Thursday, December 05, 2019

Speak&SID - CPC MIDI IN SID + AY Synth

Published on Dec 4, 2019 Michael Wessel

"Turn your CPC into a powerful MIDI IN SID + AY Synthesizer!

A new mode has been added to the Speak&SID firmware - the MIDISID mode.

In this mode, Speak&SID can receive MIDI messages over its UART header to which a 10 $ MIDI breakout board is connected via Dupont cables. The Microkorg is used solely as a MIDI controller here (no sounds from the Microkorg). The incoming MIDI messages are then received by the CPC by reading the Speak&SID serial buffer byte by byte, and analyzed and translated into (polyphonous) notes for the internal CPC AY 3-8912 soundchip. At the same time, these notes are also sent to the (ARM)SID chip on the Speak&SID card, which is then also playing the received notes (currently only 1 voice - but for the AY we are using all 3 voices). With a little bit of additional work on the CPC machine code program, all of the SID's capabilities will be controlled via MIDI and/or the CPC keyboard keys in the near future, hence turning a CPC with Speak&SID into a powerful and inexpensive, versatile SID + AY 3-8912 MIDI IN realtime synthesizer. It is even possible to add one more soundgenerator to the mix - the SpeakJet chip is also a 4channel sound synthesizer! Interestingly, as you can hear, the SID and AY sound chip are slightly detuned from each other. Not sure why this is... maybe I need to tune the SID or AY frequencies a bit? Or maybe that's an ARMSID inaccurarcy? Have to try with my real 6581."

Speak&SID CPC - 2nd Demo, Line Out Recording + LEDs!

Published on Nov 9, 2019 Michael Wessel

"This time, a line out recording of Speak&SID CPC. Last video was taken from the camera's mic. Speak&SID's GPIO LEDs are controlled by the CPC, not the firmware. The 4 LEDs, from left to right, are the GATE bits of the corresponding SID cannels, and the 4th LED indicates changes in filter resonance. As the LEDs are controlled by the CPC / SID Player software, it is also possible to turn this LED display into a volume level indicator display, or other kinds of "lightshows". It is easy to patch the ASM for that (all the SID registers are modeled in software there).

In the meantime, the 2nd PCB revision boards arrived. So I should be able to ship out the first Speak&SID cards early December."

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