Arduino++
When researching material for the SN76489 sound generator (documented in these previous articles) I discovered that many early microcomputer systems incorporated both the SN76489 and a YM2413 FM synthesizer. The Yamaha synthesizer looked like an interesting piece of hardware to explore. Here’s the result.
Ring Tone Text Transfer Language (RTTTL) was developed by Nokia in the 1980’s as a format and mechanism to manage ringtones on cell phones. As Nokia was leader brand at the time, this method was quickly adopted by many other manufacturers and became the de-facto standard for ringtones.
As cell phone hardware became more capable, the use of RTTTL has diminished in favour of more advanced sound production – today most ringtones are simply ordinary sound files. RTTTL files, however, are still useful in may applications.
Digitally addressable LEDs allow you to control large numbers of LEDs using digital communication to integrated control chips that manage all the rest for you. Matrices of these LEDs can make attractive displays but it can be somewhat of a pain to create bitmaps for display.
I use an Excel worksheet to marshal the data, needing me to just fill in numbers in a worksheet matrix.
In the first part and second part we examined the basics of the SN76489 hardware and the development of a library to manage sound production from this IC.
So, after all this effort, what kind of sound does this hardware produce? In this final post I run a few tests and dig into the resulting waveforms.
In the first part we examined the basics of the SN76489 hardware and how to manage it at the hardware interface between MCU and IC.
To enable sound generation experiments, the first thing I did was create a library to allow me to write sketches without worrying too much about this underlying hardware management.
Most computer games from the 80’s are recognizable by the bleeps and bloops they produced for sound. The easiest way to do this to toggle a single I/O pin to generate a square wave but there are some retro sound ICs that allow us to do much better for a minimal investment.
The SN76489 is one such IC that is still available at a very modest price and is easily interfaced to modern microprocessors.
Beginners love Arduino coding because there is so much of it available to just copy, load and go without too much thinking required.
Then they find that one thing they want to do is in one sketch and another in a second sketch. All they need to do is combine these sketches! This can be a big hurdle the first time it happens and many fail to get a satisfactorily working product.
There is a systematic approach to this that helps to ensure that things work.
When an application starts, any data was was part of a previous execution is reset to the initialised values of the variables. Often, however, it is desirable to maintain configuration and state values between processor resets. EEPROM is a good option to store these values.
This article explores ways to make this task easy.
The proper operation of a multiplexed displays relies on a feature of human visual perception known as flicker fusion – if a light is flashed quickly enough, individual flashes become imperceptible and the illusion of a steady light is created.
But how slow can you go before you can detect that flicker?
Part 1 and part 2 covered Standard MIDI Files and playing music at the right tempo. Once we have a MIDI stream, we need hardware that can play the notes.
In this part we’ll look at how to finally make a sound and how the MD_MIDIFile library supports this in software.
Arduino++ 