Chris Anderson @chrisanderson1973@librem.one

A quick update: The ALSA audio project for Linux has a utility called alsaloop, which provides an audio loop back through “capture” and “playback” interfaces. On the Toradex Apalis iMX8 platform, using alsaloop, I was able to play an instrument in a loopback configuration with an analog “line in” and a headphone jack. This is a huge deal, because it allows for an analog-in to digital to analog out path, and a great embedded device for building a complex effects processor!👍 More work to follow!

More work with the iMX8 platform to try and mold it into an audio effects and/or digital audio workstation. Some quick tests recently have shown that USB audio is a little slow on the iMX8, in that the set up has a noticeable delay and that the USB interface doesn’t quite keep up. That is, at least with the port audio stack. So, the other option is to run analog in/out on the board, and have it work more like a deluxe effects box. The analog in sounds great. An analog out test is next.

Still working on Linux audio on the Toradex iMX8 platform.....

Today, I made a first stab at a recording app for the coming iMX8-based DAW system. The audio recording/playback set up is the very fist step. Today, I was able to record some improv off my Ibanez!

Nice bit of audio work and embedded Linux work tonight. I managed to have the Linux sound framework working, taken from a Yocto build. It was enough to instantiate the audio card interfaces, including USB audio, and even run audio playback through HDMI and a DUET USB audio interface.

More work on my power amplifier design tonight. I added an auxiliary output that is available after any gain/distortion and reverb, and before the output (power) stage.

Looking into new DSP platforms, rather than the very minimal STM32F series I researche di nthe fall.... Starting with the Cyclone V FPGA platform, using the Quartus Prime Lite Edition.

I've gotten as far as designing the printed circuit board, including the power supplies and power amplifier stage!

A starting design for a 100W guitar amplifier, complete with distortion and reverb. I need to add an auxiliary out circuit, as well. Looking good!

Turns out, I like building stuff. 100W amplifier coming right up.

Some EE work this morning and in the last few days. Looking into building a guitar amplifier!

A favorite software technique I use: dynamically loading libraries and using function pointers to access the loaded library. Works in just about any contact in C/C++ and I have used it to make projects simpler to manage, and faster to compile. It's also very useful for building plugins.

More work tonight on the embedded Linux platform. I am building my custom Qt app and Audacity, together, on a Weston (Wayland) reference compositor. The goal is to bring up Audacity on the board and work with the audio interfaces.

Continuing work on a Linux-based effects system....I had to move up from anything STM32-based. There is simply too much efficiency in using Linux.

It's been a while, but I simply had no "spark" as far as writing new/interesting software is concerned, for the last little while.

This is related to a work project, but I am well on my to creating a Qt/Golang-based Modbus simulation program. I have managed to bind Qt/Quick/Qml to Go, and this is all enough to run a full-blown simulation. More to come.

I am switching directions, but I am getting into what all I'd really like to do anyway, and that's solve a problem I have always seen with audio production setups. So, the new goal is to mostly skip over reinventing the wheel (USB audio) and delve into digital audio workstation development using embedded Linux and various control. Lots more to come.

This kind of took most of Sunday, but whatever.... I built Audacity for the Yocto embedded Linux. I have a graphical environment already, so it will be handy to have access to Audacity to get a summary of the audio capabilities on the Apalis iMX8 platform. Plus a little fun running Spotify in Fedora.

Audacity - I am building this on the iMX8 system to test out the basic audio interfaces that are provided between the iMX8 Apalis SOM and Ixora carrier board.

Living the dream! I have some hardware work to do on the STM32 (ie. making a whole design on a printed circuit board) before I can do much more with that system. A limiting factor, as well, is the latency minimization on the USB audio interface. It's still manageable to use for a certain number of effects, but I need to make sure that I can do enough audio processing to have a viable product. The backup is Linux, and I will pursue that in the coming weeks, as well.