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.

Building and flashing NuttX

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).

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==4.8.dev4.

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 hwthread; set ESP_FLASH_SIZE 0' -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

OpenOCD can then be used:

openocd  -c 'set ESP_RTOS hwtread; set ESP_FLASH_SIZE 0' -f board/esp32c6-ftdi.cfg

Peripheral Support

The following list indicates the state of peripherals’ support in NuttX:

Peripheral

Support

ADC

No

AES

No

Bluetooth

No

CAN/TWAI

Yes

DMA

No

ECC

No

eFuse

No

GPIO

Yes

HMAC

No

I2C

No

I2S

No

Int. Temp.

No

LED

No

LED_PWM

Yes

MCPWM

No

Pulse Counter

No

RMT

No

RNG

No

RSA

No

RTC

Yes

SD/MMC

No

SDIO

No

SHA

No

SPI

Yes

SPIFLASH

Yes

Timers

Yes

UART

Yes

Watchdog

Yes

Wifi

Yes

XTS

No

Supported Boards