers I/O ports ADC PWM Communication interfaces: USART, SPI, I2C (TWI), CAN, USB

RISC architecture 131 instructions (most executes in single clock cycle) 128K bytes code ROM 4K bytes EEPROM 16K bytes SRAM JTAG Timers/counters, PWM, 8-channel 10bit ADC Watchdog timer USART, SPI, I2C

This will be the chip used through out the semester.

More eﬃcient use of computing power and memory Closer to the hardware If mass production is the goal, then there will be money saving by going to smaller cheaper parts

Assembly language consists of, instructions referred to as mnemonics, directives and labels. .INCLUDE "M1284DEF.INC" LDI R16, hi8(RAMEND) OUTSPH, R16 LDI R16, lo8(RAMEND) 5 OUTSPL, R16 ;initialize stack pointer

SBIDDRC, 0 ;set bit0 ofDDRC HERE: SBIPORTC, 0 10 CALLDELAY ;callDELAY subroutine CBIPORTC, 0 CALLDELAY RJMPHERE

15 DELAY: LDI R20, 255 DL1 :DEC R20 BRNE DL1 RET

Assembly language consists of, instructions referred to as mnemonics, directives and labels. .INCLUDE "M1284DEF.INC" Directive LDI R16, hi8(RAMEND) OUTSPH, R16 LDI R16, lo8(RAMEND) 5 OUTSPL, R16 ;initialize stack pointer

SBIDDRC, 0 ;set bit0 ofDDRC HERE: Label SBIPORTC, 0 10 CALLDELAY ;callDELAY subroutine CBIPORTC, 0 CALLDELAY RJMPHERE Comment

15 DELAY: LDI R20, 255 DL1 :DEC R20 Instruction BRNE DL1 RET

GNU AVR toolchain (will be used in lectures) Free Open source Linux and Windows (WinAVR) Arduino IDE is based on it Requires a bit more eﬀort to make it work Atmel Studio (mostly used in the lab) Free Supports all their products Runs only on Windows Has and additional assembler (used by default): avrasm2 Can’t handle mixed C and assembly, and relies on GCC to do that

Assembler — replaces mnemonics by their opcodes, resolves include directives, translates register names to addresses, removes comments, etc. avr-as -mmcu=atmega1284 -o ex.o ex.s

Linker — links multiple ﬁles avr-ld -mavr51 -o ex.elf ex.o

Translate object ﬁles avr-objcopy -j .text -j .data -O ihex -o ex.hex ex.elf

Motorola S19 Intel Hex S01100006578616D706C65345F332E686578C9 :1000000000E40EBF0FEF0DBF389A409A0E940C001B S113000000E40EBF0FEF0DBF389A409A0E940C0017 :1000100040980E940C00F9CF4FEF4A95F1F70895F0 S113001040980E940C00F9CF4FEF4A95F1F70895EC :00000001FF S9030000FC

Start code (:) Record type (2 characters) Byte count data only (2 characters) S0 Block header Address (4 characters) S1-3 Data records Record type (2 characters) S5 Record count 00 data record S7-9 End of block 01 end of ﬁle Byte count (2 characters) Address + Data + Checksum Data (2k characters) Address (4 characters) Checksum (2 characters) Data (2k characters) Checksum (2 characters)

Using Dragon Board avrdude -v -c dragon_jtag -p m1284 -Pusb -U flash:w:ex.hex

Using ArduinoISP avrdude -v -c arduino -p m1284 -Pusb -b 19200 -U flash:w:ex.hex

There are diﬀerences between the GCC assembler and the one used by Atmel. For full list you need to consult the documentation but below are some of the frequently used ones.

avr-as avrasm2 .equ DDRA, 0x01 .equ DDRA = 0x01 .asciz “hello” .db “hello”,0 .section .data .dseg .section .text .cseg hi8 high lo8 low

Interfaces SPI JTAG PDI aWire Full source-level debugging in Atmel Studio Supports ARM Cortex

Prototyping area Programming Interfaces SPI High Voltage Serial Parallel JTAG PDI aWire Debugging Interfaces JTAG debugWIRE PDI aWire

Uses ISP interface Cheap Board can be used as a regular microcontroller

Overview Choosing a Microcontroller Microcontroller Architectures AVR Microcontroller Atmega1284 Assembly vs C Toolchain Aly El-Osery (NMT) EE 308: Microcontrollers January 17, 2019 23 / 25 Makeﬁle

FILENAME = example

MCU = atmega1284 PARTNO = m1284 ARCH = avr51 PORT = usb PROGRAMMER = dragon_jtag

AS = avr-as LD = avr-ld OBJCOPY = avr-objcopy PROG = avrdude

ASFLAGS = -mmcu=$(MCU) --gstabs LDFLAGS = -m$(ARCH) OBJFLAGS = -j .text -j .data -O ihex PRFLAGS = -v -c $(PROGRAMMER) -p $(PARTNO) -P$(PORT)

.PHONY: all install clean

all: $(FILENAME).hex $(FILENAME).o $(FILENAME).elf

%.o: %.s $(AS) $(ASFLAGS) -o $@ $<

%.elf: %.o $(LD) $(LDFLAGS) -o $@ $<

%.hex: %.elf $(OBJCOPY) $(OBJFLAGS) $< $@

install: $(FILENAME).hex $(PROG) $(PRFLAGS) -U flash:w:$<

clean: rm -f $(FILENAME).hex $(FILENAME).elf $(FILENAME).o

Overview Choosing a Microcontroller Microcontroller Architectures AVR Microcontroller Atmega1284 Assembly vs C Toolchain Aly El-Osery (NMT) EE 308: Microcontrollers January 17, 2019 24 / 25 As an engineer, speciﬁcally an embedded systems engineer, you must understand enough about what you are designing, standards and speciﬁcations, and have the ability to validate and verify your design. The Arduino environment may not give you the ability to do so.

Very useful to non-technical users, hobbyists, students (K-12), but highly questionable for critical engineering designs

Arduino environment

Overview Choosing a Microcontroller Microcontroller Architectures AVR Microcontroller Atmega1284 Assembly vs C Toolchain Aly El-Osery (NMT) EE 308: Microcontrollers January 17, 2019 25 / 25 Very useful to non-technical users, hobbyists, students (K-12), but highly questionable for critical engineering designs

Arduino environment

Free package Arduino language implemented in C/C++ Lots of libraries A lot of copy/paste Hides a lot of the details and therefore Makes you lazy Optimization requires extensive redesign of code Resulting code may not operate under strict timing, memory, power requirements As an engineer, speciﬁcally an embedded systems engineer, you must understand enough about what you are designing, standards and speciﬁcations, and have the ability to validate and verify your design. The Arduino environment may not give you the ability to do so.

Very useful to non-technical users, hobbyists, students (K-12), but highly questionable for critical engineering designs

Overview Choosing a Microcontroller Microcontroller Architectures AVR Microcontroller Atmega1284 Assembly vs C Toolchain Aly El-Osery (NMT) EE 308: Microcontrollers January 17, 2019 25 / 25