Espressif ESP32-C3
The ESP32-C3 is an ultra-low-power and highly integrated SoC with a RISC-V core and supports 2.4 GHz Wi-Fi and Bluetooth Low Energy.
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 - 384 KB ROM - 400 KB SRAM (16 KB can be configured as Cache) - 8 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-C3 Toolchain
A generic RISC-V toolchain can be used to build ESP32-C3 projects. SiFive’s toolchain can be downloaded from: https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.3.0-2019.08.0-x86_64-linux-ubuntu14.tar.gz
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-esp32c3.bin and partition-table-esp32c3.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 image and to flash the image into the board.
It can be installed with: pip install esptool.
Configure the NUttX project: ./tools/configure.sh esp32c3-devkit: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 esp32c3 --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-C3 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
If you have an ESP32-C3 ECO3, no external JTAG is required to debug, the ESP32-C3 integrates a USB-to-JTAG adapter.
OpenOCD can then be used:
openocd -c 'set ESP_RTOS none' -f board/esp32c3-builtin.cfg
For versions prior to ESP32-C3 ECO3, an external JTAG adapter is needed. 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 none' -f board/esp32c3-ftdi.cfg
Peripheral Support
The following list indicates the state of peripherals’ support in NuttX: