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/v12.3.0-2/xpack-riscv-none-elf-gcc-12.3.0-2-linux-x64.tar.gz" \
| tar -C riscv-none-elf-gcc --strip-components 1 -xz

It uses the xPack’s prebuilt toolchain based on GCC 12.3.0.

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/v12.3.0-2/xpack-riscv-none-elf-gcc-12.3.0-2-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 and partition table

The NuttX port for now relies on IDF’s second stage bootloader to carry on some hardware initializations. The binaries for the bootloader and the partition table can be found in this repository: https://github.com/espressif/esp-nuttx-bootloader That repository contains a dummy IDF project that’s used to build the bootloader and partition table, these are then presented as Github assets and can be downloaded from: https://github.com/espressif/esp-nuttx-bootloader/releases Download bootloader-esp32c6.bin and partition-table-esp32c6.bin and place them in a folder, the path to this folder will be used later to program them. This can be: ../esp-bins

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 or ./tools/configure.sh esp32c6-devkitm:nsh``Run ``make to build the project. Note that the conversion mentioned above is included in the build process. The esptool.py command to flash all the binaries is:

esptool.py --chip esp32c6 --port /dev/ttyUSBXX --baud 921600 write_flash 0x0 bootloader.bin 0x8000 partition-table.bin 0x10000 nuttx.bin

However, this is also included in the build process and we can build and flash with:

make flash ESPTOOL_PORT=<port> ESPTOOL_BINDIR=../esp-bins

Where <port> is typically /dev/ttyUSB0 or similar and ../esp-bins is the path to the folder containing the bootloader and the partition table for the ESP32-C6 as explained above. Note that this step is required only one time. Once the bootloader and partition table are flashed, we don’t need to flash them again. So subsequent builds would just require: make flash ESPTOOL_PORT=/dev/ttyUSBXX

Debugging with OpenOCD

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

You don not need an external JTAG is 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