While the vanilla Espressif SDK ships with a number of blobs, there is also an open SDK already. Let’s have a look at the details.
The gcc backend for the Xtensa is probably fully open as one could deduce from Using the GNU Compiler Collection (GCC): Xtensa Options and
While most of its source code is open, there are some closed-source proprietary blobs from Espressif required to run any programs on the chip.
Q: What are these proprietary blobs?
[…] which pulls down all submodules that the framework depends on: in this case some binary blob libraries in
components/bt/libas well as the
esptool.pyprogram that will actually flash the chip for us.
A: It’s the WiFi and Bluetooth software stack.
This repository provides the integration scripts to build a complete standalone SDK (with toolchain) for software development with the Espressif ESP8266 and ESP8266EX chips.
The ESP8266 Wiki references the
which provides the integration scripts to build a complete standalone SDK (with toolchain) for software development with the Espressif ESP chips.