port by Thomas Friedrichsmeier

Note: Be sure to understand the info given at Mozzi on STM32-based boards - disambiguation . This page is about using Mozzi with the STM32 "libmaple based" core.; This port may look similar to, but uses a different default GPIO pinout than @hardware_stm32duino !

Status and peculiarities of this port

Compiles for and runs on a STM32F103C8T6 blue pill board, with a bunch of caveats (see below), i.e. on a board without a real DAC. Should probably run on any other board supported by Roger Clark's libmaple-based core (although this theory is untested).

Note: that at the time of this writing, Stev Strong's slightliy more recent fork of this core does not work with Mozzi, apparently due to a bug in pwmWrite().

If you want to use MIDI, be sure to replace "MIDI_CREATE_DEFAULT_INSTANCE()" with "MIDI_CREATE_INSTANCE(HardwareSerial, Serial1, MIDI)" (or Serial2)
MOZZI_AUDIO_INPUT_STANDARD is implemented in theory, but untested (feedback welcome)
getAudioInput() and mozziAnalogRead() return values in the STM32's full ADC resolution of 0-4095 rather than AVR's 0-1023.

twi_nonblock is not ported

Output modes

The following audio modes (see MOZZI_AUDIO_MODE) are currently supported on this hardware:

MOZZI_OUTPUT_EXTERNAL_TIMED
MOZZI_OUTPUT_EXTERNAL_CUSTOM
MOZZI_OUTPUT_PWM
MOZZI_OUTPUT_PWM_2PIN

The default mode is MOZZI_OUTPUT_PWM .

MOZZI_OUTPUT_PWM

Standard pulse width modulated output to one (mono) or two (stereo, see MOZZI_AUDIO_CHANNELS) GPIO pins. Default pinout: PB8 (mono/left), PB9 (right channel in stereo). This mode uses two hardware timers: One for the PWM (Timer 4 when using the default pin configuration), and a second for updating the output at audio rate. The default audio resolution is 10 bits, which results in a carrier frequency of ~70kHz on a 72MHz CPU. On slower boards you will have to descrease this. The following settings may be costumized, if desired:

#define MOZZI_AUDIO_PIN_1       ...  // Left / mono output pin. Default: PB8
#define MOZZI_AUDIO_PWM_TIMER   ...  // Must be set ot the hardware timer connected to the above pin. Default: 4
#define MOZZI_AUDIO_UPDATE_TIMER ... // Second hardware timer to claim. Default 2
#define MOZZI_AUDIO_BITS        ...  // Output resolution in bits. Default is 10
// For stereo, only:
#define MOZZI_AUDIO_PIN_2       ...  // Right channel output pin. This *must* be connected to the same hardware timer as MOZZI_AUDIO_PIN_1 ! Default: PB9

MOZZI_OUTPUT_2PIN_PWM

This mode is very similar to MOZZI_OUTPUT_PWM, but splitting output for a single channel across two GPIO pins for better resolution. For details on the required hardware setup, and configuration tradeoffs, see MOZZI_OUTPUT_2PIN_PWM . Stereo output is not available in this mode. Output is at 2*7 bits at up to 560kHz carrier frequency (but limited to 5 times audio rate).

Customizable configuration options:

#define MOZZI_AUDIO_PIN_1       ...  // High byte of the output. Default: PB8
#define MOZZI_AUDIO_PIN_2       ...  // Low byte of the output. Default: PB9
#define MOZZI_AUDIO_PWM_TIMER   ...  // Must be set to the number of the hardware timer connect to the above pins. Default: 4
#define MOZZI_AUDIO_UPDATE_TIMER ... // Second hardware timer to claim. Default TIM2
#define MOZZI_AUDIO_BITS_PER_CHANNEL  ...  // Bits per pin. Default is 7

MOZZI_OUTPUT_EXTERNAL_TIMED and MOZZI_OUTPUT_EXTERNAL_CUSTOM

See External audio output The (single) hardware timer claimed for MOZZI_OUTPUT_EXTERNAL_TIMED may be configured using "MOZZI_AUDIO_UPDATE_TIMER" (default: TIM2).