================== Espressif ESP32-C6 ================== The ESP32-C6 is an ultra-low-power and highly integrated SoC with a RISC-V core and supports 2.4 GHz Wi-Fi 6, Bluetooth 5 (LE) and the 802.15.4 protocol. * Address Space - 800 KB of internal memory address space accessed from the instruction bus - 560 KB of internal memory address space accessed from the data bus - 1016 KB of peripheral address space - 8 MB of external memory virtual address space accessed from the instruction bus - 8 MB of external memory virtual address space accessed from the data bus - 480 KB of internal DMA address space * Internal Memory - 320 KB ROM - 512 KB SRAM (16 KB can be configured as Cache) - 16 KB of SRAM in RTC * External Memory - Up to 16 MB of external flash * Peripherals - 35 peripherals * GDMA - 7 modules are capable of DMA operations. ESP32-C6 Toolchain ================== A generic RISC-V toolchain can be used to build ESP32-C6 projects. It's recommended to use the same toolchain used by NuttX CI. Please refer to the Docker `container `_ and check for the current compiler version being used. For instance: .. code-block:: ############################################################################### # Build image for tool required by RISCV builds ############################################################################### FROM nuttx-toolchain-base AS nuttx-toolchain-riscv # Download the latest RISCV GCC toolchain prebuilt by xPack RUN mkdir riscv-none-elf-gcc && \ curl -s -L "https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases/download/v13.2.0-2/xpack-riscv-none-elf-gcc-13.2.0-2-linux-x64.tar.gz" \ | tar -C riscv-none-elf-gcc --strip-components 1 -xz It uses the xPack's prebuilt toolchain based on GCC 13.2.0-2. Installing ---------- First, create a directory to hold the toolchain: .. code-block:: console $ mkdir -p /path/to/your/toolchain/riscv-none-elf-gcc Download and extract toolchain: .. code-block:: console $ curl -s -L "https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases/download/v13.2.0-2/xpack-riscv-none-elf-gcc-13.2.0-2-linux-x64.tar.gz" \ | tar -C /path/to/your/toolchain/riscv-none-elf-gcc --strip-components 1 -xz Add the toolchain to your `PATH`: .. code-block:: console $ echo "export PATH=/path/to/your/toolchain/riscv-none-elf-gcc/bin:$PATH" >> ~/.bashrc You can edit your shell's rc files if you don't use bash. Building and flashing NuttX =========================== Installing esptool ------------------ First, make sure that ``esptool.py`` is installed and up-to-date. This tool is used to convert the ELF to a compatible ESP32-C6 image and to flash the image into the board. It can be installed with: ``pip install esptool>=4.8.1``. .. warning:: Installing ``esptool.py`` may required a Python virtual environment on newer systems. This will be the case if the ``pip install`` command throws an error such as: ``error: externally-managed-environment``. If you are not familiar with virtual environments, refer to `Managing esptool on virtual environment`_ for instructions on how to install ``esptool.py``. Bootloader and partitions ------------------------- NuttX can boot the ESP32-C6 directly using the so-called "Simple Boot". An externally-built 2nd stage bootloader is not required in this case as all functions required to boot the device are built within NuttX. Simple boot does not require any specific configuration (it is selectable by default if no other 2nd stage bootloader is used). For compatibility among other SoCs and future options of 2nd stage bootloaders, the commands ``make bootloader`` and the ``ESPTOOL_BINDIR`` option (for the ``make flash``) are kept (and ignored if Simple Boot is used). If features like `Flash Encryption`_ are required, an externally-built 2nd stage bootloader is needed. The MCUBoot bootloader is built using the ``make bootloader`` command. This command generates the firmware in the ``nuttx`` folder. The ``ESPTOOL_BINDIR`` is used in the ``make flash`` command to specify the path to the bootloader. For compatibility among other SoCs and future options of 2nd stage bootloaders, the commands ``make bootloader`` and the ``ESPTOOL_BINDIR`` option (for the ``make flash``) can be used even if no externally-built 2nd stage bootloader is being built (they will be ignored if Simple Boot is used, for instance):: $ make bootloader .. note:: It is recommended that if this is the first time you are using the board with NuttX to perform a complete SPI FLASH erase. .. code-block:: console $ esptool.py erase_flash Building and Flashing --------------------- This is a two-step process where the first step converts the ELF file into an ESP32-C6 compatible binary and the second step flashes it to the board. These steps are included in the build system and it is possible to build and flash the NuttX firmware simply by running:: $ make flash ESPTOOL_PORT= ESPTOOL_BINDIR=./ where: * ``ESPTOOL_PORT`` is typically ``/dev/ttyUSB0`` or similar. * ``ESPTOOL_BINDIR=./`` is the path of the externally-built 2nd stage bootloader and the partition table (if applicable): when built using the ``make bootloader``, these files are placed into ``nuttx`` folder. * ``ESPTOOL_BAUD`` is able to change the flash baud rate if desired. Flashing NSH Example -------------------- This example shows how to build and flash the ``nsh`` defconfig for the ESP32-C6-DevKitC-1 board:: $ cd nuttx $ make distclean $ ./tools/configure.sh esp32c6-devkitc:nsh $ make -j$(nproc) When the build is complete, the firmware can be flashed to the board using the command:: $ make -j$(nproc) flash ESPTOOL_PORT= ESPTOOL_BINDIR=./ where ```` is the serial port where the board is connected:: $ make flash ESPTOOL_PORT=/dev/ttyUSB0 ESPTOOL_BINDIR=./ CP: nuttx.hex MKIMAGE: NuttX binary esptool.py -c esp32c6 elf2image --ram-only-header -fs 4MB -fm dio -ff 80m -o nuttx.bin nuttx esptool.py v4.8.1 Creating esp32c6 image... Image has only RAM segments visible. ROM segments are hidden and SHA256 digest is not appended. Merged 1 ELF section Successfully created esp32c6 image. Generated: nuttx.bin esptool.py -c esp32c6 -p /dev/ttyUSB0 -b 921600 write_flash -fs 4MB -fm dio -ff 80m 0x0000 nuttx.bin esptool.py v4.8.1 Serial port /dev/ttyUSB0 Connecting.... Chip is ESP32-C6 (QFN40) (revision v0.0) [...] Flash will be erased from 0x00000000 to 0x0003cfff... Compressed 248628 bytes to 106757... Wrote 248628 bytes (106757 compressed) at 0x00000000 in 2.5 seconds (effective 805.6 kbit/s)... Hash of data verified. Leaving... Hard resetting via RTS pin... Now opening the serial port with a terminal emulator should show the NuttX console:: $ picocom -b 115200 /dev/ttyUSB0 NuttShell (NSH) NuttX-12.8.0 nsh> uname -a NuttX 12.8.0 759d37b97c-dirty Mar 5 2025 19:42:41 risc-v esp32c6-devkitc .. _esp32c6_debug: Debugging ========= This section describes debugging techniques for the ESP32-C6. Debugging with ``openocd`` and ``gdb`` -------------------------------------- Espressif uses a specific version of OpenOCD to support ESP32-C6: `openocd-esp32 `_. Please check `Building OpenOCD from Sources `_ for more information on how to build OpenOCD for ESP32-C6. You do not need an external JTAG to debug, the ESP32-C6 integrates a USB-to-JTAG adapter. .. note:: One must configure the USB drivers to enable JTAG communication. Please check `Configure USB Drivers `_ for more information. OpenOCD can then be used:: openocd -s -c 'set ESP_RTOS hwthread' -f board/esp32c6-builtin.cfg -c 'init; reset halt; esp appimage_offset 0x0' .. note:: - ``appimage_offset`` should be set to ``0x0`` when ``Simple Boot`` is used. For MCUboot, this value should be set to ``CONFIG_ESPRESSIF_OTA_PRIMARY_SLOT_OFFSET`` value (``0x10000`` by default). - ``-s `` defines the path to the OpenOCD scripts. Usually set to `tcl` if running openocd from its source directory. It can be omitted if `openocd-esp32` were installed in the system with `sudo make install`. If you want to debug with an external JTAG adapter it can be connected as follows: ============ =========== ESP32-C6 Pin JTAG Signal ============ =========== GPIO4 TMS GPIO5 TDI GPIO6 TCK GPIO7 TDO ============ =========== Furthermore, an efuse needs to be burnt to be able to debug:: espefuse.py -p burn_efuse DIS_USB_JTAG .. warning:: Burning eFuses is an irreversible operation, so please consider the above option before starting the process. OpenOCD can then be used:: openocd -c 'set ESP_RTOS hwtread; set ESP_FLASH_SIZE 0' -f board/esp32c6-ftdi.cfg Once OpenOCD is running, you can use GDB to connect to it and debug your application:: riscv-none-elf-gdb -x gdbinit nuttx whereas the content of the ``gdbinit`` file is:: target remote :3333 set remote hardware-watchpoint-limit 2 mon reset halt flushregs monitor reset halt thb nsh_main c .. note:: ``nuttx`` is the ELF file generated by the build process. Please note that ``CONFIG_DEBUG_SYMBOLS`` must be enabled in the ``menuconfig``. Please refer to :doc:`/quickstart/debugging` for more information about debugging techniques. Stack Dump and Backtrace Dump ----------------------------- NuttX has a feature to dump the stack of a task and to dump the backtrace of it (and of all the other tasks). This feature is useful to debug the system when it is not behaving as expected, especially when it is crashing. In order to enable this feature, the following options must be enabled in the NuttX configuration: ``CONFIG_SCHED_BACKTRACE``, ``CONFIG_DEBUG_SYMBOLS`` and, optionally, ``CONFIG_ALLSYMS``. .. note:: The first two options enable the backtrace dump. The third option enables the backtrace dump with the associated symbols, but increases the size of the generated NuttX binary. Espressif also provides a tool to translate the backtrace dump into a human-readable format. This tool is called ``btdecode.sh`` and is available at ``tools/espressif/btdecode.sh`` of NuttX repository. .. note:: This tool is not necessary if ``CONFIG_ALLSYMS`` is enabled. In this case, the backtrace dump contains the function names. Example - Crash Dump ^^^^^^^^^^^^^^^^^^^^ A typical crash dump, caused by an illegal load with ``CONFIG_SCHED_BACKTRACE`` and ``CONFIG_DEBUG_SYMBOLS`` enabled, is shown below:: riscv_exception: EXCEPTION: Store/AMO access fault. MCAUSE: 00000007, EPC: 420168ac, MT0 riscv_exception: PANIC!!! Exception = 00000007 _assert: Current Version: NuttX 10.4.0 2ae3246e40-dirty Sep 19 2024 14:47:41 risc-v _assert: Assertion failed panic: at file: :0 task: backtrace process: backtrace 0x42016866 up_dump_register: EPC: 420168ac up_dump_register: A0: 0000005a A1: 40809fc4 A2: 00000001 A3: 00000088 up_dump_register: A4: 00007fff A5: 00000001 A6: 00000000 A7: 00000000 up_dump_register: T0: 00000000 T1: 00000000 T2: ffffffff T3: 00000000 up_dump_register: T4: 00000000 T5: 00000000 T6: 00000000 up_dump_register: S0: 4080908e S1: 40809078 S2: 00000000 S3: 00000000 up_dump_register: S4: 00000000 S5: 00000000 S6: 00000000 S7: 00000000 up_dump_register: S8: 00000000 S9: 00000000 S10: 00000000 S11: 00000000 up_dump_register: SP: 4080a020 FP: 4080908e TP: 00000000 RA: 420168ac dump_stack: User Stack: dump_stack: base: 0x40809098 dump_stack: size: 00004040 dump_stack: sp: 0x4080a020 stack_dump: 0x4080a000: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00001880 stack_dump: 0x4080a020: 00000000 40808c90 42016866 42006e06 00000000 00000000 40809078 00000002 stack_dump: 0x4080a040: 00000000 00000000 00000000 42004d72 00000000 00000000 00000000 00000000 stack_dump: 0x4080a060: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 sched_dumpstack: backtrace| 2: 0x420168ac dump_tasks: PID GROUP PRI POLICY TYPE NPX STATE EVENT SIGMASK STACKBASE STACKSIZE COMMAND dump_tasks: ---- --- --- -------- ------- --- ------- ---------- ---------------- 0x40805a90 2048 irq dump_task: 0 0 0 FIFO Kthread - Ready 0000000000000000 0x40807290 2032 Idle_Task dump_task: 1 1 100 RR Task - Waiting Semaphore 0000000000000000 0x408081a8 1992 nsh_main dump_task: 2 2 255 RR Task - Running 0000000000000000 0x40809098 4040 backtrace task sched_dumpstack: backtrace| 0: 0x42008420 sched_dumpstack: backtrace| 1: 0x420089a2 sched_dumpstack: backtrace| 2: 0x420168ac The lines starting with ``sched_dumpstack`` show the backtrace of the tasks. By checking it, it is possible to track the root cause of the crash. Saving this output to a file and using the ``btdecode.sh``:: ./tools/btdecode.sh esp32c6 /tmp/backtrace.txt Backtrace for task 2: 0x420168ac: assert_on_task at backtrace_main.c:158 (inlined by) backtrace_main at backtrace_main.c:194 Backtrace dump for all tasks: Backtrace for task 2: 0x420168ac: assert_on_task at backtrace_main.c:158 (inlined by) backtrace_main at backtrace_main.c:194 Backtrace for task 1: 0x420089a2: sys_call2 at syscall.h:227 (inlined by) up_switch_context at riscv_switchcontext.c:95 Backtrace for task 0: 0x42008420: up_idle at esp_idle.c:74 Peripheral Support ================== The following list indicates the state of peripherals' support in NuttX: ============== ======= ==================== Peripheral Support NOTES ============== ======= ==================== ADC Yes Oneshot and internal temperature sensor AES No Bluetooth No CAN/TWAI Yes DMA Yes ECC No eFuse Yes GPIO Yes Dedicated GPIO supported HMAC No I2C Yes Master and Slave mode also LPI2C supported I2S Yes LED/PWM Yes MCPWM Yes Pulse Counter Yes RMT Yes RNG Yes RSA No RTC Yes SDIO No SHA Yes SPI Yes SPIFLASH Yes SPIRAM No Temp. Sensor No Timers Yes UART Yes LPUART supported USB Serial Yes Watchdog Yes Wi-Fi Yes XTS No ============== ======= ==================== Analog-to-digital converter (ADC) --------------------------------- One ADC unit is available for the ESP32-C6, with 7 channels. During bringup, GPIOs for selected channels are configured automatically to be used as ADC inputs. If available, ADC calibration is automatically applied (see `this page `__ for more details). Otherwise, a simple conversion is applied based on the attenuation and resolution. The ADC unit is accessible using the ADC character driver, which returns data for the enabled channels. The ADC unit can be enabled in the menu :menuselection:`System Type --> Peripheral Support --> Analog-to-digital converter (ADC)`. Then, it can be customized in the menu :menuselection:`System Type --> ADC Configuration`, which includes operating mode, gain and channels. ========== =========== Channel ADC1 GPIO ========== =========== 0 0 1 1 2 2 3 3 4 4 5 5 6 6 ========== =========== .. _MCUBoot and OTA Update C6: MCUBoot and OTA Update ====================== The ESP32-C6 supports over-the-air (OTA) updates using MCUBoot. Read more about the MCUBoot for Espressif devices `here `__. Executing OTA Update -------------------- This section describes how to execute OTA update using MCUBoot. 1. First build the default ``mcuboot_update_agent`` config. This image defaults to the primary slot and already comes with Wi-Fi settings enabled:: ./tools/configure.sh esp32c6-devkitc:mcuboot_update_agent 2. Build the MCUBoot bootloader:: make bootloader 3. Finally, build the application image:: make Flash the image to the board and verify it boots ok. It should show the message "This is MCUBoot Update Agent image" before NuttShell is ready. At this point, the board should be able to connect to Wi-Fi so we can download a new binary from our network:: NuttShell (NSH) NuttX-12.4.0 This is MCUBoot Update Agent image nsh> nsh> wapi psk wlan0 3 nsh> wapi essid wlan0 1 nsh> renew wlan0 Now, keep the board as is and execute the following commands to **change the MCUBoot target slot to the 2nd slot** and modify the message of the day (MOTD) as a mean to verify the new image is being used. 1. Change the MCUBoot target slot to the 2nd slot:: kconfig-tweak -d CONFIG_ESPRESSIF_ESPTOOL_TARGET_PRIMARY kconfig-tweak -e CONFIG_ESPRESSIF_ESPTOOL_TARGET_SECONDARY kconfig-tweak --set-str CONFIG_NSH_MOTD_STRING "This is MCUBoot UPDATED image!" make olddefconfig .. note:: The same changes can be accomplished through ``menuconfig`` in :menuselection:`System Type --> Bootloader and Image Configuration --> Target slot for image flashing` for MCUBoot target slot and in :menuselection:`System Type --> Bootloader and Image Configuration --> Search (motd) --> NSH Library --> Message of the Day` for the MOTD. 2. Rebuild the application image:: make At this point the board is already connected to Wi-Fi and has the primary image flashed. The new image configured for the 2nd slot is ready to be downloaded. To execute OTA, create a simple HTTP server on the NuttX directory so we can access the binary remotely:: cd nuttxspace/nuttx python3 -m http.server Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ... On the board, execute the update agent, setting the IP address to the one on the host machine. Wait until image is transferred and the board should reboot automatically:: nsh> mcuboot_agent http://10.42.0.1:8000/nuttx.bin MCUboot Update Agent example Downloading from http://10.42.0.1:8000/nuttx.bin Firmware Update size: 1048576 bytes Received: 512 of 1048576 bytes [0%] Received: 1024 of 1048576 bytes [0%] Received: 1536 of 1048576 bytes [0%] [.....] Received: 1048576 of 1048576 bytes [100%] Application Image successfully downloaded! Requested update for next boot. Restarting... NuttShell should now show the new MOTD, meaning the new image is being used:: NuttShell (NSH) NuttX-12.4.0 This is MCUBoot UPDATED image! nsh> Finally, the image is loaded but not confirmed. To make sure it won't rollback to the previous image, you must confirm with ``mcuboot_confirm`` and reboot the board. The OTA is now complete. Flash Encryption ---------------- Flash encryption is intended for encrypting the contents of the ESP32-C6's off-chip flash memory. Once this feature is enabled, firmware is flashed as plaintext, and then the data is encrypted in place on the first boot. As a result, physical readout of flash will not be sufficient to recover most flash contents. The current state of flash encryption for ESP32-C6 allows the use of Virtual E-Fuses and development mode, which permit users to evaluate and test the firmware before making definitive changes such as burning E-Fuses. Flash encryption supports the following features: .. list-table:: :header-rows: 1 * - Feature - Description * - **Flash Encryption with Virtual E-Fuses** - Use flash encryption without burning E-Fuses. Default selection when flash encryption is enabled. * - **Flash Encryption in Development mode** - Allows reflashing an encrypted device by appending the ``--encrypt`` argument to the ``esptool.py write_flash`` command. This is done automatically if ``ESPRESSIF_SECURE_FLASH_ENC_FLASH_DEVICE_ENCRYPTED`` is set. * - **Flash Encryption in Release mode** - Does not allow reflashing the device. This is a permanent setting. * - **Flash Encryption key** - A user-generated key is required by default. Alternatively, a device-generated key is possible, but it will not be recoverable by the user (not recommended). See ``ESPRESSIF_SECURE_FLASH_ENC_USE_HOST_KEY``. * - **Encrypted MTD Partition** - If SPI Flash is enabled, an empty user MTD partition will be automatically encrypted on first flash. .. note:: It is **strongly suggested** to read the following before working on flash encryption: - `MCUBoot Flash Encryption `_ - `General E-Fuse documentation `_ - `Flash Encryption Relevant E-Fuses `_ Flash Encryption Requirements ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Flash encryption requires burning E-Fuses to enable it on chip. This is not a reversible operation and should be done with caution. There is, however, a way to test the flash encryption by simulating them on flash. Both paths are described below. Build System Features ''''''''''''''''''''' The build system contains some safeguards to avoid accidentally burning E-Fuses and automations for convenience. Those are summarized below: 1. A yellow warning will show up during build alerting that flash encryption is enabled (same for Virtual E-Fuses). 2. If ``ESPRESSIF_SECURE_FLASH_ENC_USE_HOST_KEY`` is set, build will fail if the flash encryption key is not found. 3. If SPI Flash is enabled, the user MTD partition is automatically encrypted with the provided encryption key. 4. ``make flash`` command will prompt the user for confirmation before burning the E-Fuse, if Virtual E-Fuses are disabled. Simulating Flash Encryption with Virtual E-Fuses ''''''''''''''''''''''''''''''''''''''''''''''''' It is highly recommended to use this method for testing the flash encryption before actually burning the E-Fuses. The E-Fuses are stored in flash and persist between reboots. No real E-Fuses are changed. To enable virtual E-Fuses for flash encryption testing, open ``menuconfig`` and: 1. Enable flash encryption on boot on: :menuselection:`System Type --> Bootloader and Image Configuration` 2. Verify Virtual E-Fuses are enabled (this is done by default): :menuselection:`System Type --> Peripheral Support --> E-Fuse support` Now build the bootloader and the firmware. Flashing the device will trigger the following: 1. On the first boot, the bootloader will encrypt the flash:: ... [esp32c6] [WRN] eFuse virtual mode is enabled. If Secure boot or Flash encryption is enabled then it does not provide any security. FOR TESTING ONLY! [esp32c6] [WRN] [efuse] [Virtual] try loading efuses from flash: 0x10000 (offset) ... [esp32c6] [INF] [flash_encrypt] Encrypting bootloader... [esp32c6] [INF] [flash_encrypt] Bootloader encrypted successfully [esp32c6] [INF] [flash_encrypt] Encrypting primary slot... [esp32c6] [INF] [flash_encrypt] Encrypting remaining flash... [esp32c6] [INF] [flash_encrypt] Flash encryption completed ... [esp32c6] [INF] Resetting with flash encryption enabled... 2. Device will reset and it should be now operating similar to an actual encrypted device:: ... [esp32c6] [INF] Checking flash encryption... [esp32c6] [INF] [flash_encrypt] flash encryption is enabled (1 plaintext flashes left) [esp32c6] [INF] Disabling RNG early entropy source... [esp32c6] [INF] br_image_off = 0x20000 [esp32c6] [INF] ih_hdr_size = 0x20 [esp32c6] [INF] Loading image 0 - slot 0 from flash, area id: 1 ... NuttShell (NSH) NuttX-12.8.0 nsh> Actual encryption and burning E-Fuses ''''''''''''''''''''''''''''''''''''' E-Fuses are burned by esptool and the bootloader on the first boot after flashing with encryption enabled. This process is automated on NuttX build system. .. warning:: Burning E-Fuses is NOT a reversible operation and should be done with caution. To build a firmware with E-Fuse support and flash encryption enabled, open ``menuconfig`` and: 1. Enable flash encryption on boot on: :menuselection:`System Type --> Bootloader and Image Configuration` 2. Disable Virtual E-Fuses :menuselection:`System Type --> Peripheral Support --> E-Fuse support` 3. Check usage mode is Development (this allows reflashing, while Release mode does not). .. note:: If using development mode of flash encryption (see menuconfig and documentation above), it is still possible to re-flash the device with esptool by setting ``ESPRESSIF_SECURE_FLASH_ENC_FLASH_DEVICE_ENCRYPTED`` which adds ``--encrypt`` argument to the ``esptool.py write_flash`` command. This will apply the burned encryption key to the image while flashing. Flash Allocation for MCUBoot ---------------------------- When MCUBoot is enabled on ESP32-C6, the flash memory is organized as follows based on the default KConfig values: **Flash Layout (MCUBoot Enabled)** .. list-table:: :header-rows: 1 :widths: 40 20 20 :align: left * - Region - Offset - Size * - Bootloader - 0x000000 - 64KB * - E-Fuse Virtual (see Note) - 0x010000 - 64KB * - Primary Application Slot (/dev/ota0) - 0x020000 - 1MB * - Secondary Application Slot (/dev/ota1) - 0x120000 - 1MB * - Scratch Partition (/dev/otascratch) - 0x220000 - 256KB * - Storage MTD (optional) - 0x260000 - 1MB * - Available Flash - 0x360000+ - Remaining .. raw:: html
**Note**: The E-Fuse Virtual region is optional and only used when ``ESPRESSIF_EFUSE_VIRTUAL_KEEP_IN_FLASH`` is enabled. However, this 64KB location is always allocated in the memory layout to prevent accidental erasure during board flashing operations, ensuring data preservation if virtual E-Fuses are later enabled. .. code-block:: text Memory Map (Addresses in hex): 0x000000 ┌─────────────────────────────┐ │ │ │ MCUBoot Bootloader │ │ (64KB) │ │ │ 0x010000 ├─────────────────────────────┤ │ E-Fuse Virtual │ │ (64KB) │ 0x020000 ├─────────────────────────────┤ │ │ │ Primary App Slot │ │ (1MB) │ │ /dev/ota0 │ │ │ 0x120000 ├─────────────────────────────┤ │ │ │ Secondary App Slot │ │ (1MB) │ │ /dev/ota1 │ │ │ 0x220000 ├─────────────────────────────┤ │ │ │ Scratch Partition │ │ (256KB) │ │ /dev/otascratch │ │ │ 0x260000 ├─────────────────────────────┤ │ │ │ Storage MTD (optional) │ │ (1MB) │ │ │ 0x360000 ├─────────────────────────────┤ │ │ │ Available Flash │ │ (Remaining) │ │ │ └─────────────────────────────┘ The key KConfig options that control this layout: - ``ESPRESSIF_OTA_PRIMARY_SLOT_OFFSET`` (default: 0x20000) - ``ESPRESSIF_OTA_SECONDARY_SLOT_OFFSET`` (default: 0x120000) - ``ESPRESSIF_OTA_SLOT_SIZE`` (default: 0x100000) - ``ESPRESSIF_OTA_SCRATCH_OFFSET`` (default: 0x220000) - ``ESPRESSIF_OTA_SCRATCH_SIZE`` (default: 0x40000) - ``ESPRESSIF_STORAGE_MTD_OFFSET`` (default: 0x260000 when MCUBoot enabled) - ``ESPRESSIF_STORAGE_MTD_SIZE`` (default: 0x100000) For MCUBoot operation: - The **Primary Slot** contains the currently running application - The **Secondary Slot** receives OTA updates - The **Scratch Partition** is used by MCUBoot for image swapping during updates - MCUBoot manages image validation, confirmation, and rollback functionality .. _esp32c6_ulp: ULP LP Core Coprocessor ======================= The ULP LP core (Low-power core) is a 32-bit RISC-V coprocessor integrated into the ESP32-C6 SoC. It is designed to run independently of the main high-performance (HP) core and is capable of executing lightweight tasks such as GPIO polling, simple peripheral control and I/O interactions. This coprocessor benefits to offload simple tasks from HP core (e.g., GPIO polling , I2C operations, basic control logic) and frees the main CPU for higher-level processing For more information about ULP LP Core Coprocessor `check here `__. Features of the ULP LP-Core --------------------------- * Processor Architecture - RV32I RISC-V core with IMAC extensions—Integer (I), Multiplication/Division (M), Atomic (A), and Compressed (C) instructions - Runs at 20 MHz * Memory - Access to 16 KB of low-power memory (LP-RAM) and LP-domain peripherals any time - Full access to all of the chip's memory and peripherals when when the HP core is active * Debugging - Built-in JTAG debug module for external debugging - Supports LP UART for logging from the ULP itself - Includes a panic handler capable of dumping register state via LP UART on exceptions * Peripheral support - LP domain peripherals (LP GPIO, LP I2C, LP UART and LP Timer) - Full access HP domain peripherals when when the HP core is active Loading Binary into ULP LP-Core ------------------------------- There are two ways to load a binary into LP-Core: - Using a prebuilt binary - Using NuttX internal build system to build your own (bare-metal) application When using a prebuilt binary, the already compiled output for the ULP system whether built from NuttX or the ESP-IDF environment can be leveraged. However, whenever the ULP code needs to be modified, it must be rebuilt separately, and the resulting .bin file has to be integrated into NuttX. This workflow, while compatible, can become tedious. With NuttX internal build system, the ULP binary code can be built and flashed from a single location. It is more convenient but using build system has some dependencies on example side. Both methods requires ``CONFIG_ESPRESSIF_USE_LP_CORE`` variable to enable ULP core and it can be set using ``make menuconfig`` or ``kconfig-tweak`` commands. Additionally, a Makefile needs to be provided to specify the ULP application name, source path of the ULP application, and either the binary (for prebuilt) or the source files (for internal build). This Makefile must include the ULP makefile after the variable set process on ``arch/risc-v/src/common/espressif/esp_ulp.mk`` integration script. For more information please refer to :ref:`ulp example Makefile. ` Makefile Variables for ULP Core Build: -------------------------------------- - ``ULP_APP_NAME``: Sets name for the ULP application. This variable also be used as prefix (e.g. ULP application bin variable name) - ``ULP_APP_FOLDER``: Specifies the directory containing the ULP application's source codes. - ``ULP_APP_BIN``: Defines the path of the prebuilt ULP binary. - ``ULP_APP_C_SRCS``: Lists all C source files (.c) that need to be compiled for the ULP application. - ``ULP_APP_ASM_SRCS``: Lists all assembly source files (.S or .s) to be assembled. - ``ULP_APP_INCLUDES``: Specifies additional include directories for the compiler and assembler. Here is an Makefile example when using prebuilt binary for ULP core: .. code-block:: console ULP_APP_NAME = esp_ulp ULP_APP_FOLDER = $(TOPDIR)$(DELIM)arch$(DELIM)$(CONFIG_ARCH)$(DELIM)src$(DELIM)$(CHIP_SERIES) ULP_APP_BIN = $(TOPDIR)$(DELIM)Documentation$(DELIM)platforms$(DELIM)$(CONFIG_ARCH)$(DELIM)$(CONFIG_ARCH_CHIP)$(DELIM)boards$(DELIM)$(CONFIG_ARCH_BOARD)$(DELIM)ulp_riscv_blink.bin include $(TOPDIR)$(DELIM)arch$(DELIM)$(CONFIG_ARCH)$(DELIM)src$(DELIM)common$(DELIM)espressif$(DELIM)esp_ulp.mk Here is an example for enabling ULP and using the prebuilt test binary for ULP core:: make distclean ./tools/configure.sh esp32c6-devkitc:nsh kconfig-tweak -e CONFIG_ESPRESSIF_USE_LP_CORE kconfig-tweak -e CONFIG_ESPRESSIF_ULP_USE_TEST_BIN make olddefconfig make -j Creating an ULP LP-Core Application ----------------------------------- To use NuttX's internal build system to compile the bare-metal LP binary, check the following instructions. First, create a folder for the ULP source and header files into your NuttX example. This folder is just for ULP project and it is an independent project. Therefore, the NuttX example guide should not be followed for ULP example (folder location is irrelevant. It can be the same of the `nuttx-apps` repository, for instance). To include the ULP folder in the build system, don't forget to include the ULP Makefile in the NuttX example Makefile. Lastly, configuration variables needed to enable ULP core instructions can be found above. NuttX's internal functions or POSIX calls are not supported. Here is an example: - ULP UART Snippet: .. code-block:: C #include #include "ulp_lp_core_print.h" #include "ulp_lp_core_utils.h" #include "ulp_lp_core_uart.h" #include "ulp_lp_core_gpio.h" #define nop() __asm__ __volatile__ ("nop") int main (void) { while(1) { lp_core_printf("Hello from the LP core!!\r\n"); for (int i = 0; i < 10000; i++) { nop(); } } return 0; } For more information about ULP Core Coprocessor examples `check here `__. After these settings follow the same steps as for any other configuration to build NuttX. Build system checks ULP project path, adds every source and header file into project and builds it. To sum up, here is an example. ``ulp_example/ulp (../ulp_example/ulp)`` folder selected as example to create a subfolder for ULP but folder that includes ULP source code can be anywhere. For more information about custom apps, please follow NuttX `Custom Apps How-to `__ guide, this example will demonstrate how to add ULP code into a custom application: - Tree view: .. code-block:: text nuttxspace/ ├── nuttx/ └── apps/ └── ulp_example/ └── Makefile └── Kconfig └── ulp_example.c └── ulp/ └── Makefile └── ulp_main.c - Contents in Makefile: .. code-block:: console include $(APPDIR)/Make.defs PROGNAME = $(CONFIG_EXAMPLES_ULP_EXAMPLE_PROGNAME) PRIORITY = $(CONFIG_EXAMPLES_ULP_EXAMPLE_PRIORITY) STACKSIZE = $(CONFIG_EXAMPLES_ULP_EXAMPLE_STACKSIZE) MODULE = $(CONFIG_EXAMPLES_ULP_EXAMPLE) MAINSRC = ulp_example.c include $(APPDIR)/Application.mk include ulp/Makefile - Contents in Kconfig: .. code-block:: console config EXAMPLES_ULP_EXAMPLE bool "ULP Example" default n - Contents in ulp_example.c: .. code-block:: C #include #include #include #include #include #include #include #include #include "ulp/ulp/ulp_main.h" /* Files that holds ULP binary header */ #include "ulp/ulp/ulp_code.h" int main (void) { int fd; fd = open("/dev/ulp", O_WRONLY); if (fd < 0) { printf("Failed to open ULP: %d\n", errno); return -1; } /* ulp_example is the prefix which can be changed with ULP_APP_NAME makefile * variable to access ULP binary code variable */ write(fd, ulp_example_bin, ulp_example_bin_len); return 0; } .. _ulp_makefile: - Contents in ulp/Makefile: .. code-block:: console ULP_APP_NAME = ulp_example ULP_APP_FOLDER = $(APPDIR)$(DELIM)ulp_example$(DELIM)ulp ULP_APP_C_SRCS = ulp_main.c include $(TOPDIR)$(DELIM)arch$(DELIM)$(CONFIG_ARCH)$(DELIM)src$(DELIM)common$(DELIM)espressif$(DELIM)esp_ulp.mk - Contents in ulp_main.c: .. code-block:: C #include #include #include "ulp_lp_core_gpio.h" #define GPIO_PIN 0 #define nop() __asm__ __volatile__ ("nop") bool gpio_level_previous = true; int main (void) { while (1) { ulp_lp_core_gpio_set_level(GPIO_PIN, gpio_level_previous); gpio_level_previous = !gpio_level_previous; for (int i = 0; i < 10000; i++) { nop(); } } return 0; } - Command to build:: make distclean ./tools/configure.sh esp32c6-devkitc:nsh kconfig-tweak -e CONFIG_ESPRESSIF_GPIO_IRQ kconfig-tweak -e CONFIG_DEV_GPIO kconfig-tweak -e CONFIG_ESPRESSIF_USE_LP_CORE kconfig-tweak -e CONFIG_EXAMPLES_ULP_EXAMPLE make olddefconfig make -j Here is an example of a single ULP application. However, support is not limited to just one application. Multiple ULP applications are also supported. By following the same guideline, multiple ULP applications can be created and loaded using ``write`` POSIX call. Each NuttX application can build one ULP application. Therefore, to build multiple ULP applications, multiple NuttX applications are needed to create each ULP binary. This limitation only applies when using the NuttX build system to build multiple ULP applications; it does not affect the ability to load multiple ULP applications built by other means. ULP binary can be included in NuttX application by adding ``#include "ulp/ulp/ulp_code.h"`` line. Then, the ULP binary is accessible by using the ULP application prefix (defined by the ``ULP_APP_NAME`` variable in the ULP application Makefile) with the ``bin`` keyword to access the binary data (e.g., if ``ULP_APP_NAME`` is ``ulp_test``, the binary variable will be ``ulp_test_bin``) and ``bin_len`` keyword to access its length (e.g., ``ulp_test_bin_len`` for ``ULP_APP_NAME`` is ``ulp_test``). Accessing the ULP LP-Core Program Variables ------------------------------------------- Global symbols defined in the ULP application are available to the HP core through a shared memory region. To read or write ULP variables, direct reading/writing to such memory positions are not allowed. POSIX calls are needed instead. To access the ULP variable through the HP core, consider that its name is defined by the ULP application prefix (defined by the ``ULP_APP_NAME`` variable in the ULP application Makefile) + the ULP application variable. For example if HP core tries to access a ULP application variable named ``result`` and ``ULP_APP_NAME`` in the ULP application Makefile set as ``ulp_app``, required name for that variable will be ``ulp_app_result``. ``FIONREAD`` or ``FIONWRITE`` ioctl calls are, then, performed with the address of a ``struct symtab_s`` previously defined with the name of the variable to be read or written. .. warning:: Ensure that the related ULP application is running. Otherwise, another ULP application may interfere by using the same memory space for a different variables. Here is a snippet for reading and writing to a ULP variable named ``var_test`` (assuming the ``ULP_APP_NAME`` is set to ``ulp``) through the HP core: .. code-block:: C #include #include #include #include #include #include "nuttx/symtab.h" int main (void) { uint32_t ulp_var; int fd; struct symtab_s sym = { .sym_name = "ulp_var_test", .sym_value = &ulp_var, }; fd = open("/dev/ulp", O_RDWR); ioctl(fd, FIONREAD, &sym); if (ulp_var != 0) { ulp_var = 0; ioctl(fd, FIONWRITE, &sym); } return OK; } Debugging ULP LP-Core --------------------- To debug ULP LP-Core please first refer to :ref:`Debugging section. ` Debugging ULP core consist same steps with some small differences. First of all, configuration file needs to be changed from ``board/esp32c6-builtin.cfg`` or ``board/esp32c6-ftdi.cfg`` to ``board/esp32c6-lpcore-builtin.cfg`` or ``board/esp32c6-lpcore-ftdi.cfg`` depending on preferred debug adapter. LP core supports limited set of HW exceptions, so, for example, writing at address 0x0 will not cause a panic as it would be for the code running on HP core. This can be overcome to some extent by enabling undefined behavior sanitizer for LP core application, so ubsan can help to catch some errors. But note that it will increase code size significantly and it can happen that application won't fit into RTC RAM. To enable ubsan for ULP please add ``CONFIG_ESPRESSIF_ULP_ENABLE_UBSAN`` in menuconfig. _`Managing esptool on virtual environment` ========================================== This section describes how to install ``esptool``, ``imgtool`` or any other Python packages in a proper environment. Normally, a Linux-based OS would already have Python 3 installed by default. Up to a few years ago, you could simply call ``pip install`` to install packages globally. However, this is no longer recommended as it can lead to conflicts between packages and versions. The recommended way to install Python packages is to use a virtual environment. A virtual environment is a self-contained directory that contains a Python installation for a particular version of Python, plus a number of additional packages. You can create a virtual environment for each project you are working on, and install the required packages in that environment. Two alternatives are explained below, you can select any one of those. Using pipx (recommended) ------------------------ ``pipx`` is a tool that makes it easy to install Python packages in a virtual environment. To install ``pipx``, you can run the following command (using apt as example):: $ apt install pipx Once you have installed ``pipx``, you can use it to install Python packages in a virtual environment. For example, to install the ``esptool`` package, you can run the following command:: $ pipx install esptool This will create a new virtual environment in the ``~/.local/pipx/venvs`` directory, which contains the ``esptool`` package. You can now use the ``esptool`` command as normal, and so will the build system. Make sure to run ``pipx ensurepath`` to add the ``~/.local/bin`` directory to your ``PATH``. This will allow you to run the ``esptool`` command from any directory. Using venv (alternative) ------------------------ To create a virtual environment, you can use the ``venv`` module, which is included in the Python standard library. To create a virtual environment, you can run the following command:: $ python3 -m venv myenv This will create a new directory called ``myenv`` in the current directory, which contains a Python installation and a copy of the Python standard library. To activate the virtual environment, you can run the following command:: $ source myenv/bin/activate This will change your shell prompt to indicate that you are now working in the virtual environment. You can now install packages using ``pip``. For example, to install the ``esptool`` package, you can run the following command:: $ pip install esptool This will install the ``esptool`` package in the virtual environment. You can now use the ``esptool`` command as normal. When you are finished working in the virtual environment, you can deactivate it by running the following command:: $ deactivate This will return your shell prompt to its normal state. You can reactivate the virtual environment at any time by running the ``source myenv/bin/activate`` command again. You can also delete the virtual environment by deleting the directory that contains it. Supported Boards ================ .. toctree:: :glob: :maxdepth: 1 boards/*/*