IoT Zephyr

Zephyr Weekly Update – Participate in Zephyr Developer Survey 2023!

There is one week to go until the feature freeze for Zephyr 3.5, and also just about a week to participate in this year’s Zephyr Developer survey.

Whether you are using Zephyr for work or just for a pet project, we’d love to hear from you and understand what you love about the project and the community, and what you’d want to see improved. I promise it should take you less than 10 minutes to fill out, and your input will be incredibly useful to shape the future of the project.

Understanding and troubleshooting initialization levels

Understanding initialization levels and how all the various drivers “light up” when a Zephyr application starts can be pretty intimidating.

That’s why you will likely appreciate the introduction of a new tool making things very visual when it comes to the bootstrapping of your application.

The new initlevels target in west gives you a quick way to dump the list of init functions that are being called at each stage of the booting process. (PR #62459)

Let’s say I want to use this with the newly added LVGL demo apps, running on an M5Stack Core2.

 west build -t initlevels -p -b m5stack_core2 -s .\samples\modules\lvgl\demos\ --  -DCONFIG_LV_Z_DEMO_MUSIC=y

The output would be as follows, giving me a good overview of when each driver is kicking in, and making it easier to spot potential bugs in the bootstrap sequence of my application.

  __init___device_dts_ord_5: clock_control_esp32_init(__device_dts_ord_5)
  __init_statics_init_pre: statics_init(NULL)
  __init___device_dts_ord_11: gpio_esp32_init(__device_dts_ord_11)
  __init___device_dts_ord_13: gpio_esp32_init(__device_dts_ord_13)
  __init___device_dts_ord_58: entropy_esp32_init(__device_dts_ord_58)
  __init___device_dts_ord_61: uart_esp32_init(__device_dts_ord_61)
  __init_uart_console_init: uart_console_init(NULL)
  __init_sys_clock_driver_init: sys_clock_driver_init(NULL)
  __init_enable_logger: enable_logger(NULL)
  __init_enable_shell_uart: enable_shell_uart(NULL)
  __init_malloc_prepare: malloc_prepare(NULL)
  __init_k_sys_work_q_init: k_sys_work_q_init(NULL)
  __init___device_dts_ord_12: i2c_esp32_init(__device_dts_ord_12)
  __init___device_dts_ord_25: mfd_axp192_init(__device_dts_ord_25)
  __init___device_dts_ord_84: spi_esp32_init(__device_dts_ord_84)
  __init___device_dts_ord_80: regulator_axp192_init(__device_dts_ord_80)
  __init___device_dts_ord_81: regulator_axp192_init(__device_dts_ord_81)
  __init___device_dts_ord_82: regulator_axp192_init(__device_dts_ord_82)
  __init___device_dts_ord_85: regulator_axp192_init(__device_dts_ord_85)
  __init___device_dts_ord_26: gpio_axp192_init(__device_dts_ord_26)
  __init_gpio_hogs_init: gpio_hogs_init(NULL)
  __init___device_dts_ord_86: ili9xxx_init(__device_dts_ord_86)
  __init___device_dts_ord_14: ft5336_init(__device_dts_ord_14)
  __init___device_dts_ord_15: NULL(__device_dts_ord_15)
  __init_lvgl_init: lvgl_init(NULL)

Running LVGL demos is now (much) easier!

Thanks to Fabian’s excellent work in PR #62904, running one of the default LVGL ‘demo’ apps has become significantly easier this week.

Check out the instructions of the newly added code sample to get started in no time. It’s really exciting to see all the improvements being made around all things GUI recently!

By the way, in case you didn’t know, LVGL code can also run in an HTML canvas, which I find really cool.

Music Player App demo. More LVGL demos here.

Boards & SoCs

  • MPU/MMU-based stack guard is now enabled on ARM64. If you enable CONFIG_ARM64_STACK_PROTECTION, the system will trigger a fatal error if the current process stack overflows. This is done by preceding all stack areas with a fixed guard region. (PR #62902)
  • The Nuvoton NPCX7M6FB evaluation board is a development platform to for Nuvoton NPCX7 series of microcontrollers. It features an Arm Cortex-M4F MCU, with 256 KB RAM / 64 KB ROM — now supported! (PR #62799)


  • hwinfo driver is now available for TI SimpleLink CC13xx/CC26xx series. It allows to retrieve the device ID and to access the cause of reset. (PR #62537)
  • STMPE811 touch controller is now supported. (PR #61826)
  • RAM disk driver (which I didn’t know Zephyr had until today!) can now be easily configured directly via Devicetree. It now also supports multiple instances. (PR #60149)
/ {
	ramdisk0 {
		compatible = "zephyr,ram-disk";
		disk-name = "RAM";
		sector-size = <512>;
		sector-count = <192>;
  • The MCAN driver now supports statistics. It can be enabled using Kconfig CONFIG_CAN_STATS. (PR #62758)
  • New driver for NXP VREF. (PR #56822)
  • LTC2990 Quad I2C Voltage, Current and Temperature Monitor (no less!) from Analog Devices is now supported. (PR #60842)
  • On all STM32 ADC, it is no longer possible to read sensor channels (Vref, Vbat or temperature) using the ADC driver, and the dedicated sensor driver should be used instead. (PR #62345)
  • The driver for the LIS2DH accelerometer can now trigger an interrupt when a single tap is detected. (PR #62498)
  • Various improvements to the NVMe disk driver. (PR #62820)


  • When using the modem subsystem to describe “chat scripts” (ex. “If I send you this AT command, I’m interested in capturing this portion of your response”), you can now dynamically create chat scripts.
    This makes it possible to adapt to the runtime conditions, as the parameters of the various commands, or the expected responses, might not always be known at build time. (PR #62703)
    By the way, don’t forget to join us on Wednesday for our second episode of the Zephyr Tech Talks, as this will be your chance to learn more about the new modem subsystem from its author 🙂
  • A new lwm2m create shell command makes it easy to create and register new LWM2M objects on the fly. (PR #62869)
    Note to self: I need to prepare some demos around using LWM2M with Zephyr at some point 🙂
  • If you’re using the USB Device stack for building some kind of audio gadget, you can now expose volume control functionality to the host. (PR #60973)
  • SO_REUSEADDR and SO_REUSEPORT socket options are now supported, making it possible to have multiple sockets bound to the same local IP-port combination (PR #61885)
  • The shell commands settings read and settings write now accept an optional ‘type’ argument. Ex:
settings write string foo bar
settings write hex key2 c0ffee

A big thank you to the 9 individuals who had their first pull request accepted this week, 💙 🙌: @raitraak-rrk, @kapbh, @iandmorris, @gwa-storck, @kunoh, @icsys-aal, @aaronyegx, @SawXu, and @TaiJuWu.

As always, please feel free to jump in with your thoughts or questions in the comments below. See you next week!

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:

IoT Zephyr

Zephyr Weekly Update – Hello M5Stack Core2, Picolibc, et al.

This week, I am using the recently added support for M5Stack Core2 (thank you, Martin!) as an excuse to show you some pretty cool Zephyr tricks that I’m confident many of you didn’t know about 🙂

Before jumping right in, I want to say a big thank you to everyone who tuned in to the first Zephyr Tech Talk earlier this week. It was a lot of fun, there were tons of questions, and Mike was the perfect guest for this first episode.

On Wednesday, September 27, I will be chatting with Bjarki Arge Andreasen about the newly introduced modem subsystem, and I highly encourage you to sign up already to make sure you don’t miss this!

M5Stack Core2 is now supported, and why I find it extra cool

M5Stack Core2
M5Stack Core2
Did I mention the M5Stack Core2 is *packed* with on-board peripherals?

I am really excited that the support for M5Stack Core2 finally got merged this week. This is yet another great contribution from Martin Kiepfer and, similarly to the M5StickC Plus, I particularly like how this device is packed with on-board peripherals that happen to just work out-of-the-box in Zephyr.

I might record a longer demo video in the next few days, but in the meantime let me just show you three examples of why having out-of-the-box and full-blown support for the on-board peripherals is really neat:

  • The M5Stack Core2 features a power-management IC (PMIC), an AXP192, which is one of the supported regulators in Zephyr. It controls, among other things, the voltage being sent to the LCD backlight.
    Not sure what would be an appropriate brightness level for the LCD in your application? Curious about how low you can get until things are not really readable for your end-users anymore?
    Well, just use the built-in shell commands to interact with the regulator, and voila! No need to write custom test code and—maybe more importantly—no risk to fry your device since the min/max limits for all the power outputs are configured separately in the Devicetree.
uart:~$ regulator vget DCDC3
2.800 V
uart:~$ regulator vset DCDC3 2.5V
uart:~$ regulator vset DCDC3 3.3V
Why, yes, being able to interact with voltage regulators through shell commands is super convenient.
  • There is a real-time clock on board of the device (BM8563), connected to the main ESP32 over I2C.
    It’s of course a pretty useful companion for many applications where you need the date and. Again, not only is this particular RTC chip supported (so you can interact with it using the standard RTC API), but similarly to the regulator shell before you can, for example, easil set the date and time interactively, without having to write a single line of code for that.
uart:~$ rtc get pfc8563@51
uart:~$ rtc set pfc8563@51 2022-12-22
uart:~$ rtc get pfc8563@51
  • Last and certainly not least, the Core2 has an LCD display and a touch panel.
    I’ve mentioned it many times before but LVGL is an awesome tool for building embedded GUIs, and the fact that this particular device also has a touch interface makes it even more interesting, since LVGL input device interfaces and Zephyr’s input subsystem can work hand-in-hand. And as it seems to be all about shell awesomeness this week, here’s one more trick for you: the LVGL shell!
    It can be enabled using CONFIG_LV_Z_SHELL and it adds a couple commands that can be particularly useful for testing/troubleshooting your GUI. We all know that UI testing can be tricky, and even more so on embedded systems, and one such command allows you to enable an LVGL monkey which can be a great alternative to basically stress-test your UI and catch potential bugs, memory leaks, etc. Also, it’s super fun to watch, just see below!
uart:~$ lvgl monkey create pointer
Someone is really messing up with that touchscreen, eh? 🐵


This one is a pretty significant change! Picolibc is now the default C library for Zephyr.

Picolibc is a library offering standard C library APIs that targets small embedded systems with limited RAM.

In a nutshell, Picolibc brings even more modularity and configurability, making it easier to fine tune the footprint/performance of the C library. It’s also meant to bring you the best of both worlds between Zephyr’s minimal libc (small, but lacking too many features), and newlib (too heavy for most applications).

But frankly, I think I need to invite Keith, Picolibc’s author, to tell us more about it during an upcoming Zephyr Tech Talk (Keith, if you’re reading this… 😊).

You can of course still use CONFIG_LIBC_IMPLEMENTATION Kconfig to use another C library implementation.

Other boards & SoCs

Other boards added this week:

  • ESP32C3 LuatOS. Pretty nice to see more RISC-V boards, it had been a while! (PR #61915)
  • Raytac MDBT53-DB-40 and MDBT53V-DB-40 (PR #58841)


This week has been insane on the drivers front. Apologies if the list below is maybe not diving as deep as I typically try to into the specifics of each sensor as I usually do, but there’s just too much to cover this week. Hopefully the list below is a good and useful summary nevertheless.

  • Add support for devices of the ADC family MAX11102-MAX11117. (PR #60328)
  • TI TAS6422 is a two-channel audio amplifier for automotive applications (PR #59678)
  • TI BQ27z746 fuel gauge. (PR #59382)
  • TSL2540 ambient light sensor, a sensor that has, according to its datasheet, near photopic responsiveness (and yes, you too probably learned a word today!). (PR #59330)
  • When using RTC on STM32, it’s now possible to use calibration features (set_calibration / get_calibration), thanks to PR #62304, which also brings other fixes/improvements.
  • CAN-FD support has been added to ISO-TP, and the ISO-TP code sample has been updated accordingly. (PR #60323)
  • LPDAC (Low-Power Digital-to-Analogue Converter) support has been added for NXP LPCXpresso55S36. (PR #61459)
  • Native SD card support added for Microchip SAM4E MCU series (using ATMEL HSMCI peripheral). (PR #58233)
  • TI TCAN4x5x series of CAN controllers now supported, alongside the dedicated evaluation board, TCAN4550EVM. (PR #62033)
TCAN4550EVM (Credit: Texas Instruments)¶
  • Current sense amplifier driver, providing an easy way to describe a current sensing circuit hooked to an ADC, using some Devicetree magic, just see below. (PR #59139)
test_current: current_amp {
	status = "okay";
	compatible = "current-sense-amplifier";
	io-channels = <&my_adc_3>;
	io-channel-names = "CURRENT_AMP";
	sense-resistor-micro-ohms = <10>;
	sense-gain-mult = <1>;
	sense-gain-div = <1>;
  • It’s now possible to use NXP’s MU (Messaging Unit) as an MBOX device for inter-process communication.
  • Added support for Raspberry Pi Pico timer. (PR #57134)
  • KSCAN driver for Microchip now supports low-power mode. (PR #60806)
  • Driver for SSD1306 display now supports connections over SPI and I2C simultaneously. (PR #56887)
  • Driver for the BMM150 magnetometer now supports trigger mode. (PR #57985)


  • In addition to Bash and zsh, you can setup autocompletion for your West commands in fish shell. (PR #62477)
  • Added architectural support for shared interrupts. (PR #61422)
    I invite you to read this to learn more.
  • More LVGL goodness! PR #62141 introduces support for encoders as input devices. This can make for cool user interactions where you can e.g. use an encoder to focus on next/previous widget in the UI.
  • Wi-Fi shell keeps improving with PR #62201.

A big thank you to the 12 individuals who had their first pull request accepted this week, 💙 🙌: @electrocnic, @chuangzhu, @tswaehn, @andy3469, @likongintel, @Albort12138, @JPHutchins, @yclistanford, @vg-sc, @VivekUppunda, @wkhadgar, and @Emplis.

As always, please feel free to jump in with your thoughts or questions in the comments below. See you next week!

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:

IoT Zephyr

Zephyr Weekly Update – Charge me up!

Happy Friday! In case you missed it, yesterday I had the opportunity to join Robert and Michael from Arm (thanks again for the invitation, guys!) as part of their Innovation Coffee series. I forgot to actually bring some coffee, but we had a nice chat nevertheless, and you may want to catch up the recording.

Also on YouTube, and also live, don’t forget to join the first ever Zephyr Tech Talk next week next Wednesday, Sept. 13, at 1pm UTC.

And now for this week’s update…!

New battery charger subsystem

There’s been a lot happening recently in Zephyr around all things battery-powered, and this week a new subsystem has been introduced to help dealing with battery chargers.

Among other features, battery chargers play a crucial role in preventing your smartphone or other battery-powered devices from overheating and basically exploding during recharging. 🙂

They typically expose a range of properties that allow to get information about the battery (voltage, temperature, …), as well as settings that can be applied to e.g. limit the charging current (again, you don’t want that poor battery of your to explode!).

You can check out pull request #56666 for more context.

Boards & SoCs

  • Support has been added for Silicon Labs BRD4170A board. (PR #62145)
  • Texas Instruments SimpleLink CC13x2/CC26x2 family now support MCUboot out-of-the-box, as PR #62239 introduced the changes required to properly described the flash partitions it requires.
  • If you are a user of NXP RT1170, you can now use the LinkServer utility to flash your board. (PR #62229)


  • A driver has been added for the F75303 temperature sensor from Fintek. The sensor has three temperature channels in total: one local (on-chip), and two remote. (PR #60833)
    Something that’s pretty cool is that Pawel (a first-time contributor to Zephyr!) also added an emulator for the sensor! 🙌
  • The AD56xx series of DACs (Digital-to-Analogue Converters) from Analog Devices is now supported. (PR #60347)
  • New driver for Texas Instrument’s VIM (Vectored Interrupt Manager), which is an external interrupt controller used e.g. in Beaglebone AI64. (PR #60856)
  • PWM driver for STM32 now supports capturing on four channels. (PR #57607)
  • Power management support has been added to the very popular LM75 digital temperature sensor, so that reading from it properly fails when the sensor is not powered. (PR #61167)


  • Two significant improvements to I²C logging were introduced with PR #60301:

I²C log outputs are now better aligned to make them much easier to compare visually:

D: I2C msg: io_i2c_ctrl7_port0, addr=50
D:    W      len=01: 00
D:    R Sr P len=08:
D: contents:
D: 43 42 41 00 00 00 00 00 |CBA.....

You can now use the Devicetree to filter which subset of I²C communications you want to get logs for. Very smart and very cool!

/ {
    i2c {
        display0: some-display@a {
        sensor3: some-sensor@b {

    i2c-dump-allowlist {
        compatible = "zephyr,i2c-dump-allowlist";
        devices = < &display0 >, < &sensor3 >;
  • For maintainers and contributors, please be aware that a new extension to Zephyr’s documentation generation system (Sphinx) allows to document code samples more precisely, in particular by indicating which API they are a good sample for, so that they then show up nicely in the associated documentation. Of course, I encourage everyone to help with porting over existing code samples to the new system 🙂 (PR #62029)
.. zephyr:code-sample:: blinky
   :name: Blinky
   :relevant-api: gpio_interface

   Blink an LED forever using the GPIO API.
  • Sysbuild now allows to configure/build applications in a specific order. (PR #57884). Read more here.

A big thank you to the 11 individuals who had their first pull request accepted this week, 💙 🙌: @piotrnarajowski, @warrenb78, @chienhung-lin, @inteljiangwe1, @semihalf-anikiel-pawel, @semihalf-jakiela-albert, @RichardSWheatley, @rriveramcrus, @andrewmclachlanadi, @rtalbott-tmo, and @ihidchaos.

As always please feel free to jump in with your thoughts or questions in the comments below. See you next week!

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: