IoT Zephyr

Zephyr Weekly Update – Yes we CAN

As we’re entering a new month, I would like to start this week’s update with a quick look at some interesting metrics for the month of April, taken from the GitHub repository. And we are getting dangerously close to 500 boards supported upstream!

While I have your attention, I would also like to encourage you to take the Eclipse IoT Developer Survey and take some time to provide your input with regards to your embedded and IoT practices (which programming language or RTOS you use–hint, hint!–to hardware architectures, software supply chain management practices, etc).

And without further ado, let’s dive into this week’s noteworthy Zephyr contributions!

New boards, shields & SOCs

XMC4700 relax kit from Infineon.
  • XMC4700 relax kit board (#55435): Zephyr now supports the XMC4700 relax kit from Infineon. This evaluation board sports an XMC4700 micro-controller, based on an Arm Cortex-M4 @ 144MHz, with 2MB Flash and 352KB of RAM.
    This MCU is well-suited for applications that require motor control (ex: toys, power tools, industrial pumps, …) and for EV-charging scenarios.
  • ARC HS4xD support (#56683): Support for the ARC HS4x processor family has been added, including the board definition for the HS4xD development kit. Since some of you, just like me until a few weeks ago, might not be familiar with ARC processors, I recommend you have a look at the dedicated Wikipedia entry.
  • Many developer kits from ST Microelectronics feature a so-called Morpho connector. As opposed to the common “Arduino shield” type of connector, Morpho aims at exposing *all* the pins of the MCU, which can be really convenient to really make the most of the available peripherals.
    Thanks to Gerald and pull request #57468, ST Morpho connector nexus nodes are now supported and the pins mappings for Nucleo G431RB and Nucleo F302R8 boards have been contributed as examples.


  • NXP’s S32 family of microcontrollers are dedicated to automotive and industrial applications. As such, they support CAN XL, a variant of CAN that supports data rates up to 20MBit/s.
    With PR #52450, support has been added for NXP S32 CANEXCEL, and the board definition of the X-S32Z27X-DC has been updated accordingly.
  • The ADS114S08 from Texas Instruments is a low-power/low-noise 16-bit ADC. And of course, you’ve guessed correctly: it’s now supported 🙂 (#54911).
  • You might remember the Nordic nPM1300 Power Management Integrated Circuit (PMIC) from previous weeks, and the associated nPM1300-EK evaluation kit. PR #56929 added a driver for the charging module. The code sample for the evaluation kit has been updated accordingly.

Shell improvements

The Zephyr shell is definitely one of my favorite features. Its extensibility and ease-of-use to quickly expose “helpers” that help monitoring and troubleshooting an application are super convenient, and it’s great to see it got some love this week.

The Zephyr shell has been enhanced to allow capturing and retrieving return values from executed commands, making it easier for developers to diagnose issues and understand the outcomes of shell commands. Just use the retval command to get the return code of the command that was executed last.

uart:~$ sensor info
device name: [email protected], vendor: STMicroelectronics, model: hts221, friendly name: (null)
device name: [email protected], vendor: STMicroelectronics, model: lis2mdl, friendly name: (null)
device name: [email protected], vendor: STMicroelectronics, model: lps22hb-press, friendly name: (null)
device name: [email protected], vendor: STMicroelectronics, model: lsm6dsl, friendly name: (null)
uart:~$ helpp
helpp: command not found
uart:~$ retval

Debugging and Testing updates

  • As of version 0.12.0, OpenOCD supports Espressif’s USB JTAG Programmer. Therefore, there’s no need for a custom OpenOCD anymore if you want to debug for ESP-32. Very cool! The instructions for all the supported ESP32 devkits have been updated accordingly (#56935).
  • When using the flash simulator, ex. when targeting QEMU or native posix, one can now use a memory region as the storage area. This allows the flash simulator to keep its contents over a device reboot (#57380). See an example here.
  • Twister now (#57121) includes an option to shuffle tests across subsets, providing a more efficient and randomized testing environmentZephyr Weekly Update – May 5, 2023. This can help detect unwanted dependencies in test execution order, as well as distributing better tests among subsets (i.e. make sure tests that run longer are distributed more evenly).


  • New flags for disabling Neighbor Discovery/Multicast Listener Discovery per network interface (#57377): New network interface flags have been added to disable Neighbor Discovery (ND) and Multicast Listener Discovery (MLD) per network interface. This allows interfaces that do not support ND/MLD (like OpenThread) to coexist with other IPv6 interfaces.

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 the editions of the Zephyr Weekly Update:

IoT Zephyr

Getting Started with Zephyr RTOS on the MXChip IoT DevKit

As you may have read in the latest edition of my Zephyr Weekly Update, Zephyr RTOS now has support for the very popular MXChip AZ3166 IoT DevKit!

There are tons of IoT developer kits out there, but this one is particularly interesting to me as it’s been used by Microsoft for many years as one of the reference platform for the Azure IoT demos and tutorials. Many folks all around the world have had the opportunity to play with it, and I thought adding support for it in Zephyr RTOS would be a good opportunity to give everyone an excuse to learn more about Zephyr by directly getting their hands dirty.

I have just posted the following short video on my YouTube channel, and I encourage anyone interested in dusting off their MXChip DevKit to watch it and give the Zephyr Getting Started a try 🙂

Getting started with Zephyr RTOS on the MXChip IoT DevKit

If you have any questions or need help, feel free to leave a comment below or on the video!

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.

IoT Zephyr

Zephyr Weekly Update – I won’t retain you too long!

Welcome back to what I hope is starting to become part of a weekly routine for some of you. It certainly is for me 🙂 There are some very cool news this week, with the addition of a new retention mechanism, which I’ll explain in more details below.

I am also really excited to see that the popular AZ3166 MXChip IoT DevKit is now supported in Zephyr. It’s a developer kit that people familiar with Microsoft Azure IoT will certainly recognize, and I am looking forward to seeing what people will do with it now that it can be used with Zephyr!

Finally, a big shout-out to this week’s first time contributors: Andreas, Balthazar, Bill, Christian, Daniel, Katherine, Matthew, Sihyun, and Tarun.

New Retention Subsytem

The new retention system provides a robust and efficient way for applications to manage data that must be retained while the device is powered, without having to rely on non-volatile storage (64f4404).

The retention system API enables applications to read and write data to memory areas or devices that retain information while the device is powered. This functionality allows sharing information between different applications, or within a single application without losing state information upon device reboot.

Data Integrity

To ensure the validity of retained data, the retention system offers the option to use a magic header that can be used to verify if the front of the retained data memory section contains a specific value. An optional checksum of the stored data can also be appended to the end of the data, providing further validation.

Retained Data Partitioning

Data stored through the retention system can be partitioned into multiple distinct areas, making it easier to manipulate only the fields you need instead of a large binary blob.

There is extensive documentation about this new feature, so I definitely encourage you to check it out. Thanks Jamie for all the hard work on this!

New boards & shields

MXChip AZ3166 IoT DevKit
MXChip AZ3166 IoT DevKit
  • Like I mentioned in the intro, the MXChip AZ3166 IoT DevKit is now supported (ce339e3).
    It’s a board that many people familiar with the Microsoft Azure IoT ecosystem will not only recognize, but also likely already have somewhere in a drawer. If that sounds like you, I would definitely like to encourage you to give Zephyr a try, the Getting Started Guide is the best way.
    I am working on a short video that should make things even easier for you. Please let me know about your experience in the comments, if you give it a try!

    Note: the Wi-Fi module is not supported at this point, but contributions are welcome to propose an integration of the proprietary driver.
  • Adafruit’s Data Logger Shield is now supported (d4d8580). This shield provides an SD card slot and a real-time clock (RTC) for Arduino-compatible boards. The RTC chip it contains is the NXP PCF8523, for which a driver was contributed this week too.
  • Incremental ADC support (IADC) support has been added for Silicon Labs EFR32BG27 SoC (0417d38).
  • Added support for STM32U595 and STM32U599 with basic peripherals (a0ad7b7).


PAwR Advertiser and Sync Support

A typical application for BLE PAwR is electronic shelf labels (ESL)
A typical application for BLE PAwR is electronic shelf labels (ESL). Image credit: Dominic Alves.

The recently released Bluetooth 5.4 specification introduced the notion of Periodic Advertising with Responses (PAwR), a feature that allows Bluetooth Low Energy devices to perform energy-efficient, bi-directional, communication in a large-scale one-to-many topology. A typical application is electronic shelf labels (ESL).

As of this week, it’s now possible to use the PAwR Advertiser and Synchronization features (9021e2f, 95bc5cf). Support for Periodic Advertising Connection Procedure has also been added (PR 56374).

I encourage you to look at the codes samples (one for advertising, one for synchronizing, and the connection procedure too) to get more familiar with the functionality and how to use it in Zephyr.


  • A new driver for the Raspberry Pi Pico’s Programmable I/O (PIO) has been added (5abb1b1).
    PIOs can be used to implement custom peripheral interfaces or offload real-time tasks from the main processor. I like to think of it as a tiny FPGA that you can program using an assembly language, which describes the state machine dictating the behavior of your I/O pin. This, for example, would blink an LED attached to the pin:
.program hello
set pindirs, 1
  set pins, 1 [31]
  set pins, 0 [31]
  jmp loop

In order to illustrate how to use PIO for more complex/useful scenarios, a sample has been created that shows how to implement UART RX and UART TX pins over PIO. See example here, and driver here.

Vishay VEML7700 Ambient Light Sensor
  • The Vishay VEML7700 Ambient Light Sensor is a high accuracy ambient light sensor with an I²C interface (a665fc0). It has 16-bit of dynamic range and can perform ambient light detection from 0 to 120 klx.
  • New Incremental ADC (IADC) driver for SiLabs Gecko (0417d38). The incremental architecture uses oversampling to allow applications to trade speed for higher resolution (but it doesn’t look like oversampling is supported in the current implementation of the driver).
  • New driver for the NXP PCF8523 Real-Time Clock (RTC) (11fc5d0). The PCF8523 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption.
  • New driver for the Motorola MC146818B RTC (bfeb5043ac).
  • New Infineon CAT1 ADC driver (3e02d48e4e)
  • Texas Instruments INA3221 Current/Voltage Monitor (3746074). The INA3221 can sense current on up to 3 channels in a 0-26V range.

Updates to existing drivers

  • The SDHC driver has been updated to support different CPOL/CPHA SPI clock modes (1929eb3). This helps deal with SD Cards that require the clock to switch to low when not active.
  • The Semtech SX126x LoRa driver has been updated to support fine-grained Power Amplifier (PA) configuration for the STM32WL series (e78e8d7).
  • The hwinfo driver for all ESP32 boards has been updated to implement the get_reset_cause function (9eef799).

Miscellaneous Updates

  • Added Power Delivery (PD) Source Support to the USB-C Stack (see documentation).
  • A new MCUboot shell command (serial_recovery) has been added. It allows entering MCUboot’s serial recovery mode when the retention subsystem is used.
  • A new script has been added to generate coverage reports for the Zephyr’s BabbleSim-based tests (ad3c390).
  • New DT_ANY_INST_HAS_PROP_STATUS_OKAY macro. Given a Devicetree property name, it evaluates to 1 if any enabled instance of DT_DRV_COMPAT has the property or to zero if it hasn’t. (44ec128e8b)
  • To make first-time contributors feel welcome and encourage their continued involvement in the Zephyr project, a new GitHub action has been added that sends a greeting message to users when they open their first pull request or issue.
    I certainly encourage you to try it out by taking the plunge of doing your first contribution, if you’ve never contributed to the project!

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 the editions of the Zephyr Weekly Update:

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