c3dk

A bare metal, single header make-based SDK for the ESP32-C3 chip.

This code was adapted from cpq/mdk and extended to be used in my bachelor's thesis "On the Power Estimation of a RISC-V Platform using Performance Monitoring Counters and RTOS Events."

File overview

c3dk consists of the following files:

• link.ld: linker script file, allows registers to be memory mapped.
• boot.c: simple startup code. Sets up a stack, calls main()
• c3dk.h: primary header that implements API
• build.mk: helper Makefile for building projects

Installation & Usage

A Linux System with Podman or Docker is required.

To build software, create a Makefile with at least the following contents:

SOURCES = main.c, other.c
SDK = /path/to/c3dk
include $(SDK)/build.mk

Toolchain

c3dk builds images in a custom Debian container which contains a GCC multilib toolchain¹ tailored specifically to the ESP32-C3's application binary interface (ABI), allowing, for example, for complete softfloat and math.h support.

The toolchain resides in /opt in conjunction with the newlib C library.

Note

The initial local build may take considerable time and disk space, but will be efficiently cached thanks to multi-stage builds.

A pre-built container on GitHub is hosted via ghcr.io/j0hax/c3dk:nightly.

Differences from MDK

I am very appreciative of the hard work that has been done in MDK. The project has, however, seen little maintenance over the past two years. I have opened some Pull Requests without response, prompting me to hard-fork and rebrand the project. Some notable differences include that:

• This fork focusses on the ESP32-C3 exclusively.
• cpq/esputil is not used: The utility did not support flashing over JTAG, and the images built did not have headers adapted to the ESP32-C3. As a result, I recommend using ESP's official esptool.
• Extended API
• Extended linker script

Aside from changed variable names, the project should mostly be backward-compatible with MDK. Windows and macOS support is untested.

Footnotes

1. The ESP32-C3 needs a rv32imc_zicsr/ilp32 multilib, a combination which is not built in most GCC RISC-V distributions as of August 2024. ↩