Monday, May 10, 2021

Pinning files on LibreOffice taskbar and other apps in Windows 10 - an alternative to recent files

I was searching a way to show the recent files in LibreOffice by right clicking on the pinned app on the taskbar but it appears it can't be done in Windows 10. But, there is a better way - pinning the most used documents.

Pinning files on LibreOffice taskbar in Windows 10

To pin your favorite files on LibreOffice (or any other apps like folders in Explorer) first pin the application on the Windows taskbar by dragging the icon from the desktop to the taskbar.

Pinning files on LibreOffice taskbar in Windows 10 - 1
Click to enlarge

Then to pin a file, drag the file from Windows explorer to the desired app on the taskbar.

Pinning files on LibreOffice taskbar in Windows 10 - 2

From now on you can just right click on the taskbar app and select which file do you want to open.

Wednesday, April 21, 2021

Building a Digital Clock with RGB Lamp & Spherical Shelf DIY

Here is how to build a simple digital wall clock encased in a spherical shelf that could make a nice gift for someone.

The clock is based on an ATmega328PB microcontroller that is using a 32.768 kHz crystal for time keeping. It also has 6 RGB leds that act as a night lamp or simply for aesthetic purposes.

Digital Clock With RGB Lamp & Spherical Shelf DIY

Thursday, February 25, 2021

Playing music and tones using a piezo buzzer - library for AVR microcontrollers using timer interrupt | ATmega328P, ATmega88

This is a library for playing chiptunes music using PWM and a piezo buzzer. Tones with different frequencies and timeouts can also be produced. The library uses a timer interrupt so the functions are non-blocking meaning that while a song or tone is generated the CPU can do other things. Timer 1 is used for PWM and another 8 bit selectable timer (0 or 2) is used to trigger the interrupt every 1ms. When a note ends the code inside the interrupt will calculate the PWM frequency of timer 1 based on the next note.

Optionally a led can be made to blink with the music rhythm.

The piezo buzzer must be connected to pins OCR1A and OCR1B which are set to have opposite polarity - when one pin is high the other one is low, then the polarity is reversed. This way you can make the buzzer louder with a lower voltage because the buzzer will see 10V even if the microcontroller outputs 5V.

Playing music and tones using a piezo buzzer - library for AVR microcontrollers using timer interrupt | ATmega328P, ATmega88

Types of buzzers

Before going any further I should clarify regarding the types of buzzers for those who are not familiar with them.

There are passive buzzers and active buzzers.

Saturday, February 6, 2021

Colorspace conversion between RGB and HSL library code for AVR microcontrollers | ATmega328P

I had a project where I needed to crossfade RGB colors and I thought why not using the HSL color space instead of the RGB color space because with the HSL the code looks neater and the Hue (color), Saturation and Lightness can easily be modified to create all kinds of light effects.

Colorspace conversion between RGB and HSL library code for AVR microcontrollers | ATmega328P

Converting HSL to RGB

HSLtoRGB(hue, saturation, lightness, rgb[])

Thursday, February 4, 2021

How to control RGB leds | RGB fader library for AVR ATmega328P

RGB leds are fun and because they can be used in many projects I have decided to make a library to easily crossfade the colors of one or multiple RGB leds.

To see this library used in a real project, check out this video Digital Clock With RGB Night Lamp & Spherical Shelf.

How to control RGB leds | Crossfading RGB leds | Library for AVR ATmega328P

Crossfading an RGB led in the RGB colorspace

Wednesday, February 3, 2021

Multi-channel software PWM library for AVR microcontrollers | ATmega328P

What you do when you run out of PWM pins on hardware? You make software PWM of course. This library is based on "AVR136: Low-Jitter Multi-Channel Software PWM" application note. It supports up to 10 PWM channels (more can be added) and it's suitable for led dimming, DC motor control and RGB led controller.

Multi-channel software PWM library for AVR microcontrollers | ATmega328P

Since this method is already explained in the AVR136 app note I won't go in to too many details. So the basic principles behind software PWM are this. A timer interrupt is set to trigger every 256 system clocks. For 8 bit timers the interrupt is on overflow and for 16 bit timers is on compare match. A 16 bit timer has the advantage that the base frequency can be modified. On every interrupt a variable "softcount" is incremented from 0 to 255 and each time is compared against each PWM channel. At the beginning of the cycle the pins are set high and when "softcount" equals to a channel's set value then the specific pin is set low. On 8MHz CPU the ISR takes between 4 and 10us to execute the code depending on how many channels and on how many ports there are. The size of the "softcount" variable dictates the PWM resolution and it is set to 8 bits. 

Saturday, January 23, 2021

Binary Code Modulation (BCM) aka Bit Angle Modulation (BAM) library for fading leds | ATmega328P

Binary Code Modulation (BCM) it's an amazing method for led dimming and was invented by Artistic Licence. It's like PWM but not really. The main advantage over PWM is the low CPU usage regardless of how many leds it controls.

This library provides a fast implementation of Binary Code Modulation useful for controlling RGB leds and dimming multiple leds for creating animations like led cubes and includes an array for logarithmic brightness. A complete cycle takes 8 timer interrupts and each interrupt takes only 4us on a 8MHz CPU. The leds can be on different ports.

Bit Code Modulation (BCM) aka Bit Angle Modulation (BAM) library for RGB led dimming - 8-bit

How Binary Code Modulation (BCM) works and how it differs from PWM

To dim a led with PMW is simple. If you want the led to be half as bright you turn the led on for 50% of the cycle and 50% for the other half. Or 20% on and 80% off for an even dimmer led.


PWM example

Bit Angle Modulation uses the weight of each bit in a binary number. For example in one byte there are 8 bits with numbers from 0 to 7. Bit 0 is called the Least Significant Bit (LSB) and it's weight is 1. Next bit 1 has a weight of 2, bit 2 has a weight of 4, then 8, 16, 32, 64 and 128. Bit 7 is called the Most Significant Bit (MSB) because it has the highest weight - 128.

8-bit binary weight

Monday, January 18, 2021

7 segment display library for AVR microcontrollers | ATmega328P

There are many ways to control a seven segment display - using a dedicated IC or shift registers which are preferred because they don't require many pins. However this library is made for when you have the segments driven directly from microcontroller pins and each digit is controlled using a transistor.

You have the option of padding the numbers with zeros and displaying them at a certain position, useful for making digital clocks.

To see this library used in a real project, check out this video Digital Clock With RGB Night Lamp & Spherical Shelf.

Seven segment display library for AVR microcontrollers

What is a 7-segment display

As the name suggests it is a display that is made up of 7 segments. Each segment is simply an LED. Including the dot there are actually 8 LEDs and this fits perfectly on an 8-bit microcontroller's port. This display is mainly made for numerical values but some alphabetical characters can be displayed as well.

Types of 7 segment displays

There are two types of seven segment displays - common cathode and common anode. Common cathode displays have all the ground sides (cathodes) of the LEDs connected together while common anode displays have all the positive sides (anodes) of LEDs tied together.

The 7 segment display can have from 1 up to 6 or 8 digits. One digit can display numbers from 0 to 9 and a dot for numbers with decimals. On 4 digit seven segment display the maximum number that can be displayed is 9999.

7 segment display internal equivalent circuit OPD-Q5621LE-BW
Figure 1: Internal equivalent circuit of a 7 segment display from OPD-Q5621LE-BW datasheet


Saturday, January 16, 2021

Read and debounce multiple buttons using interrupt | AVR microcontrollers

This library provides an easy way for reading and debouncing one or many buttons connected to a microcontroller. It can also read a button combination, button long press and button double press. Reading and debouncing takes only 50us every 10ms.

To see this library used in a real project, check out this video Digital Clock With RGB Night Lamp & Spherical Shelf.

Button debouncing library for AVR microcontrollers

What is button debouncing anyway?

Saturday, January 9, 2021

millis and micros library for AVR microcontrollers (ATmega328P) - milliseconds and microseconds time tracking

Having precise timing in microcontrollers is important in many projects. For this you can use the two libraries presented in this article - millis & micros.

millis library triggers a timer interrupt every 1 millisecond and increments the milliseconds variable. The user can select the size of the milliseconds variable ranging from char (8 bits) to long long (64 bits) with and overflow from 255 milliseconds to 584.9 million years.

micros library is almost the same as for millis except that the interrupt triggers every 100 microseconds and the variable microseconds is incremented with 100 microseconds. The overflow is between 255 microseconds and 584942 years. Triggering the overflow faster than 1 / 100uS will make the CPU slow especially on slower CPUs.

For both libraries the user can select which timer to use: Timer0, Timer1 or Timer2.

In the case of millis library it is recommended that all the active ISR must take less than 1 millisecond to complete otherwise the millis ISR would be delayed. For the micros the ISRs must finish in less than 100 microseconds. The faster the CPU clock the better.

For the milliseconds and microseconds variable decide if you really need a 32 or 64 variable (long and long long) because the bigger the variable the longer it takes to increment it. For example on a 1MHz CPU it takes about 77 microseconds to increment a long long variable. A clock can be made even with a char because it doesn't matter if it overflows since the time will be kept in minutes and hours vars. 

millis & micros library for AVR microcontrollers


Thursday, January 7, 2021

ISP programming rig for microcontrollers

I had to program many types of microcontrollers over the years and so I was thinking why not build a simple programming rig to make things easier. This rig is for the In-system programming (ISP) method and not for the UART method.

How to easily upload the code to any microcontrollers using ISP rig

The board in the above image is not the programming rig but a digital clock shown as an example. Notice the 6 pin header near the cap. The pins are not soldered through hole but on SMD pads. This way it can be easily de-soldered after finishing the project and on some space constrained projects this is a must.