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Installing Apache NuttX POSIX embedded OS on RISC-V based ESP32-C3 with Arch Linux

Table of content

Apache NuttX logo
* Introduction
* System packages
* NuttX sources and tools
* Configuration of devkit project, compilation and flash
* Connexion to NSH via (USB) serial
* The ostest and other basic sets (UPDATE)
* The apps examples (UPDATE)
* GPIO (UPDATE)
* SPIflash, SMARTFS and file fsystems (UPDATE)
* TMPFS (UPDATE)
* NSH scripting (UPDATE)

Introduction

Apache NuttX is a POSIX embedded system available on a lot of microcontrollers boards and architectures. After seeing some articles from Lup Yuen Lee, installing and working with NuttX on Bouffalo BL602 and BL604 RISC-V microcontroller boards, I discovered it can be installed on one of my boards. So I tried and managed to install it this evening on my recently acquired 3.5€ ESP32-C3S SoC nodeMCU board. ESP32-C3 is a SoC with RISC-V RV32IMC microcontroller, integrated 2.4GHz WiFi and Bluetooth LTE. The board contains a CH340 serial-USB converter, so it can easily be used/flashed/debugged from a computer. I already made a post about installing ESP-IDF tools and flashing examples on this RISC-V board.

For people that already know Espressif SoCs, here is a table of the power usage of some of their ESP models:

SoC        Modem sleep  Light sleep mode  Deep sleep mode
ESP8266          20 mA          2,000 µA            20 µA
ESP32            20 mA            800 µA            20 µA
ESP32-C3         20 mA            130 µA             5 µA

This article explains the procedure to prepare environment, on Arch Linux in November 2021. This is for x86_64, but should work on ARM too, only RISC-V toolchains are missing on ALARM, can be compiled, by using x86_64 versions of PKGBUILD (riscv32-elf-binutils, riscv64-elf-gcc). You can find the pricompiled binaries in my ArchLinux ARM archives including a little text about the order of compilation (binlib, gcc-bootstrap, newlib, gcc (and optionnaly, gcc and newlib again). Direct link to the three most usefull archives:
* riscv32-elf-binutils-2.36.1-2-armv7h.pkg.tar.xz
* riscv64-elf-gcc-11.1.0-1-armv7h.pkg.tar.xz
* riscv64-elf-newlib-4.1.0-1-any.pkg.tar.xz

Latest GIT version is needed In November 2021 for ESP32-C3, some other RISC-V architectures are already in stable releases. This is followed by an example of flashing and connect to the NSH shell, via serial on USB terminal. The dependencies for Debian based Linux on the official page, some parts could be incomplete. Some aspects of the NuttX, POSIX compatible Filesystem. OStest, GPIO and SPIflash included examples are also shortly described. Continue reading

Using ESP-IDF with RISC-V ESP32-C3 nodeMCU module on a Linux system

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<h2 id=Table of Content

* Introduction
* Step 1, install dependencies
* Step 2, install ESP-IDF
* Step 3, setup working environment
* Step 4, test “Hello World” example
* Step 5, tune the target, if needed
* Step 6, flash the project
* Step 7, viewing the output
* Troubleshooting
** Invalid value for ‘{esp32|esp32s2}’: ‘esp32c3′ is not one of ‘esp32′, ‘esp32s2′
** libsodium/crypto_box/curve25519xchacha20poly1305/box_seal_curve25519xchacha20poly1305.c
** Flashing errors
*** Detection, power, and device that disappear
*** usbfs: interface 0 claimed by ch341 while ‘brltty’ sets config #1
** Problem with CA certificates bundle

Introduction

The list of existing ESP32-C3 SoC modules (with their specs) is very interesting, This one RISC-V core SoC has lower computing power than the ESP32-S3 (dual-core Xtensa ISA based, with a RISC-V co-processor core for “ultra low power” (ULP) mode), but RISC-V architecture is also far more efficient and will for sure have longer lifetime support and evolution due to its openness. ESP32-C3 use an RV32IMC (Integer, Multiplication/division and Compressed extensions) core.

I bought for my test a ESP-C3-32S-Kit on AliExpress (for ~3.4€). There is also an interesting option, where you can use really tiny 3~4 € ESP-C3-01M-Kit programmer interface/mother board, with a SoC included alone on a daughter (ESP32-C3M with an on PCB antenna). This allows, to flash several pads one only one programmer board. This reduce size of the needed system for final application to just the SoC and it’s power supply and peripherals. Pads of the SoC daughter board are wide enough to be easily soldered.

ESP-IDF is a tool to develop in C language on Espressif platforms, including ESP8266 and ESP32 series. It uses FreeRTOS free and open source embedded real-time OS for its SoCs. Sadly the official documentation for installing it is incomplete with the current state (November 2021) of GIT repository. Here is the mean to install a working ESP-IDF for this SoC series on Linux. This will be more compact and straight forward that the official with Linux+Windows installation.

About RISC-V more generally, I created this week a list of available Open Source RISC-V implementations, and open sources tools to build them or work with them. Continue reading

Short and practical introduction to FPGA, Verilog and Verilator and few words about SystemVerilog

→ Version en français ici

Warning, I’m a less than one month beginner in Verilog, Verilator et FPGA, studied as a hobby, if there are some mistakes I will correct it. You can contact me on The Fediverse.

Table of Content


* Introduction
** Real world full process
** Things to know and understand
** How to code a FPGA
* Verilog
** Values
** Types
** Gates
** Modules
** Simple example, writing an “and” gate
** Initial and always blocks
* Simple example with Verilator
** Make the test with Verilator
** Tracing example and GTKWave
** About Verilator examples
** Basic practical example with Verilator
* Further reading

The text in strong are here to help diagonal reading.

Introduction

Still continue to go to lower layers with the world of FPGA (Field Processors Gateway Array). This is a reprogrammable development electronic tool used to build and test processor. After the processor is validated in FPGA, you can start to build ASIC (Application-specific integrated circuit), actual hardwired processors that we use every-days in our computing devices. FPGA are also used as is in several industrial appliance (avionics, audio or video processing, etc…) for their parallelism, so the fact they are faster than a general purpose ASIC and a piece of software in these cases, and the ability to update them easily in case of problem. This post is a little introduction about FPGA, the popular IEEE standard Verilog HDL (“Hardware description language”) language and how to test it with free and open source software (FOSS) Verilator simulator. If you want to use VHDL, GHDL is FOSS simulator for VHDL.

Continue reading