42Chips_Piscine_Embedded

Demos

Videos

Module 0

M00-04.mp4

M00-03.mp4

M00-02.mp4

M00-01.mp4

Module 1

M01-03.mp4

M01-02.mp4

M01-01.mp4

M01-00.mp4

Module 2

M02-04.mp4

M02-03.mp4

M02-02.mp4

M02-01.mp4

M02-00.mp4

Module 3

M03-03.mp4

M03-02.mp4

M03-01.mp4

M03-00.mp4

Module 4

M04-01.mp4

M04-00.mp4

Module 5

M05-04.mp4

M05-03.mp4

M05-02.mp4

M05-01.mp4

M05-00.mp4

Module 6

M06-02.mp4

M06-01.mp4

M06-00.mp4

Resources

• AVR-Microcontroller-ATmega328P
  • ATmega328P - Summary
  • Interrupt Vectors Table
• Calculator

Config

VSCode

• [C/C++ Config]
  • Extension (ms-vscode.cpptools)

  @ext:ms-vscode.cpptools
  

  • c_cpp_properties.json

  {
    "configurations": [
      {
        "name": "linux-avr-gcc",
        "includePath": ["${workspaceFolder}/**", "/usr/lib/avr/include/**"],
        "defines": [],
        "mergeConfigurations": false,
        "compilerPath": "/usr/bin/avr-gcc",
        "cStandard": "gnu11",
        "cppStandard": "gnu++17",
        "intelliSenseMode": "linux-gcc-x64",
        "compilerArgs": ["-mmcu=atmega328p", "-DF_CPU=16000000UL", "-Os"],
        "browse": {
          "path": ["${workspaceFolder}"],
          "limitSymbolsToIncludedHeaders": true
        }
      }
    ],
    "version": 4
  }

Information

AVR

• AVR Programming

• AVR stands for Alf and Vegard's RISC processor

• avr-gcc is a compiler that takes C code and turns it into machine code that the AVR microcontroller can execute

  • mmcu=atmega328p specifies the microcontroller model
  • -Os optimizes the code for size
  • -DF_CPU=16000000UL specifies the clock speed of the microcontroller
  • -o specifies the output file

flowchart LR
    subgraph ELF["ELF File (.elf)"]
        direction TB
        E1["• Machine Code
        • Debug Info
        • Symbol Tables
        • Relocation Data"]
    end

    subgraph Process["Conversion Process"]
        direction TB
        P1["avr-objcopy
        -O ihex
        -R .eeprom"]
    end

    subgraph HEX["HEX File (.hex)"]
        direction TB
        H1["• Pure Binary Code
        • Memory Addresses
        • Program Data Only"]
    end

    ELF --> Process --> HEX

    style ELF fill:#e6f3ff,stroke:#333,stroke-width:2px,color:#000000
    style Process fill:#fff,stroke:#333,stroke-width:2px,color:#000000
    style HEX fill:#f5f5f5,stroke:#333,stroke-width:2px,color:#000000

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• ELF (Executable and Linkable Format) is a standard file format for executables, object code, shared libraries, and core dumps
• HEX (Intel Hexadecimal Object File Format) is a file format that conveys binary information in ASCII text form
• avr-objcopy is a utility program that copies only the parts of the object files that are needed
  • -O ihex specifies the output format as Intel HEX
  • -R .eeprom removes the EEPROM data from the HEX file
    • EEPROM (Electrically Erasable Programmable Read-Only Memory) is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed
• avrdude is a utility program that ahttps://www.rapidtables.com/convert/number/decimal-to-binary.html?x=16

AVR Libraries

AVR I/O

• avr/io.h is a library that provides access to the I/O registers of the AVR microcontroller
• I/O registers are memory locations that control the behavior of the microcontroller
  • I/O registers are used to configure the pins of the microcontroller as inputs or outputs, read the state of the pins, and write data to the pins

flowchart LR
    classDef main fill:#1976d2,stroke:#01579b,stroke-width:2px,color:#ffffff
    classDef included fill:#6a1b9a,stroke:#4a148c,stroke-width:2px,color:#ffffff
    classDef purpose fill:#ffffff,stroke:#616161,stroke-width:1px,color:#000000,text-align:left

    io["<b>avr/io.h</b><br/><i>Main Header File</i>"]:::main

    subgraph Included_Files["Included Components"]
        direction TB
        sfr["<b>sfr_defs.h</b><br/>Special Function Registers"]:::included
        pins["<b>portpins.h</b><br/>Port Pin Definitions"]:::included
        common["<b>common.h</b><br/>Common Register Names"]:::included
        version["<b>version.h</b><br/>Version Information"]:::included
    end

    subgraph Purposes["Key Functions"]
        direction TB
        reg["Register Access<br/>• Direct register manipulation<br/>• Bit-level operations"]:::purpose
        def["Definitions<br/>• Device-specific mappings<br/>• Interrupt handling"]:::purpose
        prot["Protection<br/>• CCP mechanism support<br/>• Protected register writes"]:::purpose
    end

    io --> Included_Files
    io --> Purposes

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AVR I/O Registers

IO Ports

Register	Description	Address	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
DDRx	Data Direction Register	0x0A	D7	D6	D5	D4	D3	D2	D1	D0
PORTx	Port Output Register	0x0B	P7	P6	P5	P4	P3	P2	P1	P0
PINx	Port Input Register	0x09	I7	I6	I5	I4	I3	I2	I1	I0

flowchart LR
    subgraph "Port Configuration"
        DDR["DDRx Register<br/><i>Direction Control</i><br/>0 = Input<br/>1 = Output"]
    end

    subgraph "Output Control"
        PORT["PORTx Register<br/><i>Output Driver</i><br/>0 = Low Level<br/>1 = High Level"]
    end

    subgraph "Pin Monitoring"
        PIN["PINx Register<br/><i>Physical Pin State</i><br/>Read-only"]
    end

    DDR --> |"Controls"| PORT
    PORT --> |"Drives"| PIN
    PIN --> |"Reflects"| PIN

    style DDR fill:#ffcdd2,stroke:#c62828,color:#000000
    style PORT fill:#bbdefb,stroke:#1976d2,color:#000000
    style PIN fill:#c8e6c9,stroke:#388e3c,color:#000000

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• DDRx (Data Direction Register)
  • Controls whether each pin acts as input (0) or output (1)
  • Bit n controls pin n (e.g., DDRB0 controls PORTB0)
  • Writing 1 sets the corresponding pin as output
  • Writing 0 sets the corresponding pin as input
• PORTx (Port Register)
  • Controls the output value when a pin is configured as output
  • Can also enable/disable internal pull-up resistors for input pins
  • Bit n controls the output driver for pin n
• PINx (Pin Register)
  • Read-only register showing actual pin states
  • Always reflects the physical state of the pins
  • Bit n reads the state of pin n

DDR-PORT-PIN

AVR Timers

• Timers are used to generate precise time delays, measure time intervals, and control the frequency of waveforms
• Timers are implemented using Timer/Counter Registers
  • Timer/Counter Registers are memory locations that control the behavior of the timers
  • Timer/Counter Registers are used to configure the timers, read the current count value, and write new count values

Timer/Counter Registers

Register	Description	Address	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
TCCRnA	Timer/Counter Control Reg A	0x2n	COMnA1	COMnA0	COMnB1	COMnB0	-	-	WGMn1	WGMn0
TCCRnB	Timer/Counter Control Reg B	0x2n+1	FOCnA	FOCnB	-	-	WGMn2	CSn2	CSn1	CSn0
TCNTn	Timer/Counter Register	0x2n+2	TCNTn7	TCNTn6	TCNTn5	TCNTn4	TCNTn3	TCNTn2	TCNTn1	TCNTn0
OCRnA	Output Compare Reg A	0x2n+3	OCRnA7	OCRnA6	OCRnA5	OCRnA4	OCRnA3	OCRnA2	OCRnA1	OCRnA0
OCRnB	Output Compare Reg B	0x2n+4	OCRnB7	OCRnB6	OCRnB5	OCRnB4	OCRnB3	OCRnB2	OCRnB1	OCRnB0
ICRn	Input Capture Register	0x2n+4	ICRn7	ICRn6	ICRn5	ICRn4	ICRn3	ICRn2	ICRn1	ICRn0
TIFRn	Timer/Counter Interrupt Flag	0x3n	-	-	-	-	-	-	OCFnA	OCFnB

• n is the timer number (e.g., Timer0, Timer1, Timer2)
• COMnA1 and COMnA0 control the output behavior of the OCnA pin
• COMnB1 and COMnB0 control the output behavior of the OCnB pin
• WGMn2, WGMn1, and WGMn0 control the waveform generation mode
• FOCnA and FOCnB are used to force an output compare match
• CSn2, CSn1, and CSn0 control the clock source
• TCNTn is the timer/counter register that holds the current count value
• OCRnA and OCRnB are the output compare registers that hold the comparison values
• ICRn is the input capture register that holds the capture value
• OCFnA and OCFnB are the output compare match flags

Prescaler

• The prescaler is a counter that divides the clock frequency before it reaches the timer

• The prescaler is used to reduce the clock frequency to a manageable level

  • This allows the timer to count at a slower rate
  • This prevents the timer from overflowing too quickly
    • Example: Timer1 is an 16-bit counter that can count up to $2^{16} = 65,536$
      • $F_{timer} = \frac{System\ clock}{Prescaler}$
      • $F_{timer} = \frac{16\ \text{MHz}}{1024} = 15.625\ \text{KHz}$
      • $T_{tick} = \frac{1}{15.625\ \text{KHz}} = 64\ \mu s$
      • $T_{total} = 64\mu s \times 65,536 = 4.194\ \text{s}$
      • The timer will overflow every 4.194 seconds

• The prescaler is controlled by the CSn2, CSn1, and CSn0 bits in the TCCRnB register

CSn2	CSn1	CSn0	Prescaler	Description
0	0	0	0	No prescaling
0	0	0	1	$clk_{I/O}$
0	0	1	8	$clk_{I/O}$/8
0	1	0	64	$clk_{I/O}$/64
0	1	1	256	$clk_{I/O}$/256
1	0	0	1024	$clk_{I/O}$/1024

flowchart TB
    subgraph "Timer Configuration"
        TCCR["TCCRnA/B Registers<br/><i>Control Settings</i>"]
    end

    subgraph "Timer Counter"
        TCNT["TCNTn Register<br/><i>Counter Value</i>"]
    end

    subgraph "Output Compare"
        OCR["OCRnA/B Registers<br/><i>Comparison Value</i>"]
    end

    subgraph "Input Capture"
        ICR["ICRn Register<br/><i>Capture Value</i>"]
    end

    subgraph "Interrupt Flags"
        TIFR["TIFRn Register<br/><i>Interrupt Flags</i>"]
    end

    TCCR --> |"Control"| TCNT
    TCCR --> |"Control"| OCR
    TCCR --> |"Control"| ICR
    TCCR --> |"Control"| TIFR

    style TCCR fill:#ffcdd2,stroke:#c62828,color:#000000
    style TCNT fill:#bbdefb,stroke:#1976d2,color:#000000
    style OCR fill:#c8e6c9,stroke:#388e3c,color:#000000
    style ICR fill:#dcedc8,stroke:#689f38,color:#000000
    style TIFR fill:#f0f4c3,stroke:#afb42b,color:#000000

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Waveform Generation Modes

• The waveform generation mode is controlled by the WGMn2, WGMn1 , and WGMn0 bits in the TCCRnA and TCCRnB registers
• The waveform generation mode determines how the timer counts and when it overflows
• There are several waveform generation modes available
  • Normal Mode
  • CTC (Clear Timer on Compare Match) Mode
  • Fast PWM Mode
  • Phase Correct PWM Mode
• PWM: Pulse Width Modulation
  • PWM is a technique used to generate analog-like signals using digital outputs
  • The frequency of the signal is controlled by changing the period of the pulse

flowchart TB
    subgraph "Waveform Generation Modes"
        WGM["WGMn2/1/0 Bits<br/><i>Waveform Mode</i>"]
    end

    subgraph "Normal Mode"
        NM["Normal Mode<br/><i>Overflow at MAX</i>"]
    end

    subgraph "CTC Mode"
        CTC["CTC Mode<br/><i>Clear on Compare Match</i>"]
    end

    subgraph "Fast PWM Mode"
        FPM["Fast PWM Mode<br/><i>Non-inverting</i>"]
    end

    subgraph "Phase Correct PWM Mode"
        PCP["Phase Correct PWM Mode<br/><i>Symmetrical</i>"]
    end

    WGM --> |"Control"| NM
    WGM --> |"Control"| CTC
    WGM --> |"Control"| FPM
    WGM --> |"Control"| PCP

    style WGM fill:#ffcdd2,stroke:#c62828,color:#000000
    style NM fill:#bbdefb,stroke:#1976d2,color:#000000
    style CTC fill:#c8e6c9,stroke:#388e3c,color:#000000
    style FPM fill:#dcedc8,stroke:#689f38,color:#000000
    style PCP fill:#f0f4c3,stroke:#afb42b,color:#000000

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• Normal Mode
  • The timer counts from 0 to 255 (8-bit) or 65,535 (16-bit) and then overflows
  • The timer overflows when it reaches the maximum count value
  • The timer is reset to 0 after overflowing
• CTC Mode
  • The timer counts from 0 to a comparison value and then resets
  • The timer resets when it reaches the comparison value
  • The timer is reset to 0 after resetting
• Fast PWM Mode
  • The timer counts from 0 to 255 (8-bit) or 65,535 (16-bit) and then overflows
  • The timer overflows when it reaches the maximum count value
  • The timer is reset to 0 after overflowing
  • The output pin is set high when the timer is less than the comparison value
  • The output pin is set low when the timer is greater than the comparison value
• Phase Correct PWM Mode
  • The timer counts up to the comparison value and then counts down to 0
  • The timer counts up when the timer is less than the comparison value
  • The timer counts down when the timer is greater than the comparison value
  • The output pin is set high when the timer is less than the comparison value
  • The output pin is set low when the timer is greater than the comparison value

UART Protocol

• UART - Wiki
• UART - Understanding

• UART (Universal Asynchronous Receiver/Transmitter) is a serial communication protocol used to transfer data between devices
• UART is asynchronous, meaning that the data is transmitted without a clock signal
• UART uses two pins: TX (Transmit) and RX (Receive)
• UART data is transmitted one bit at a time, starting with the least significant bit (LSB)
• UART data is transmitted in frames, with each frame consisting of a start bit, data bits, parity bit, and stop bit

---
title: UART Frame
bitsPerWidth: 12
---
packet-beta
0-1: "(Idle)"
2: "St"
3: '0'
4: '1'
5: '2'
6: '3'
7: '4'
8: '5'
9: '[6]'
10: '[7]'
11: '[8]'
12: '[P]'
13: 'Sp'
14: '[Sp]'
15-16: 'St/Idle'

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• The start bit signals the beginning of the frame (always 0)
• The data bits contain the actual data being transmitted
• The parity bit is used for error checking (even, odd, or none)
• The stop bit signals the end of the frame (always 1)

• The baud rate is important for UART communication
  • The baud rate is the number of bits transmitted per second
  • The baud rate determines the speed of the communication
  • The baud rate must be the same on both the transmitter and receiver
• The baud rate is calculated as follows:
  • $Baud\ Rate = \frac{Clock\ Frequency}{16 \times (UBRRn + 1)}$
  • $UBRRn = \frac{Clock\ Frequency}{16 \times Baud\ Rate} - 1$
    • $UBRRn$ is the UART Baud Rate Register

AVR Interrupts

• Interrupts - AVR
• An interrupt is a signal that informs the microcontroller that a specific event has occurred
• Interrupts allow the microcontroller to respond to external events in real-time

Types of Interrupts

• External Interrupts
  • External interrupts are triggered by external events
  • External interrupts can be triggered by changes on specific pins
  • External interrupts can be used to wake the microcontroller from sleep mode
• Timer Interrupts
  • Timer interrupts are triggered by timer events
  • Timer interrupts can be used to generate precise time delays
  • Timer interrupts can be used to control the frequency of waveforms
• USART Interrupts
  • USART interrupts are triggered by UART events
  • USART interrupts can be used to handle incoming and outgoing data
  • USART interrupts can be used to implement a serial communication protocol

Interrupt Vector Table

• The interrupt vector table is a table of addresses that point to the interrupt service routines (ISRs)
• The interrupt vector table is located at the beginning of the program memory

Interrupt Vectors Table

Vector	Address	Code	Description
0	0x0000	RESET	Reset
1	0x0002	INT0	External Interrupt 0
2	0x0004	INT1	External Interrupt 1
3	0x0006	INT2	External Interrupt 2
...	...	...	...
17	0x0012	TIMER0_OVF	Timer/Counter0 Overflow
...	...	...	...

Enabling Interrupts

• To enable interrupts, the Global Interrupt Enable (I) bit in the Status Register (SREG) must be set

#include <avr/interrupt.h>

int main(void) {
    sei(); // Enable global interrupts
    ...
}

• To enable a specific interrupt, the Interrupt Enable (IEn) bit in the Interrupt Mask Register (pIMSK) must be set

#include <avr/interrupt.h>

int main(void) {
    TIMSK |= (1 << TOIE0); // Enable Timer/Counter0 Overflow Interrupt
    ...
}

• To disable a specific interrupt, the Interrupt Enable (IEn) bit in the Interrupt Mask Register (pIMSK) must be cleared

#include <avr/interrupt.h>

int main(void) {
    TIMSK &= ~(1 << TOIE0); // Disable Timer/Counter0 Overflow Interrupt
    ...
}

Interrupt Service Routines

• An Interrupt Service Routine (ISR) is a function that is called when an interrupt occurs
  • The ISR is executed in response to the interrupt
• The ISR must be defined using the ISR macro
  • The ISR macro specifies the vector name for the interrupt

#include <avr/interrupt.h>

ISR(TIMER0_OVF_vect) {
    // Timer/Counter0 Overflow Interrupt
    ...
}

• The ISR macro is used to define an ISR
  • Example: The TIMER0_OVF_vect is the vector name for the Timer/Counter0 Overflow Interrupt

AVR Analog-to-Digital Converter (ADC)

References:

• ADC - Wiki
• ADC - AVR

Infos:

• The Analog-to-Digital Converter (ADC) is used to convert analog signals into digital values
• The ADC is used to measure analog signals from sensors, transducers, and other devices
• The ADC converts the analog signal into a digital value that can be processed by the microcontroller

I2C Protocol

• I2C - Wiki
• I2C - Introduction - Circuitbasics

Infos:

• I2C (Inter-Integrated Circuit) is a serial communication protocol used to transfer data between devices
• I2C is a two-wire bus protocol that uses a clock signal (SCL) and a data signal (SDA)
  • SCL: Serial Clock Line
  • SDA: Serial Data Line
• I2C is a master-slave protocol where the master device initiates the communication
• I2C devices are connected in a multi-master configuration, allowing multiple devices to communicate on the same bus

I2C communication follows a specific protocol structure:

• Message Structure:
  • Messages begin with a START condition
  • Include an address frame identifying the target device
  • Contain data frames (8 bits each)
  • End with a STOP condition
• Data Transfer Process:
  • Master devices control the clock signal (SCL)
  • Slave devices respond to their addresses
  • Each byte transfer includes acknowledgment (ACK/NACK)
  • Multiple bytes can be transferred in a single message

Advantages:

• Minimal wiring requirements (only two wires needed)
• Support for multiple devices on the same bus
• Flexible addressing system (7-bit or 10-bit)
• Low hardware overhead
• Bidirectional communication capability

Limitations:

• Limited speed compared to other protocols like SPI
• Restricted bus length due to capacitance limitations
• Potential bus contention issues with multiple masters
• Requires proper pull-up resistor configuration

Logic Gates

• Logic Gate
• Logic Gate - Simulator

Flip-Flop

• Flip-Flop - Wiki

• Flip-Flop - Detailled - T,D,JK

• JK Flip-Flop

  • Truth table:

    J	K	Q(t)	Q(t+1)	Comment
    0	0	Q	Q	No change
    0	1	Q	0	Reset
    1	0	Q	1	Set
    1	1	Q	!Q	Toggle

• T Flip-Flop

  • Truth table:

    T	Q(t)	Q(t+1)	Comment
    0	Q	Q	No change
    1	Q	!Q	Toggle

• D Flip-Flop

  • Truth table:

    D	Q(t)	Q(t+1)	Comment
    0	Q	0	Reset
    1	Q	1	Set

Bitwise Operations

BitWise op in embedded programming

Operation	Symbol	Purpose	Description	Example
AND	&	Compare bits	returns 1 if both bits are 1	1010 & 1100 = 1000
OR	|	Set bits	returns 1 if any bit is 1	1010 | 1100 = 1110
XOR	^	Toggle bits	returns 1 if bits are different	1010 ^ 1100 = 0110
NOT	~	Invert bits	returns 1 if bit is 0	~1010 = 0101
Left Shift	<<	Multiply by power of 2	moves bits to the left	1010 << 1 = 10100
Right Shift	>>	Divide by power of 2	moves bits to the right	1010 >> 1 = 0101

Bit manipulation

Pattern	Description	Example
1 << n	Mask Set bit n	n = 3 1 << 3 = 00001000
~(1 << n)	Mask Clear bit n	n = 3 ~(1 << 3) = 11110111
x & (1 << n)	Check bit n	x = 1010 n = 3 x & (1 << 3) 1010 & 1000 = 1000
x | (1 << n)	Set bit n	x = 1010 n = 2 x | (1 << 2) 1010 | 0100 = 1110
x & ~(1 << n)	Clear bit n	x = 1010 n = 1 x & ~(1 << 1) 1010 & 1101 = 1000
x ^ (1 << n)	Toggle bit n	x = 1010 n = 1 x ^ (1 << 1) 1010 ^ 0010 = 1000
x & ((1 << n) - 1)	Clear bits above n	x = 1110 n = 2 x & ((1 << 2) - 1) 1110 & (0100 - 1) = 1110 & 0011 = 0010
x & ~((1 << n) - 1)	Clear bits below n	x & ~((1 << 3) - 1)
x & ((1 << (n + 1)) - 1)	Clear bits above and including n	x & ((1 << (3 + 1)) - 1)
x & ~((1 << (n + 1)) - 1)	Clear bits below and including n	x & ~((1 << (3 + 1)) - 1)

Modules

Module 00

• Info - AVR Programming

• Find the USB port

  # List all USB devices
  lsusb
  
  # List all USB serial devices
  ls /dev/ttyUSB*
  
  # Show detailed device information
  dmesg | grep tty

• Include the necessary libraries <avr/io.h>

• PB0 is the LED pin here (same search for other pins)

  • ICP1/CLKO/PCINT0 – Port B, Bit 0
  • ICP1: Input Capture Pin. The PB0 pin can act as an Input Capture Pin for Timer/Counter1.
  • CLKO: Divided System Clock. The divided system clock can be output on the PB0 pin. The divided system clock will be output if the CKOUT Fuse is programmed, regardless of the PORTB0 and DDB0 settings. It will also be output during reset.
  • PCINT0: Pin Change Interrupt source 0. The PB0 pin can serve as an external interrupt source.
  • 📑 : Atmel ATmega328/P [DATASHEET] Atmel-42735B-ATmega328/P_Datasheet_Complete-11/2016 page 106)

Module 01

Infos about frequency and time:

• 1Hz = 1s = 1000ms
  • 1kHz = 1,000Hz = 1ms
  • 1MHz = 1,000,000Hz = 1µs
• 1 tick = One cycle of the system clock
  • For a 16MHz Clock = 16,000,000 ticks per second
  • 1 tick = 1 / 16,000,000 seconds = 0.0625µs = 62.5ns
  • 1 tick = around 1-2 instructions
• Clock counter
  • Different counters have different maximum values
    • 8-bit counter = 256 ticks
    • 16-bit counter = 65,536 ticks
  • So using prescaling is important to avoid overflow
• Prescaling: Allow to skip a certain number of ticks
  • Prescaler values: 1, 8, 64, 256, 1024 (AVR Microcontrollers)
  • Example:
    • 16MHz / 1 = 16,000,000Hz = 62.5ns
    • 16MHz / 8 = 2,000,000Hz = 0.5µs
    • 16MHz / 64 = 250,000Hz = 4µs
    • 16MHz / 256 = 62,500Hz = 16µs
    • 16MHz / 1024 = 15,625Hz = 64µs

Delay in code :

• Microcontrollers - Timers Counters - Instructables

• Builtin AVR Functions - GNU GCC Docs

• __builtin_avr_delay_cycles

  • void __builtin_avr_delay_cycles (uint32_t ticks)
  • Delays the specified number of CPU cycles.
  • The delay parameter must be a compile-time constant.

Timer registers:

• AVR - Timer programming - ExploreEmbedded

• LED at 1Hz = 1s (0.5s ON, 0.5s OFF)

  • $F_{timer} = \frac{F_{CPU}}{Prescaler}$
  • $F_{timer} = \frac{16\ \text{MHz}}{1024} = 15.625\ \text{KHz}$
  • $T_{tick} = \frac{1}{15.625\ \text{KHz}} = 64\ \mu s$
  • $Cycles/Count = \frac{Wait\ Time}{T_{tick}} = \frac{1\ s}{64\ \mu s} = 15625$
  • $Cycles/Count = \frac{Wait\ Time}{T_{tick}} = \frac{0.5\ s}{64\ \mu s} = 7812.5$

• Duty Cycle

  • Pulse Width(PW) to Total period (T) of the Waveform/Signal
    • Generally expressed in percentage
    • Represents the amount of time the signal is high(1) compared to the total time
  • $Duty\ Cycle = \frac{PW}{T} $
  • $Duty\ Cycle = \frac{ON\ Time}{Total\ Time} = \frac{ON\ Time}{ON\ Time + OFF\ Time}$
    • $Duty\ Cycle = \frac{1\ s}{1\ s + 1\ s} = 50\ %$

• $F_{desired} = \frac{F_{CPU}}{Prescaler \times (1 + TOP)}$

  • $TOP = \frac{F_{CPU}}{F_{desired} \times Prescaler} - 1$
  • $TOP = \frac{16\ \text{MHz}}{1\ \text{Hz} \times 1024} - 1 = 15624$
    • $-1$ because the counter starts from 0

Module02: UART Protocol

# Screen : is a full-screen window manager that multiplexes a physical terminal between several processes
# Listen to the serial port (ttyUSB0) with baud rate 115200
screen /dev/ttyUSB0 115200

# Kill the screen session
Ctrl + A + K

# Detach the screen session
Ctrl + A + D

# List available sessions
screen -ls

# Reattach to a session (if only one exists)
screen -r

# Reattach to a specific session
screen -r session_id

# Kill a specific session
screen -X -S session_id quit

UART - AVR - Guide for use UART - AVR - Interrupts

Ex01: Transmitting

Module03: AVR Timers

Module04: AVR Interrupts

Module05: AVR ADC

• $ADC = \frac{V_{in} \times 1024}{V_{ref}}$

  • $V_{in}$: Input Voltage
  • $V_{ref}$: Reference Voltage
  • $1024$: Resolution (10-bit ADC: $2^{10} = 1024$)

• Atmega328p - Internal Temperature - datasheet

Module06: I2C Protocol

flowchart LR
    subgraph MCU["ATmega328P (Master)"]
        direction TB
        M_SDA["SDA (PC4)"]
        M_SCL["SCL (PC5)"]
        M_GND["GND"]
        M_VCC["VCC (5V)"]
    end

    subgraph Sensor["AHT20 (Slave)"]
        direction TB
        S_SDA["SDA"]
        S_SCL["SCL"]
        S_GND["GND"]
        S_VIN["VIN (2.2-5.5V)"]
    end

    M_SDA -->|"I2C Data"| S_SDA
    M_SCL -->|"I2C Clock"| S_SCL
    M_GND --- S_GND
    M_VCC -->|"Power"| S_VIN

    style MCU fill:#f96,stroke:#333,color:#000
    style Sensor fill:#69f,stroke:#333,color:#fff

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• $F_{SCL} = \frac{F_{CPU}}{16 + 2 \times TWBR \times Prescaler}$

  • $TWBR = \text{Value in TW Bit Rate Register}$
  • $TWBR = \frac{(F_{CPU} / F_{SCL}) - 16}{2 \times Prescaler}$

• I2C - AHT20 - Datasheet - Recommanded section 7.4

• $RH = (\frac{S_{RH}}{2^{20}}) \times 100 \text{ %}$
  • $S_{RH}$: Signal Relative Humidity Value
• $T = (\frac{S_{T}}{2^{20}}) \times 200 - 50 \text{ °C}$
  • $S_{T}$: Signal Temperature Value