Saturday, May 29, 2021

Bluetooth Stereo Audio Receiver JDY-62 module and the Bluetooth 4.0 CSR dongle transmitter

JDY-62 is an affordable Bluetooth stereo audio receiver module with great sound qualities for the price provided the ground connection is properly made. To send audio from PC to the JDY-62 module I have used the Bluetooth 4.0 CSR dongle transmitter that works well on Windows 10 and acts like a sound card.

Bluetooth Stereo Audio Receiver JDY-62 module and the Bluetooth 4.0 CSR dongle transmitter

JDY-62 module pinout

JDY-62 module pinout

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.