Microcontroller programming

Better "fit for purpose"

Consider:

• processing power
• memory
• I/O capabilities (+pins number)
• power consumption
• existing libraries / support

From blinking led to linux OS (5G chips) and beyond.

AtTiny (412 / 1614 / 3216 / ...)

• 8 bits - 1MHz-20Mhz (→ 32MHz overclock)
• Versatile I/O (analog, PWM, I²C, UART, SPI, ...)
• Single pin programming (UPDI) = half-duplex serial
• Sandbox board : Adrianino

SAMD (11C, 11D, 21E, D51)

• 32 bits - 48MHz - Single ARM Cortex-M0+
• Native USB support (+CDC +HID)
• Versatile I/O (analog, PWM, I²C, UART, SPI, ...)
• Programming : SWD / JTAG (then bootloader?)
• Sandbox board : Samdino or QPAD21

RP2040 / RP2350 (Xiao or Rpi Pico)

• 32 bits - 48MHz - 133MHz (→ >250MHz overclk)
• Dual ARM Cortex-M0+ / CortexM33 & Hazard3 RISC-V
• Programmable I/O (PIO)
• Hardcoded bootloader (UF2)
• Sandbox board : FabXIAO or QPAD-Xiao

ESP32-C3/S3

• RISC-V - 160MHz
• Wifi - BlueTooth
• Versatile I/O
• Sandbox board : FabXIAO

Others

nRF52840 (Xiao BLE)

STM32 ("Blue Pill"), FabSat (instr. bootcamp 2026)

PIC (Microchip), Pinguino

MSP/TI

...

General rule : RTFM / RTFDatasheet

Always refer to the microcontroller's datasheet and reference manual for detailed specifications and usage instructions. These documents provide essential information for programming and configuring the microcontroller.

• Newbie landing page : RP2040 capable languages
• Pin naming is environment dependent...

Assembly / PIO / VHDL / Verilog

• Direct hardware control
• Efficient but complex to write
• Programmable I/O (PIO) offloads I/O from CPU
• Learn binary/logic basics! (worth it!)

• Efficient & low-level hardware access
• Compiled language (machine code)
• Arduino is C++ based
• Industry standard for embedded systems

• Higher level of abstraction
• Interpreted or precompiled to bytecode
• Easier to learn & fast prototyping
• MicroPython & CircuitPython variants

• Strong safety guarantees
• Modern language features
• Compiled language (like C/C++)
• Growing ecosystem for embedded systems

• Familiar syntax for web developers
• Can run on microcontrollers (Kaluma, Espruino)
• Requires more resources than C
• Good for rapid prototyping

• TinyGo brings Go to microcontrollers
• Supports various MCUs (SAMD, RP2040, ESP32, ...)
• Optimized garbage collector
• Built-in GPIO, I2C, SPI libraries
• Cross-compilation support

• Real-time OS kernel for embedded systems
• FreeRTOS is the most popular open-source RTOS
• Provides task scheduling, synchronization, and memory management
• Supports multi-threading and priority-based scheduling
• Available for most popular MCU platforms

Mixed languages

Mixing languages might give you the best of each world :

• ASM → C → C++
• Micropython + PIO

Mixing microPython and PIO "assembly" on RP2040

AI Programming Assistants

• Makes you faster, not smarter
• Learning : different approaches and patterns
• Never use/execute code you don't fully understand
• Always review and test generated code thoroughly
• Tool to accelerate, not to replace your thinking

Very first algorithm (1843!): conditionnal branching and loop.

Loop : "Infinite" while

Make your code run "forever".

Loop : "conditional" while

Make your code run "as long as"...

Loop : for

Make your code run a specific number of times.

Function Call

Make your code modular by using functions.

Branching : if then else

Code execution based on a condition.

Bootloader : small program stored memory that initialize the µC and load/rewrite code from a secondary storage device such as serial port (USB/UART), flash memory or EEPROM.

Hardcoded bootloader (UF2)

• Hardcoded bootloader : you "can't" brick it
• Appears as a USB mass storage device
• Drag and drop firmware files (UF2 format)

One programmer to rule them all

Basic board for using Alex Tardov's Free DAP

Know the differences:

• Arduino board = hardware platform
• Arduino libraries = set of functions
• Arduino IDE = development environment

All three are distinct but commonly used together

Arduino Uno = board = hardware

• Specific hardware board with ATmega328P (outdated!) microcontroller
• One of the most commonly used Arduino boards
• Popular for prototyping and educational purposes

Arduino is a set of libraries

• Simplifies common tasks: analog inputs, digital outputs, peripherals
• Abstracts register details for easier coding
• Provides portable code across various chips
• Trade-off: generated code is usually less efficient

"Pure C" VS Arduino

• AtTiny : Spence Konde
• SAMD : MattairTech. Fork Fab maintainted (QB fork)
• Rp2040 : Earle F. Philhower porting
• ESP32 : Espressif
• ...

Arduino IDE is a development environment

• Writing, compiling, and uploading code
• Syntax highlighting, serial monitor+plotter, library management, boards management
• Available in v1 and v2 versions
• IDE v2: better editor but may have compatibility issues

Document your code (as you go...)

• Every programming language has special "commented" code sections
• Comments explain your logic and reasoning
• Makes code easier to understand and maintain
• Future you (and others) will thank present you

Write modular and readable

• Break code into modular components for better readability
• Organize into separate functions/modules by functionality
• Facilitates debugging and future updates
• Flat files are difficult to modify and maintain

Modular writing

Write "parametric"

• Avoid hardcoding constants directly into code
• Use symbolic names or macros with const/#define
• Improves code clarity and readability
• Allows easier modifications in the future

Parametric : Example

Parametric : Example

Use Classes / Objects / Libraries

• Allows you to "think as objects"
• Is called "object oriented" (C++ vs C)
• Widely used by Arduino hardware specific libraries

Classes

Simulate your circuit

• Use simulators to test and debug your code before deploying on hardware
• Wokwi (PIO!), Tinkercad, Proteus, etc.
• Save time and prevent damage to hardware

Optimizations

Some tips :

• lookup tables (vs complex maths)
• inline
• pointers
• "simple" arithmetics : 2ⁿ divisions = >>
• Proper type : uint8_t, int16_t, etc. (pecularly on 8bits proc)
• ...

Fit-for-purpose processor

• Select microcontroller wisely
• Consider underclocking and sleep for power-sensitive projects
• Underclocking can be as useful as overclocking!
• Power (instr. bootcamp 2026)

Reduce Power Consumption

• Power consumption is critical for battery-powered and remote devices
• Multiple strategies available to optimize energy usage
• Different approaches suitable for different applications
• Combine multiple techniques for best results

Strategy 1: Underclocking

• Reduce CPU clock frequency for lower power consumption
• Lower frequency = lower power (linear)
• Example: 1 MHz instead of 20 MHz = 95% savings!

Strategy 2: Disable Unused Peripherals

• Each peripheral (ADC, UART, SPI, ...) consumes power when enabled
• Disable peripherals not used in your application
• Avoid "floating" pins
• Can disable at init or dynamically during runtime

Strategy 3: Sleep Modes & Interrupts

• Microcontrollers "Inception" : multiple sleep states (idle, light, deep, hibernation)
• Use interrupts to wake when needed
• Extremely effective for event-driven applications

Practical Power Optimization

• Start with sleep modes for maximum impact
• Add peripheral disabling for fine-tuning
• Consider underclocking
• Profile your code to identify power hotspots
• Use oscilloscope/power meter to verify improvements

Write down what you do

The Pragmatic Programmer

Talk to me

Narrowing down the problem

• Reproduce the problem

• Reproduce the problem
• Always first do visual check

• Reproduce the problem
• Always first do visual check
traces
soldering
components

• Reproduce the problem
• Always first do visual check
traces
soldering
components
• Keep in mind that the problem
  might not be visible without a microscope

4. Keep in Mind: The Problem May Not Always Be Visible

Isolate the possible problem

Multimeter

Continuity

• Test power supply to power pins continuity
• Check fuses, diodes orientations, ...
• Check short-circuits
• Check traces

• Parallel measurement => check your cables!
• ! absolute maximum ratings (may burn your component)
• Power supply impedence / max power, badly selected
• GND/VCC loop

Continuity

Voltage drop

Logic Analyzer

Logic Analayzer

• "logic analyzer 8 channel"
• "logic analyzer 16 channel"
• "Digikey 461-1010-ND: MICRO-HOOK RED 0.025" SQ PINS"
• "Digikey 461-1010-ND: MICRO-HOOK BLACK 0.025" SQ PINS"

Miniware LA104

LA104 and alternative firmware and apps

Oscilloscope

Radio communications

Flashing your board

USB

SWD/JTag

UPDI

Unified Program and Debug Interface

Serial (or any) "Hello world!"

#define DEBUG_MODE 1
        ...
#if DEBUG_MODE
         Serial.print("DEBUG -- MyVal value = ");
        Serial.println(MyVal, DEC);
#endif