Since the synthesizer state machine is effective in defining when a 'note' envelope is terminated, it is then possible to store all the subsequent 'notes' in a stream of consecutive frames. This allows 'staccato' and 'legato' music modes (see MML support below). release start (the state machine counter at which the Release phase starts).time scale (number of samples between a state change).Limiting the fade to 5 or 6 bits (-50/-60dB) is necessary to avoid drop of performance and higher sampling rates.ĭue to RAM limitation, every note only uses two dimensions for the ADSR envelope: Since the PIC12/PIC16 doesn't have hardware support for multiple bit-shift, shifting is a O(N) operation.

The approximation of a continuous fade, so evident and ugly in the linear scale, is actually not so bad once played through a speaker. Int8_t value = voice_wf_next(&(voice->wf)) Įvery bit shift is approximately -10dB of gain. Uint8_t gain = adsr_next(&(voice->adsr)) With this approximation, the gain can be seen as a number of bit shifts: Instead of allowing variable ADSR parameters, this fork implement a quasi-fixed envelope function, using only bit shift operators to avoid multiplications (that in a RISC MCU would kill the performances).Ī clever way to optimize this is to follow the natural logarithmic scale of the human hearing, and use exponential gain instead of linear ones. The ADSR is a cut-down version of the main sjlongland/atinysynth project.

Spoiler: yes, that's possible, even using the free version of the XC8 compiler.ġ:17 Korobeiniki (a.k.a Tetris A-type tune), 3 voices, 9.7kHz sampling rate, total size code+tune: 1771 code words, 72 RAM bytes, on a 8-pin PIC12F683 ADSR: principle of operation The goal is to implement a polyphonic tune player in only 2K instructions (containing the code and the tune data) and to stay in 128 bytes of RAM. This is a fork of the sjlongland/atinysynth project for AT AVR MCUs, but optimized for the tiniest PIC12xxx Microchip microcontroller. It features multi-channel direct synthesis with ADSR envelope, with a handy MML compiler. This project is intended to be a polyphonic sequencer for use inĮmbedded 8-bit micro-controllers. ADSR-based Polyphonic Sequencer for tiny PIC12/PIC16

Free c compiler for pic16