Resources for Embedded Development

Nano Waveform Generator Versatile low-cost audio signal generator and pulse generator (up to 4MHz) based on Arduino Nano MCU module.

Touch-sense on any micro-controller Add touch-pads to an MCU without any special on-chip wizardry.

AVR Boards for Embedded Development Designs for starter kits to learn AVR embedded C programming.

Embedded C Programming Tutorial  with coding examples to run on various AVR dev boards

Graphics Function Library for Monochrome LCD Module 128x64 pixels, using KS0108, ST7920 or SH1106 controller

Generalised User Interface for Embedded Applications using graphics LCD module and a cluster of push-buttons

Digital Audio (PCM) Sound Effects Software and audio player for embedded micro-controller applications

ATmega32U4 MCU Peripheral Function Library for use with Microchip/Atmel Studio IDE -- not Arduino!

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Waveform generators, also known as “function generators”, have been popular DIY projects since the beginning of hobby electronics. There are numerous designs out there offering a broad range of functional features and design complexities. The “Nano” waveform generator sits near the low end of complexity and build cost in the hardware design.  However, it packs a lot of punch into an 8-bit AVR micro-controller to produce a useful instrument for testing audio and low-speed digital equipment.

_  Published in Elektor Magazine, Nov-Dec 2023

View/Download Design & Contruction Notes

Download Firmware Development Kit (source code, hex file, project files)

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Some MCU devices provide “automatic” measurement of capacitance between an I/O pin and earth (GND) to facilitate touch-pad sensing. However, a change in capacitance on an input pin can be detected quite easily without any special on-chip wizardry. The technique described in this note uses only one resistor and diode for each touch-pad input. The software algorithm is short, ensuring minimal processing overhead.

Published in Elektor 'Circuit Special', August 2024

View/download article

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Building your own micro-controller development board will not only improve your workshop skills, but the completed product will serve well as a hardware platform for learning embedded programming skills.

The "AVR-BED" is based on Atmel’s ATmega88PA microcontroller. An ATmega328P (as in Arduino Uno R3 and Nano boards) may be substituted if more memory is needed. The board incorporates a 2-line x 16-character LCD module, some LEDs, 4 push-buttons and a potentiometer providing a 0..5V analog signal source.

To make construction even simpler, an alternative design is based on the Arduino Nano board (v3). 
The Nano board replaces many components on the AVR-BED, including the MCU (ATmega328P), USB-serial bridge, ISP programming port and Reset button. This design greatly reduces the number of hook-up wires needed to be soldered on the underside of the board.

AVR-BED original design (v1)

AVR-BED "Nano" alternative build (v2)

The download pack contains detailed design and construction notes, a peripheral function library, plus a "test and demo" program. Sample code was developed with AVR GCC under Microchip/Atmel Studio IDE (v7).

Download AVR-BED Distribution Pack (zip)

How to load program code into an Arduino Nano (or Uno R3) board without Arduino IDE

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Embedded C Programming Tutorial for novices

Here is a self-study tutorial intended as a first course in embedded microcontroller programming using a sub-set of the C language called “C-less” (C language essentials). C-less was conceived to provide enough of C to develop “real-world” applications, while avoiding unnecessary complex constructs which novices might find overwhelming.

The software development environment used in this tutorial is Microchip/Atmel Studio IDE for AVR and SAM Devices. This is a free download from Microchip’s website.

Coding examples are written for Atmel 8-bit AVR microcontroller devices, specifically the ATmega88PA or ATmega328P, as fitted on the author’s “AVR-BED” and “Nano-BED” development platforms. Compatible hardware platforms can be built around Arduino Uno or Microchip AVR 'X-mini' boards.

The Tutorial has a companion "C-less Reference Manual".

View/Download AVR Embedded C Tutorial

View/Download  C-less Reference Manual

Download Tutorial Example Programs

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Graphics Function "Library" for Monochrome LCD and OLED Modules

This software package is designed for monochrome (1 bit-per-pixel) graphics LCD modules with a display format of 128 x 64 pixels. The package includes device drivers for GLCD modules based on the KS0107/KS0108 controller chipset or ST7920 chip. Also included is driver code for the SH1106 OLED display controller. 

Suitable GLCD and OLED modules are sold by Adafruit and Sparkfun. Compatible modules may be available at lower cost via eBay, AliExpress, etc.

NB: The package is not a hack of the Arduino "GLDC" library! My software was developed from scratch to be simpler, easier to read, more efficient and to optimise write speeds for text and bitmap image rendering. 

The drivers were designed for Microchip PIC devices, but hardware dependencies are confined to low-level driver files so as to make the code easily portable to other MCU device types, e.g. ATSAMD21.

Functions provided in the LCD Graphics library:

void LCD_Init(void); // LCD controller initialisation
void LCD_ClearScreen(void); // Clear LCD GDRAM and MCU RAM buffers
void LCD_Mode(uint8 mode); // Set pixel write mode (set, clear, invert)

void LCD_PosXY(uint16 x, uint16 y); // Set graphics cursor position to (x, y)
uint16 LCD_GetX(void); // Get cursor pos x-coord
uint16 LCD_GetY(void); // Get cursor pos y-coord

void LCD_BlockFill(uint16 w, uint16 h); // Fill area, w x h pixels, at cursor (x, y)
uint8 LCD_PutImage(uint8 *image, uint16 w, uint16 h); // Show bitmap image at (x, y)
uint16 *LCD_ScreenCapture(); // Return a pointer to the screen buffer

void LCD_SetFont(uint8 font_ID); // Set font for char or text display
void LCD_PutChar(uint8 uc); // Show ASCII char at (x, y)
void LCD_PutText(uint8 *str); // Show text string at (x, y)

// These macros draw solid rectangular objects at the current cursor position (x, y)
#define LCD_PutPixel() LCD_BlockFill(1, 1)
#define LCD_DrawBar(w, h) LCD_BlockFill(w, h)
#define LCD_DrawLineHoriz(len) LCD_BlockFill(len, 1)
#define LCD_DrawLineVert(len) LCD_BlockFill(1, len)

Character font sizes available: 8, 12, 16 and 24 pixels (char cell height, incl. descenders).
Some fonts are mono-spaced, others proportional; some fonts support bold weight.

The software package includes support for Microchip's "Graphics Resource Converter" (GRC) utility.
Bitmap image definitions generated by the GRC can be transformed into a bitmap format suitable for display using the library function LCD_PutImage().

The GitHub repository (link below) includes a test/demo application with all project files required for development using Microchip MPLAB.X IDE.

There is another package specifically for 1.3" OLED display applications using the Arduino IDE.

Go to GitHub repository for LCD/OLED Graphics Library

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This article is concerned with firmware design and implementation for microcontroller-based devices incorporating a "local" user interface (front panel) comprising an LCD screen and keypad (or a number of push-buttons). The technique can be extended to build a graphical user interface (GUI) comprising an LCD screen with touch-panel.

Typical applications will have many "screens" to be presented and, for each screen, a selection of user options for various actions, most of which will result in a switch to a different screen or a change in displayed information on the current screen. For all but the most trivial of applications, navigation from one screen to the next presents a challenge to the developer and can easily become a convoluted mess if not handled methodically...

Download article (pdf)

Digital Audio (PCM) Sound Effects Software

Appealing sound effects may be too complex to be generated in real time by a low-end micro-controller in an embedded device. However, sound effects may be synthesized by a purpose-built application and stored as a sequence of PCM samples in a data file. Saved sound effects can be loaded into flash memory in the target embedded system for fast access by an audio player function. The storage medium is typically a "serial data flash" (SDF) memory device interfaced to the MCU via SPI. However, the micro-controller’s internal flash program memory can also hold sound FX data.

PCM sound effects data files can also be produced from standard audio file formats such as WAV, MP3, etc, using "Audacity" - a free open-source audio editor application. There is a plethora of sound effects available for download on the internet. Audacity can also be used to record sounds using a microphone, CD player, sound synthesizer or musical instrument, etc. Once loaded into Audacity, audio data can be re-sampled at the required sample rate and then exported in “RAW” data format (stripped of header information) compatible with the target embedded player.

The software described in this article comprises a simple sound FX synthesizer application, an audio player function and various utilities to transfer sound FX data files between the SDF memory device and a removable mass-storage device, e.g. a USB flash drive. The software was originally developed for Microchip’s PIC32MX (32-bit) micro-controller family, but could be easily customized to suit others... more...

ATmega32U4 MCU Peripheral Function Library

... for use with Microchip/Atmel Studio IDE -- not Arduino!

Download Pro Micro AT_32U4 Function Library  (C source code files)

How to load program code into a Pro Micro module using Microchip/Atmel Studio IDE

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Disclaimer: Source code and other "intellectual property" offered as free downloads on this website are original works of M. J. Bauer, except where acknowledged to the contrary. Otherwise, any resemblance to prior art originated or developed by others is purely coincidental, or due to derivation from similar works or well-established art in the public domain. The author does not accept liability for any adverse consequence of the use of "intellectual property" obtained from this website or respective GitHub repository.