README.md

Tock Capsules

Capsules are drivers that live in the kernel and are written in Rust. They are required to conform to Rust's type system (i.e. no unsafe). Capsules are platform agnostic and provide a range of features:

• Drivers for sensors or other ICs
• Virtualization of hardware resources
• Syscall interfaces for userland applications

When using hardware resources, capsules must only use features provided by the HIL (hardware interface layer). This ensures they can be used on multiple microcontrollers and hardware platforms.

Capsules have some flexibility in how they present access to a sensor or virtualized hardware resource. Some capsules directly implement the Driver trait and can be used by userland applications. Others provide an internal interface that can be used by other in-kernel capsules as well as a Driver interface for applications.

List of Tock Capsules

The list of Tock capsules and a brief description.

Sensor and other IC Drivers

These implement a driver to setup and read various physical sensors.

• FXOS8700CQ: Accelerometer and magnetometer.
• ISL29035: Light sensor.
• LPS25HB: Pressure sensor.
• SI7021: Temperature and humidity sensor.
• TMP006: Infrared temperature sensor.
• TSL2561: Light sensor.

These drivers provide support for various ICs.

• FM25CL: FRAM chip.
• LTC294X: LTC294X series of coulomb counters.
• MAX17205: Battery fuel gauge.
• MCP23008: I2C GPIO extender.
• MX25r6435F: SPI flash chip.
• PCA9544A: Multiple port I2C selector.
• SD Card: Support for SD cards.

Wireless

Support for wireless radios.

• nRF51822 Serialization: Kernel support for using the nRF51 serialization library.
• RF233: Driver for RF233 radio.
• BLE Advertising: Driver for sending BLE advertisements.

Libraries

Protocol stacks and other libraries.

• IEEE 802.15.4: 802.15.4 networking.
• USB: USB 2.0.
• Segger RTT: Segger RTT support. Provides hil::uart interface.

MCU Peripherals for Userspace

These capsules provide a Driver interface for common MCU peripherals.

• ADC: Individual and continuous samples.
• Alarm: Oneshot and periodic timers.
• CRC: CRC calculation.
• DAC: Digital to analog conversion.
• GPIO: GPIO configuring and control.
• I2C: I2C master and slave access.
• RNG: Random number generation.
• SPI: SPI master and slave.

Helpful Userspace Capsules

These provide common and better abstractions for userspace.

• Ambient Light: Query light sensors.
• App Flash: Allow applications to write their own flash.
• Button: Detect button presses.
• Console: UART console support.
• Humidity: Query humidity sensors.
• LED: Turn on and off LEDs.
• Temperature: Query temperature sensors.

Virtualized Sensor Capsules for Userspace

These provide virtualized (i.e. multiple applications can use them simultaneously) support for generic sensor interfaces.

• Asynchronous GPIO: GPIO pins accessed by split-phase calls.
• 9DOF: 9DOF sensors (acceleration, magnetometer, gyroscope).
• Nonvolatile Storage: Persistent storage for userspace.

Virtualized Hardware Resources

These allow for multiple users of shared hardware resources in the kernel.

• Virtual Alarm: Shared alarm resource.
• Virtual Flash: Shared flash resource.
• Virtual I2C: Shared I2C and fixed addresses.
• Virtual SPI: Shared SPI and fixed chip select pins.
• Virtual UART: Shared UART bus.

Utility Capsules

Other capsules that implement reusable logic.

• Nonvolatile to Pages: Map arbitrary reads and writes to flash pages.
• AES Encryption: AES-CCM encryption.