MATRIXSYNTH: Building a Drum Computer for the RetroChallenge 2021/11

Sunday, October 17, 2021

Building a Drum Computer for the RetroChallenge 2021/11


video upload by Michael Wessel

This one is in via Michael Wessel.

"This is my entry for the RetroChallenge 2021/10.

My Hackaday project page explains some more details"

And via Hackaday:

"In this episode, I extend the pattern-based drum computer to full 16 steps / beats (4 bars x 4 beats), and tailor for real time drum pattern input (like a real drum computer).

This requires inputting data from the keypad using the KIN (Keyboard Input) op-code, whilst playing back the pattern, and hence isn't possible with the standard Microtronic KIN. Thus, I implemented a non-blocking KIN behavior. Utilizing 2 more vacuous op-codes, I can now toggle between the standard blocking KIN input behavior, and the new non-blocking behavior.

The op-codes for determining the KIN mode of operation are 3F0 (blocking KIN mode) and 3F1 (non-blocking KIN mode). By default, the Microtronic only uses blocking KIN. The vacuous op-codes 3F0 and 3F1 are idempotent immediate AND (ANDI) op-codes, i.e., the operand 0xF = 0b1111 = 15 is idempotent for 4bit registers, and hence, no (existing or new) program would ever use them. So it is safe to assign the mode toggling extra side-effect to them.

In general, the following vacuous op-codes are available for side effect extension:

MOV x,x: copy register x onto register x, 0xx
ADDI 0,x: add 0 to register x, 50x
SUBI 0,x: subtract 0 from register x, 70x
ANDI F,x: bitwise AND of register x with F, 3Fx"

Full details on Hackaday.

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