SkajNätt

This is a message to inform that I've put this project on hold. I might continue at some time in the future, who knows? BUT: the things I learnt on this project are heavily influencing my latest project: https://hackaday.io/project/171471-pz1-6502-laptop

I've been busy trying out, reading about and understanding different aspects of using PWM as a means of getting audio out. There are some hidden treasures and possibilities, as well as pitfalls, that I really hadn't thought about before.

Having tried different solutions, I've now settled for a simplistic approach of using stereo 8-bit phase correct PWM. It sounds good enough without lots of complexity. Now onwards with the serial comms to send data to the soundchip.

This is the development board I'm using for the soundchip coding and testing.
I just added PWM- and noise-channels.
Running the Atmega328 at 16MHz@3.3V, which is slightly under-volted seems to work well. The MicroPython-board uses 3.3V, and I really would rather skip the voltage conversion if I can.
2 "speakers" because the sound is full stereo :D

I've started coding the sound expansion now. Working quite well. 4 channels stereo sound of 4 different types: sine, square, saw and triangle.
Next up is some communication with SkajNätt, and then PWM-channels, noise and adsr.

I have been away from this project for some time now. Had some fun coding a ZX81 demo :D

My immediate plan for SkajNätt is to make a sound-expansion card using an AVR as a DDS (Direct Digital Synthesis) chip with stereo output. 8 channels of simple waveforms and noise, ADSR, volume and pan per channel. Hopefully an analogue filter bank as well. Perhaps some rudimentary player built into the chip.

I've coded such things before, but not for the AVR. It'll be interesting to see how many of my goals I can reach with this.

Verified I2C and SPI functions of the MCP23S17 expansion card, everything works OK.

Built an expansion card for the MCP23S17. Time to test the connections now, before connecting chips.

I finally put up all the information I had on hackaday projects. More to come.

Soldered a proper connector for the LCD. Changed to PortB on the SPI-GPIO chip as the pinout was a much better fit for the LCD. Cleaned up the code quite a bit but still lacking string-output.

Connected a 40x3 alphanumeric LCD to the SPI-GPIO, wrote the first hard-coded setup and text to it.