Chris Anderson @chrisanderson1973@librem.one

Saturday morning work, at the office.

A good night working through parts of the USB audio stack. I am now looking at the audio data transfers to USB, as.well as the ADC sampling (which is the easy part!). Fun stuff!

The “kitted” DSP platform is altogether now, such that it is. It’s not the cleanest-looking mock-up in the world, but it will get the job done. I believe I may hold off on working with it much until I arrive back later this week. It might be a good idea to clean up the lab area since I finally have a sensible hardware platform for prototyping.

Kitting partially there!

Today’s work is all about the power supply (9V battery to 5V regulator - for now). I also need to place the input amplifier and STM32 Micro system in a kit/container for transport.

The “new” amplified I prototyped probably isn’t required, and it is not quite right, in terms of design, due to the reliance on a double-ended power supply and amplifier configuration. The single supply amplifier design from the other week was tweaked to amplify at 10x, rather than only 2x, and the result is a maximum Vpp of 1V, which is the current target.

These oscilloscope pics show the original and then output signals, along with the iPhone playing the constant synth sound!

More work today - getting the input amplifier integrated and looking at the initial DSP chain.

Updated schedule.

Finished prototype of the input amplifier.

Finished the pre-amp prototype this morning. Ready for testing this evening and further integration.

We are now looking into the input amplifier and DSP input stage design. A gain amplifier is needed to give the signal enough amplification to fill out the 1V range used in the DSP engine. At present, the USB audio interface will handle 48 kHZ/16bits. For any higher range, and we are looking at 192kHz at 24bits, but that will require an external CODEC. Planning this prototype to get things going.

In parallel with the audio effects hardware, I am kicking around the synth project again.

Within the "module manager" app, device detection now works on Mac. It may end up being another ordeal with Linux, and Windows should be somewhat simply - although I have yet to compile the Qt application on Windows! Nice progress, overall.

More work tonight, integrating USB serial port connectivity with the "module manager" application, for lack of a better name. This will be a cross platform deal, usable on the Mac, Linux, Windows, or on the specially designed digital audio workstation (an embedded Linux platform).

Updated schedule for the audio DSP project: Making a lot of headway, and I am now working on a companion app for Mac, Linux, and Windows alongside the firmware. May will be busy!

More pics from the weekend!

Fun weekend near Boone in the NC mountains! #family #easter #peaceandquiet #boone #andersonfamily #fun #cabin #2022

Great progress with I2C using standard peripherals on STM32F407VG.✅

Tonight’s work was about refining the I2C hardware interface and building a project box to house the digital and embedded parts of the design…. Spot the analog input amplifier which will go into a project box next.👍

Some progress since January, getting a QT-based interface running on an iMX8 platform. Also, some work was done on input and buffer stages for the “effects loop” (the hardware version).