Benjamin Cabé

It has been way too long since I posted a Zephyr Weekly Update, so let’s try to get back to a more regular schedule, shall we? The past few weeks have been very busy for the Zephyr community as the new Long-Term Support version of the project, Zephyr 3.7 was just released.

It is a big milestone for the project and it brings a lot of new features and improvements which I’ve been covering in details in last week’s announcement blog post. I also had a lot of fun diving into some of the most significant changes and putting together this video that’s packed with in-depth demos of the new HTTP Server, Precision Time Protocol integration, and more.

As for this week’s news, just keep reading!

Rust coming to Zephyr?

The first few weeks after a major release are the perfect time for new significant features to be proposed, and this is exactly what is happening right now with the proposal to add Rust support to Zephyr.

RFC #65837 describes the bulk of the proposal and there’s now a number of pull requests with actual code and documentation that I highly encourage everyone to give a try.

#![no_std]

use zephyr::printkln;

extern crate zephyr;

#[no_mangle]
extern "C" fn rust_main() {
    printkln!("Hello world from Rust on {}",
              zephyr::kconfig::CONFIG_BOARD);
}

I am really excited to see all the work and discussions happening around the topic as this will be my excuse to finally learn Rust!

Interesting, and related: as of this week, probe-rs is a new supported runner which you can use to flash/debug a supported board. (PR #71627)

Upcoming Zephyr Tech Talk

Join me on Wednesday, August 7 (3.oo pm CEST / 9.00 am EDT) for a new Zephyr Tech Talk live stream! Katarzyna Zalewska will be back on the show and we will be discussing some of the best practices for monitoring the health of IoT devices in realtime.

You may join us from YouTube or LinkedIn, whichever you prefer 🙂

Boards & SoCs

Not an exhaustive list, but some of the new boards and shields recently added are:

• Added support for the Nucleo-H503RB board (PR #75590)
• Added support for Mikroe BLE TINY Click shield. (PR #76246)
• Added support for Adafruit Feather nrf52840 Sense. (PR #76135)

Drivers

• New driver for ST LSM9DS1 9-DOF IMU. (PR #73141)
• New RTC driver for Micro Crystal RV-8263-C8 . (PR #73385)
• New driver for Infineon CAT1 QSPI flash controller. (PR #73976)
• New True-RNG driver for Analog Device MAX32xxx SoC series. (PR #74943)

Miscellaneous

• HTTP server now allows to serve static resources directly from the file system. The content type of the resource is auto-guessed based on the file extension, and .gz files are also automatically treated as compressed content and HTTP headers set accordingly. Neat! (PR #76106)
• Emulated UART devices can now be added to a zephyr,uart-emul UART controller. (PR #75827)
• New LwM2M shell command (obs) to dig into active observations. (PR #74293)

A big thank you to the 23 individuals who had their first pull request accepted since Zephyr 3.7 was released, 💙 🙌: @jacobw, @bas-archembedded, @dberlin, @alexstanoev-nordic, @maarten1C96, @SandraArrow, @Finwood, @juliaazziz, @LeoBRIANDSmile, @Finomnis, @anobli, @gschwaer, @WalkingTalkingPotato, @florolf, @thales-nascimento, @mrodgers-witekio, @VineetaNarkhede-eaton, @GaofengZhangNXP, @munir-zin, @olivier-le-sage, @00thirdeye00, @nordic-pikr, and @jsarha.

As always, I very much welcome your thoughts and feedback in the comments below!

If you enjoyed this article, don’t forget to subscribe to this blog to be notified of upcoming publications! And of course, you can also always find me on Twitter and Mastodon.

Catch up on all previous issues of the Zephyr Weekly Update:

Before diving into this week’s updates, a quick reminder about our upcoming Zephyr Tech Talk, next Thursday, May 30!
We will be discussing all things tracing and profiling, and I am really looking forward to seeing lots of live demos of some of the tools available out there that can really help you understand better what’s really going on under the hood of your favorite RTOS, as well as potentially identify performance bottlenecks.

MQTT-based sensor/actuator code samples

We have a new code sample that might be one of the most comprehensive to date in the Zephyr tree.

It demonstrates how to implement a simple IoT sensor that publishes sensor data over MQTT. IoT 101, you might say, but the sample is a great showcase of the many services one needs to support such a scenario, among which:

• Establishing network connectivity using DHCP ;
• Establishing a secure MQTT connection (using TLS 1.2) ;
• Using JSON to encode sensor data and send it at a user-defined interval (would be curious to see CBOR or other encoding formats introduced as alternatives) ;
• Subscribing to user-defined topic(s) on the MQTT server, e.g. to receive commands ;
• etc.

New SoC porting guide

A new documentation page describes the process of porting a new SoC to Zephyr.

This is a most welcome addition, that complements the existing architecture and board porting guides, and will be very useful for anyone looking to add support for a new SoC to Zephyr. (PR #69475)

Boards & SoCs

• Several additions to the list of peripherals supported for Renesas Smartbond SoCs: memory controller, added power management support to the crypto and MIPI DBI driver, … (PR #68023, #72994, #72819)
• Apollo 3 SoC series getting some love as well, with new counter driver (PR #72842), I2C (PR #72913), and watchdog (PR #72830)
• Added support for NXP Kinetis KE1xZ series. KE1xZ MCUs are based on a Cortex-M0+ core, running up to 96 MHz. These MCUs support up to 512 KB flash, 96 KB RAM, and a complete set of analog/digital features. (PR #71670)
• Added support for Microchip MEC5 SoC family. (PR #72876)

New boards and shields:

• Added support for NXP FRDM-RW612 board.
  The RW612 is a highly integrated, low-power tri-radio wireless MCU with an integrated 260 MHz ARM Cortex-M33 MCU and Wi-Fi 6 + Bluetooth Low Energy (LE) 5.3 / 802.15.4 radios. (PR #72306)
• Alongside KE1xZ SoC support, the NXP FRDM-KE15Z is now also supported. It contains a robust TSI (touch sensing interface) module with up to 50 channels, making it highly flexible for handling touch keys.
• USB device controller now available for nRF54H20 DK. (PR #72774)

Drivers

• It seems like the Video subsystem is getting some attention recently, and it is really nice to see a new driver just landed for the OV5640 CMOS 5-Megapixel image sensor. (PR #71854)
• New driver for Festo VEAA-X-3 series proportional pressure regulator. (PR #69047)
• New LED Strip driver for Texas Instruments TLC59731. TLC59731 is a 3-channel, 8-bit, PWM LED driver with single-wire interface based on the EasySet protocol. (PR #68617)

Miscellaneous

• A new rtt-console snippet has been introduced to quickly switch serial console output to Segger J-Link RTT.
• When using the sensor_shell code sample, you can now include a fake sensor implementation, which can help when you don’t have an actual sensor at hand 🙂 (PR #72833)
• You may now enable CONFIG_EXCEPTION_STACK_TRACE_SYMTAB to have symbol names printed in stack traces on Arm64 and RISC-V. (PR #72973)
• Added a new module implementing MIPI STPv2 (System Trace Protocol). MIPI STP was developed as a generic base protocol that can be shared by multiple application-specific trace protocols. The new module can be used to decode a stream of STPv2 data. (PR #72151)
• Add a modem backend statistics module.
  Similar to how you can use kernel stats to e.g monitor how “high” your threads go, you can use this new module to keep an eye on buffer usage within the modem subsystem, and use the information to optimize their size. (PR #72576)

uart:~$ modem_stats buffer
ppp0_rx: used at most: 124 of 2048 (6%)
ppp0_tx: used at most: 2048 of 2048 (100%)
uart@b000_rx: used at most: 233 of 4096 (5%)
uart@b000_tx: used at most: 4062 of 4096 (99%)
cmux_rx: used at most: 124 of 2048 (6%)
cmux_tx: used at most: 2047 of 2048 (99%)
dlci_1_rx: used at most: 124 of 2048 (6%)
dlci_2_rx: used at most: 25 of 1024 (2%)

• Hierarchical state-machine operations in SMF (State Machine Framework) now follow a more “UML-like” transition flow. (PR #71729)
• New sys_bitarray_* APIs to now allow “popcount” (count how many bits are set), xor with another bitarray, as well as find the Nth bit set in a region. (PR #72901)
• New Kconfig, CONFIG_MEM_DOMAIN_ISOLATED_STACKS — on supported architectures, thread stacks within the same memory domains are now isolated, i.e. threads within the same memory domains have no access to others threads’ stacks.
• Added support for bt_disable in the ISO implementation. (PR #72690)
• west build now allows to pass the list of shield(s) you want to add to your board via the --shield argument — much more natural than the old way of passing -DSHIELD as a CMake parameter. (PR #72720)
• USB device “next” stack now has initial support for BOS (Binary Object Store). (PR #72215)

A big thank you to the 7 individuals who had their first pull request accepted this week, 💙 🙌: @alex-bellon, @charliegilliland, @luqasn, @roger1wang-intel, @nicogrx, @zaporozhets, and @srmnw.

As always, I very much welcome your thoughts and feedback in the comments below!

If you enjoyed this article, don’t forget to subscribe to this blog to be notified of upcoming publications! And of course, you can also always find me on Twitter and Mastodon.

Catch up on all previous issues of the Zephyr Weekly Update:

A very cool addition this week makes the lives of LLEXT extension developers easier, and makes me think I should already start working on some nice demos for when it will be time to announce Zephyr 3.7 (which is not until late July, though!). Check this out, alongside other cool news, in this new weekly update 🙂

Extension developer kit for LLEXT

Introduced with the latest Zephyr 3.6 release, the LLEXT (Linkable Loadable Extension) subsystem has been gaining a lot of traction lately.

In many cases, people developing the “core” of a Zephyr application designed to be extensible (e.g. a smart home gateway with a fancy display allowing for news “apps” to be added) are not the same people that will be developing the extensions (e.g. an energy monitoring or a weather forecast application, to take the previous example). LLEXT extensions as usually meant as lightweight “plugins” that use a well-controlled and limited set of APIs ; therefore, asking developers to setup a full-blown Zephyr development environment is overkill and error-prone.

This is where the new LLEXT Extension Developer Kit (EDK) comes in: it simplifies the development of extensions outside of the Zephyr tree, by allowing to generate an “SDK” (using west build -t llext-edk target) that packages all the necessary headers and compile flags relevant in the context of a given Zephyr app, effectively providing extension developers with all they need to start hacking away!

Try out the new EDK code sample and see PR #69831 for more details.

Sysbuild multi-target sample

As a way to make it easier to grasp the concepts behind sysbuild, and how it can be used to build multiple facets of your application at once (ex. the actual Zephyr application alongside an MCUboot bootloader), a new “multitarget Hello World” code sample has been introduced.

It showcases a classical Hello World application, except that it also includes the configuration files and explanation on how to build it and flash it for multiple targets (ex. different SoC cores), also leveraging the new hardware model and board target terminology in the process. (PR #69652)

Boards & SoCs

• New ARM architecture Kconfig options CONFIG_ROMSTART_REGION_ADDRESS and CONFIG_ROMSTART_REGION_SIZE allow to relocate the rom_start region (that typically contains the boot-vector data and irq vectors) to a custom region. (PR #71684)
• Removed limitation to 4 CPUs for SMP on x86, and also updated Zephyr kernel limitation to 32 CPUs (instead of 8) in the meantime! (PR #60230)
• Power management support added to Renesas SmartBond UART. (PR #62190)
• Power management support added to NXP RW61 SoC series. (PR #72758)
• Added USB support for NXP MCX N947. (PR #72386)
• Added RTC alarm support for all STM32 MCU series. (PR #71957)

New boards and shields:

• The STWIN.box (a.k.a. STEVAL-STWINBX1) from STMicroelectronics packs an impressive amount of sensors (accelerometer, magnetometers, MEMS microphones, …) and has Wi-Fi, Bluetooth, and NFC connectivity as well. It is now supported in Zephyr 🙂 (PR #72723)
• STM32H745I Discovery kit is a complete demonstration and development platform for STMicroelectronics Cortex-M4 and M7 based STM32H745XI MCU. (PR #72510)

Networking

• There is now a really great documentation page for the new HTTP server. It compliments the existing code sample quite well and really gives you all you need to know how to declare static resources, expose WebSocket endpoints, etc.
• A new net http shell command gives you the ability to get a quick snapshot of the HTTP resources currently available. (PR #72578)

Host:Port       Concurrent/Backlog        Resource type   Methods         Endpoint

192.0.2.1:80    1/10                      dynamic         GET,POST        /dynamic
                                          static          GET             /
                                          websocket       GET             /

1 service and 3 resources found.

• TLS sockets have been available and use in Zephyr for quite a while, so it was long time due that they’re no longer marked as “experimental)”. (PR #72482)

Drivers

• There were several improvements made to the LED strip driver class this week, including new API function to get the length of an LED strip at runtime, which is now also a mandatory binding property alongside color-ordering. (PR #71630)
• I2C driver for ESP32 now allows for clock speed to be configured at runtime. (PR #72380)
• Added support for GPIO for Apollo3 SoCs. (PR #72438)
• Added the ability to read the advanced capabilities (GETCAPS) of an I3C target. (PR #71792)
• Added DAC and ADC drivers for the General Analog Unit (GAU) peripheral as found on NXP RW SoCs. (PR #70506)
• New driver for Innovative Sensor Technology TSic xx6 temperature sensors. These are low-power, calibrated sensors with accuracy as high as ±0.07 °C at +20 °C. (PR#70432)
• Added support for DS18S20 High-Precision 1-Wire Digital Thermometer (maxim,ds18s20) to the existing DS18B20 driver. (PR #71286)

Bluetooth

• Bluetooth BAP (Basic Audio Profile) shell now supports receiving audio data from e.g. a PC over USB, and encoding it using LC3 before sending it. to BAP audio streams. (PR#71084)
• Added support for Hands-free Audio Gateway (AG), which can be enabled using CONFIG_BT_HFP_AG). The audio gateway profile allows the microphone/speakers of a Bluetooth device (ex. a computer) to be used as an audio input/output device for another Bluetooth device, such as a mobile phone. (PR #70532)
• Simplified Kconfig options and interface between the host and controller. (PR #72580)

Miscellaneous

• I think a lot of people don’t necessarily know it, but Zephyr has a complete State Machine Framework (SMF) that can greatly simplify the implementation of protocol stacks, graphical user interfaces, etc. There are a few places in Zephyr where SMF is being used, but until this week there was no dedicated sample showcasing SMF “on its own”. Thanks to an awesome contribution from Glenn Andrews, it’s not the case anymore, and I highly encourage you to check out this new sample! (PR #70921)
• A new build option, enabled via CONFIG_BUILD_OUTPUT_COMPRESS_DEBUG_SECTIONS, allows to compress debug sections and therefore reduce size of ELF files substantially. (PR #72436)
• As part of ongoing work to move away from TinyCrypt and towards PSA (#43712), MCUmgr switched to PSA for its crypto operations (ex. checksum and hash functions). (PR #71947)
• Added initial HID device support to the USB “next” stack. (PR #65801)
• Several welcome fixes and improvements were made to the scripts/footprint/size_report script. (PR #72316)
• When using deferred logging, new log_thread_trigger() API allows to essentially flush the log buffer by forcing the log thread to process any pending messages immediately. (PR #71530)
• nRF Services library is now available for the Nordic HAL. (PR #70245)

A big thank you to the 7 individuals who had their first pull request accepted this week, 💙 🙌: @trunghieulenxp, @jlh-makeen, @darkmoon32, @AyushKot96, @mstumpf585, @dapperlo, and @Rafal-Nordic.

As always, I very much welcome your thoughts and feedback in the comments below!

If you enjoyed this article, don’t forget to subscribe to this blog to be notified of upcoming publications! And of course, you can also always find me on Twitter and Mastodon.

Catch up on all previous issues of the Zephyr Weekly Update: