DSP Firmware

freetribe/dsp/src/*

The DSP kernel receives commands from the CPU and processes audio frames. A user defined module runs in the audio callback, with an interface similar to many plugin formats. The code here is less developed, but will gradually be made more similar to the CPU firmware.

Kernel

freetribe/dsp/src/kernel/knl_*

The kernel orchestrates a set of services, built on device and peripheral drivers. The rest of this section looks at each layer, from the hardware up.

Peripheral

freetribe/dsp/src/kernel/peripheral/per_*

The peripheral layer accesses hardware registers directly to initialise and control DSP peripherals, such as SPI or SPORT (for i2s). Currently, Interrupt Service Routines push directly to queues in the peripheral driver. Queues should be moved up to a device layer, with ISRs executing optional callback functions. Peripheral drivers should be self-contained and deal with a single peripheral and its associated DMA channels.

Device

freetribe/dsp/src/kernel/device/dev_*

The device layer does not currently exist. This is where we should handle peripheral interrupts, pushing data to queues and providing access for the service layer above.

Service

freetribe/dsp/src/kernel/service/svc_*

The service layer uses drivers to provide services to the kernel. For example, the CPU command service parses and handles messages received from the CPU via SPI. Services are implemented as non-blocking state machines and should do as little as possible each time they are invoked.

Module

freetribe/dsp/src/modules/*

Modules are whatever we make them. We override functions to provide initialisation, audio processing, and parameter change handling. The module_process() function is called for each audio sample, block processing is not yet supported. The module_set_param() function is called by the CPU command service when the appropriate message is received.

What's currently called 'module' will be refactored into an 'app', similar to the CPU firmware. An app could host a set of modules, providing a patchable virtual modular system.

See the Freetribe Tutorial for more.