Crate teensy4_bsp

A Rust board support package (BSP) for the Teensy 4.

teensy4-bsp supports the following boards:

• Teensy 4.0
• Teensy 4.1
• Teensy MicroMod

If you’re just getting started with embedded Rust development on the Teensy 4, take a look at the board module. This module provides pre-configured drivers and helper functions to define hardware drivers.

Peripherals are re-exported from the imxrt-hal hardware abstraction layer. For more information on drivers, consult the imxrt-hal documentation. Note that imxrt-hal drivers depend on low-level resources from imxrt-ral. For convenience, the BSP also exposes imxrt-ral. Combine imxrt-hal and imxrt-ral to have full control of your hardware.

Finally, the BSP provides a runtime to simplify application development. It exposes board pins through the pins module. And, it provides the imxrt-log API for advanced logging features.

Features

teensy4-bsp supports these features.

Flag	Description
"rt"	Adds runtime support using imxrt-rt.
"usb-logging"	Enables the LoggingFrontend convenience.

When "usb-logging" is enabled, the BSP defines the USB_OTG1 interrupt handler. This may conflict with your own USB_OTG1 handler, resulting in a duplicate definition. If you want to define your own USB_OTG1 handler to perform USB logging, do not enable "usb-logging".

Runtime

When the runtime is enabled, teensy4-bsp defines the memory map. In order to use the memory map, you must link your program with t4link.x.

The memory organization includes

• 320 KiB of DTCM, comprised of
  • a 16 KiB stack.
  • the vector table.
  • all zero- and runtime-initialized data (.bss, .data).
• 192 KiB of ITCM, containing all instructions (.text).
• 512 KiB of OCRAM, comprised of
  • any uninitialized data (.uninit)
  • a 16 KiB heap.

If the runtime is disabled, then teensy4-bsp does no define the memory map, and it does not depend on imxrt-rt. Consider disabling the BSP’s runtime feature if you want to implement your own runtime, or if you want to use imxrt-rt to define your own memory map.

Environment variable overrides

You can override the size of some memory regions by setting environment variables.

• To change the stack size, set TEENSY4_STACK_SIZE when building.
• To change the heap size, set TEENSY4_HEAP_SIZE when building.

The examples below show how to set a 4096 byte stack using its environment variable.

TEENSY4_STACK_SIZE=4096
TEENSY4_STACK_SIZE=4k     # Convenience for multiples of 1024 bytes.
TEENSY4_STACK_SIZE=4K     # Equivalent to the above.

Notes

SRTC reset by loader

When the SRTC is enabled, setting the board into program mode then using the Teensy Loader application (GUI) to reboot it will set the current time (Unix epoch, but time in local timezone). This will overwrite whatever time you may have previously set and is ambiguous around the backwards daylight savings transition point.

Re-exports

• pub use imxrt_hal as hal;
• pub use imxrt_log as logging;
• pub use imxrt_ral as ral;
• pub use imxrt_rt as rt;
  rt
• pub use teensy4_pins as pins;

Modules

• board
  Pre-configured board resources.

Enums

• LoggingFrontendrt and usb-logging
  The logging frontend.

Constants

• EXT_SYSTICK_HZ
  SYSTICK external clock frequency.