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:

###############################################################################
# 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:

$ mkdir -p /path/to/your/toolchain/riscv-none-elf-gcc

Download and extract toolchain:

$ 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:

$ 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.

Second stage bootloader

Nuttx can boot the ESP32-H2 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).

Building and flashing

First, make sure that esptool.py is installed. 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.

Configure the NuttX project: ./tools/configure.sh esp32c6-devkitc:nsh Run make to build the project. Note that the conversion mentioned above is included in the build process. The esptool.py is used to flash all the binaries. However, this is also included in the build process and we can build and flash with:

make flash ESPTOOL_PORT=<port> ESPTOOL_BINDIR=./

Where <port> is typically /dev/ttyUSB0 or similar and ./ is the path to the folder containing the externally-built 2nd stage bootloader for the ESP32-C6 as explained above.

Debugging with OpenOCD

Download and build OpenOCD from Espressif, that can be found in https://github.com/espressif/openocd-esp32

You do not need an external JTAG to debug, the ESP32-C6 integrates a USB-to-JTAG adapter.

OpenOCD can then be used:

openocd -c 'set ESP_RTOS none' -f board/esp32c6-builtin.cfg

If you want to debug with an external JTAG adapter it can be connected as follows:

TMS -> GPIO4
TDI -> GPIO5
TCK -> GPIO6
TDO -> GPIO7

Furthermore, an efuse needs to be burnt to be able to debug:

espefuse.py -p <port> burn_efuse DIS_USB_JTAG