ALFONSo stands for :

Analog Low Frequency Oscillator Nolinear Sequencer

In this implementation MK-ICL8038.

• Meta
• Basics
• Power Supply
• ICs used in VCO & Mixer
• Frequency Counter
• Early implementation
• Development pictures
• Current wiring diagram
• Upcoming implementations

Scope:

• The project from my passion of analog synthesizers and the love of the patterns, rhythms and mats that colored the majority of the 70s and 80s classics. In particular the analog sequencers and LFOs.
• The use of analog IC monolith signal generators operated in BF in the 1Hz band up to 25KHz. Can be used as VCO/LFO. This first research intentionally uses the older, now obsolete, but well known Intersil ICL8038.
• The digital control interface via USB is based on an old and well-known Microchip 18-series microcontroller. The PIC18F4550 is a widely used mC and there is a large amount of example code and tutorials available on the web. However, I personally always suggest having its datasheet handy and dedicating the time to understand its correct functioning.
• Alfonso uses the USB 2.0 peripheral contained in the 18F4550 microcontroller. The firmware exposes the USB port as a CDC (USB communications device class). This allows it to be recognized by all OSes as an RS232 serial port. I originally intended to use the USB port as a Human Interface Device (HID) but due to its limitations I decided to implement it as a CDC and build a proprietary protocol on it.

This first implementation is oriented to develop and test all the HW functionalities of the VCOs/LFOs and the core SW libraries for their command. For this, a first mixer with the basic functions was developed.

Both the control logic section and the analog section with the VCO and the mixers are still being prototyped via breadboard. Once the functionality is stabilized, I will create a welded version for better signal quality. Obviously the air links are not optimal.

• It is my intention, once the project based on the Intersil ICL8038 is completed and stabilized, to re-adapt it for use with the EXAR XR-2206 Monolithic Function Generator. IC is more modern and seems to compensate for certain problems of the ICL8038. It is also still supported and in production.
• The impact on the Firmware of the transition of the current mC PIC18F4450 towards the new version, currently supported by the MCC of MPLABX, mC PIC18F45K50 is minimal. So as soon as the current version stabilizes, I'll switch to this mC.