.. zephyr:board:: opentitan_earlgrey

Overview

The OpenTitan Earl Grey chip is a low-power secure microcontroller that is designed for several use cases requiring hardware security. The OpenTitan Github_ page contains HDL code, utilities, and documentation relevant to the chip.

Hardware

RV32IMCB RISC-V "Ibex" core
128kB main SRAM
Fixed-frequency and AON timers
32 x GPIO
4 x UART
3 x I2C
2 x SPI host
1 x SPI device
Various security peripherals

Detailed specification is on the OpenTitan Earl Grey Chip Datasheet_.

Supported Features

.. zephyr:board-supported-hw::

Programming and Debugging

.. zephyr:board-supported-runners::

First, build and install Verilator as described in the OpenTitan Verilator Setup_ guide .

Building and Flashing

Here is an example for building the :zephyr:code-sample:hello_world application. The following steps were tested on OpenTitan master branch @ 6a3c2e98.

.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: opentitan_earlgrey :goals: build

The OpenTitan Vchip_sim_tb tool can take the Zephyr .elf as input and place it in simulated flash. The OpenTitan test ROM will then run in simulation, read the manifest header from simulated flash, and begin executing Zephyr from the entry point.

.. code-block:: console

$OT_HOME/bazel-bin/hw/build.verilator_real/sim-verilator/Vchip_sim_tb --verbose-mem-load
-r $OT_HOME/bazel-out/k8-fastbuild-ST-2cc462681f62/bin/sw/device/lib/testing/test_rom/test_rom_sim_verilator.39.scr.vmem
--meminit=otp,$OT_HOME/bazel-out/k8-fastbuild/bin/hw/ip/otp_ctrl/data/img_rma.24.vmem
--meminit=flash,$ZEPHYR_PATH/build/zephyr/zephyr.elf

UART output:

.. code-block:: console

I00000 test_rom.c:135] Version: earlgrey_silver_release_v5-9599-g6a3c2e988, Build Date: 2023-01-17 16:02:09 I00001 test_rom.c:237] Test ROM complete, jumping to flash (addr: 20000384)! *** Booting Zephyr OS build zephyr-v3.2.0-3494-gf0729b494b98 *** Hello World! opentitan_earlgrey

References

.. target-notes::

.. _OpenTitan Earl Grey Chip Datasheet: https://opentitan.org/book/hw/top_earlgrey/doc/specification.html

.. _OpenTitan GitHub: https://github.com/lowRISC/opentitan

.. _OpenTitan Verilator Setup: https://opentitan.org/guides/getting_started/setup_verilator.html