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).
If other features are required, an externally-built 2nd stage bootloader is needed.
The 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.
$ esptool.py erase_flash
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 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 -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:
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 <port> 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 Debugging for more information about debugging techniques.
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 |
Yes |
ECC |
No |
eFuse |
No |
GPIO |
Yes |
HMAC |
No |
I2C |
Yes |
I2S |
No |
Int. Temp. |
No |
LED |
No |
LED_PWM |
Yes |
MCPWM |
Yes |
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 |