Release-2025.07

RIOT-2025.07 "FieldGuide" - Release Notes

RIOT is a multi-threading operating system which enables soft real-time
capabilities and comes with support for a range of devices that are typically
found in the Internet of Things: 8-bit and 16-bit microcontrollers as well as
light-weight 32-bit processors.

RIOT is based on the following design principles: energy-efficiency, soft
real-time capabilities, small memory footprint, modularity, and uniform API
access, independent of the underlying hardware (with partial POSIX compliance).

RIOT is developed by an international open-source community which is
independent of specific vendors (e.g. similarly to the Linux community) and is
licensed with a non-viral copyleft license (LGPLv2.1), which allows indirect
business models around the free open-source software platform provided by RIOT.

About this release

The 2025.07 release puts documentation front and center. With our new and
shiny guide pages (#21404, #21436), it is easier than ever to pick up RIOT
and start hacking! The new guides are available on https://guide.riot-os.org/

Two new checksum calculations have been added to RIOT: CRC16/IBM-SDLC (#21552)
and reflected CRC8 with LSB first (#21543). The first one is needed for the
new Slipmux driver (#21418) that is also part of this release. The latter in
preparation for an upcoming 1-Wire driver (#19848).

This release includes the first part of the new Unified and Modular CoAP stack
(unicoap #21390), providing initial parser and message APIs.

One new MCU is available for RIOT: The ESP32-H2 (#21522), including support
for it's IEEE 802.15.4 capabilities (#21590).

RIOT continues the transition to #pragma once header guards and to the SPDX
license format (#21497, #21504, #21501, #21496, #21430, #21591, #21517).

132 pull requests, composed of 443 commits, have been merged since the
last release, and 3 issues have been solved. 29 people contributed with
code in 90 days. 3833 files have been touched with 77135 (+) insertions and
49624 deletions (-).

Notations used below

+ means new feature/item
* means modified feature/item
- means removed feature/item

New features and changes

Core

• core/thread_flags: add thread flags group (#21254)

• tree-wide: fix compilation with GCC 15.1 and picolibc 1.8.10 (#21443)

System Libraries

• checksum: Add crc16-fcs / IBM-SDLC (#21552)
• dist/tools/riotboot_gen_hdr: don't be pedantic, add
  riotboot_slot_get_current_hdr() (#21509)
• sys/atomic_utils: add bit set/clear helpers for unsigned int (#21440)
• sys/atomic_utils: add helpers for unsigned int (#21429)
• sys/bcd: add bcd_buf_to_u32() and bcd_buf_from_str() (#21428)
• sys/checksum: Add LSB-first (reflected) CRC8 Function (#21543)
• sys/stdio: add printf_long_long (#21445)
• sys/psa_crypto: Adding aead aes ccm (#21455)
• sys/psa_crypto: Adding ecc p256r1 pub key derivation (#21461)
• sys/ztimer: add support for timers running at a 500kHz frequency (#21553)

• sys/arduino: define LED_BUILTIN as frequently used by Arduino
  sketches (#21485)
• sys/event/deferred_callback: disable timer before modifying event (#21539)
• sys/event/thread: optimize stack usage (#21556)
• sys/event: make debug output of event_loop_debug more useful (#21456)
• sys/mineplex: Enhance Documentation (#21536)
• sys/psa_crypto: Rework Headers (#21512)
• sys/shell/cmd: typo in ifconfig helptext, 'transition' fixed as
  'transmission' (#21474)
• sys/shell: expose readline() (#21505)
• sys/shell: rename shell_readline() (#21506)
• treewide: migrate to XFA SHELL_COMMAND (#21514)

Networking

• gnrc/ipv6/nib: add option to disable router solicitations (#21437)
• net/unicoap: Unified and Modular CoAP stack: Parser and Message APIs
  (pt 1) (#21390)
• submac: add TX power to retrievable netopts (#21579)

• sys/net/sock_util: Do not depend on network stack (#21419)
• sys: replace header guards with #pragma once (#21497)

Packages

• pkg/mpaland-printf: Add alternative stdio as package (#20664)
• pkg/wakaama: add on off switch (#21109)

• pkg/driver_sx126x: bump to v2.3.2 (#21521)
• pkg: use esptool.py v4.9.0 as package (#21557)
• pkg/littlefs2: bump to 2.11.1 (#21583)
• pkg/littlefs2: bump version to v2.11.0 (#21491)
• pkg/nanopb: support more recent google.protobuf versions (#21587)

Boards

• boards/esp32s3-usb-otg: enable SDMMC peripheral (#21471)
• boards: add Wemos D1 R32 (aka ESPDuino-32) board definition (#21479)
• cpu/esp32: add ESP32-H2 support (#21522)
• features.yaml: add feather_shield feature (#21513)

• boards/adafruit-{clue,itsybitsy-nrf52}: Convert to Common adafruit- nrf52-bootloader module (#21395)
• boards/esp32: Arduino I/O mapping completion (#21484)
• boards/nucleo-l412kb: enable ADC (#21566)
• boards/nucleo-l432: enable ADC (#21546)
• boards: replace header guards with #pragma once (#21504)

CPU

• cpu/cortexm_common: add .backup.noinit section (#21559)
• cpu/esp32: add IEEE 802.15.4 support for ESP32-H2 (#21590)

• cpu/esp32: Migration to ESP-IDF v5.4 (#21261)
• cpu/sam0_common: enable static voltages (#21555)
• cpu/sam0_common: implement pm_off() (#14999)
• cpu/samd5x: improve isr buffer handling (#21486)
• cpu: replace header guards with #pragma once (#21501)
• periph_common/init.c: unblock i2c bus (#20787)

Device Drivers

• drivers/abp2: add abp2 driver (#20398)
• drivers/slipmux: Add to RIOT (#21418)
• drivers: add driver for MAX31865 resistance-to-digital converter (#21498)
• drivers: add MCP23x17 I/O expander support (#10688)

• drivers/netdev_ieee802154_submac: port to netdev_new_api (#20992)
• drivers: replace header guards with #pragma once (#21496)
• drivers/periph/gpio(_ll): Enhance and fix the documentation (#21538)
• pkg/driver_atwinc15x0: remove the compilation of the SPI Flash driver
  part (#21494)

Documentation

• doc/guide: Introduce a Guide Site (#21404)
• doc/guides: Add Getting Started guide (#21436)

• boards/avr: Update the link to the AVaRICE documentation (#21595)
• boards/nucleo-f031k6: improve board doc (#21581)
• boards/nucleo-f042k6: doc improvement (#21584)
• boards/nucleo-l412kb: improve board doc page (#21554)
• boards/nucleo-l432kc: improve board doc page (#21460)
• boards/nucleo: fix Cortex-M4F family in doc page (#21561)
• boards: rename doc.txt -> doc.md for particle, Microchip, nrf ...
  boards (#21596)
• cpu/esp*: migrate doc files to Markdown files *.md (#21589)
• doc/creating-an-app: clarify wording about Makefile.board.dep (#21493)
• doc/guides/general: switch out @ref usage (#21457)
• doc: move vision to starlight, deprecate vision in doxygen (#21576)
• sys/stdio: better document configuration (#21459)

Build System / Tooling

• tools: add default .clang-tidy configuration (#21431)
• dist/tools/riotboot_gen_hdr: add JSON mode (#21511)
• dist/tools: add a leading whitespace check for #pragma once in the
  headerguards static test (#21430)

• build system: improve cargo/docker interaction (#21465)
• build-sytem/openocd: detect serial port TTY (#21523)
• dist/tools/bmp: in-line dependencies using PEP 723 (#21131)
• dist/tools/compile_test: specify toolchain and exit code (#21534)
• dist/tools: bump uf2conv version (#21469)
• makefiles/defaultmodules*.mk: fix the description in comments (#21499)
• makefiles/docker: update riotbuild digest (#21542)

Examples

• Guides: Introduce C Tutorial (#21434)

• examples/basic/subfolders: switch from DIRS to EXTERNAL_MODULE_DIRS (#21476)
• examples/gnrc_lorawan: simplify configuration a bit (#21526)
• examples: move licenses from headers to SPDX format (#21591)
• examples: replace header guards with #pragma once (#21517)

Testing

• .github/workflows: Guide Site Build Test (#21458)
• tests/pkg/fatfs*: cleanup MTD default dependencies (#21478)

And 19 minor changes.

Deprecations

Bug fixes (22)

• drivers/sdmmc_sdhc: add timeout to wait for ISR mutex unlock (#21432)
• drivers/sx126x: add shield_sx1262 (#21441)
• tests/unittests: Add missing module dependency to enable UDP (#21597)
• boards/feather-m0: Correct ADC Settings (#21508)
• boards/nucleo-l432kc: fix typo in MCU table (#21550)
• boards/nucleo-l4: fix VBAT capable boards list (#21547)
• boards/seeedstudio-xiao-esp32c3: fix pin conflict (#21463)
• cpu/cc2538: Distinguish between GPIO_OD and GPIO_OD_PU (#21488)
• cpu/native: use correct isr_stack for valgrind (#21492)
• cpu/nrf5x_common: fix uart_poweroff() (#19926)
• cpu/nrf{52,9160}: set GPIO modes correctly for MISO/MOSI SPI signals (#21549)
• cpu/sam0_common: fix DAC on SAM D5x/E5x (#21548)
• doc/guides: fix examples directories (#21568)
• examples/basic/subfolders: fix test (#21480)
• guides: Fix link to docker setup (#21570)
• guides: use absolute path to fix url (#21571)
• Makefile.include: fix override headers from application (#20744)
• pkg/esptool: force installation of version 4.9.0 (#21588)
• pkg/lwip: fix dependencies when LWIP IPv4 is used (#21342)
• pkg/mpaland-printf: fix overriding printf with printf_float (#21439)
• sys/embunit: fix return value on failure (#21468)
• tests/drivers/{st77xx,ili9341}: fix coordinates in lcd_fill() (#21518)

Known issues

Network related issues (55)

• 6lo: RIOT does not receive packets from Linux when short_addr is set (#11033)
• Address registration handling inappropriate (#15867)
• app/netdev: application stops working after receiving frames with
  assertion or completely without error (#8271)
• at86rf2xx: Dead lock when sending while receiving (#8242)
• cpu/esp8266: Tracking open problems of esp_wifi netdev driver (#10861)
• DHCPv6 client: Handling of NotOnLink incorrect (#20349)
• dist/tools/sliptty/start_network.sh: IPv6 connectivity is broken on
  PC (#14689)
• driver/mrf24j40: blocks shell input with auto_init_gnrc_netif (#12943)
• drivers/at86rf215: Incorrect channel number set for subGHz (#15906)
• DTLS examples cannot send message to localhost (#14315)
• Emcute cannot create a double-byte name (#12642)
• ethernet: Missing multicast addr assignment (#13493)
• ethos: fails to respond to first message. (#11988)
• ethos: Unable to handle fragmented IPv6 packets from Linux kernel (#12264)
• example/gnrc_border_router cannot answer after some time (#19578)
• examples/cord_ep: Dead lock when (re-)registering in callback
  function (#12884)
• examples/gnrc_border_router: esp_wifi crashes on disconnect (#14679)
• Forwarding a packet back to its link layer source should not be
  allowed (#5051)
• gcoap example request on tap I/F fails with NIB issue (#8199)
• gcoap: Suspected crosstalk between requests (possible NULL call) (#14390)
• Global IPv6 addresses remain deprecated after receiving RA (#19846)
• gnrc ipv6: multicast packets are not dispatched to the upper layers (#5230)
• gnrc/ipv6: "invalid payload length" - corrupted IPv6 header when
  ENABLE_DEBUG=1 in mbox.c (#20390)
• gnrc_border_router stops routing after a while (#16398)
• gnrc_border_router: Kconfig and C disagree about number of addresses
  per interface (#19947)
• gnrc_icmpv6_echo: flood-pinging another node leads to leaks in own
  packet buffer (#12565)
• gnrc_ipv6: Multicast is not forwarded if routing node listens to the
  address (#4527)
• gnrc_netif_pktq leaks memory (#17924)
• gnrc_rpl: missing bounds checks in _parse_options (#16085)
• gnrc_rpl: nib route not updated when topology / DODAG changes (#17327)
• gnrc_rpl: old routes are not deleted (#19423)
• gnrc_rpl: takes unusually long time to start routing packets (#19147)
• gnrc_sock_udp: Possible Race condition on copy in application buffer (#10389)
• gnrc_tcp: gnrc_tcp_recv() never generates -ECONNABORTED (#17896)
• gomach: Resetting netif with cli doesn't return (#10370)
• ieee802154_submac: IPv6 fragmentation broken (#16998)
• LoRaWan node ISR stack overflowed (#14962)
• LWIP TCP Communication Error (#19676)
• lwip_sock_tcp / sock_async: received events before calling
  sock_accept() are lost due to race condition. (#16303)
• Missing drop implementations in netdev_driver_t::recv (#10410)
• Neighbor Discovery not working after router reboot when using SLAAC (#11038)
• netdev_ieee802154: Mismatch between radio ll address and in memory
  address (#10380)
• nrf52: Not able to add global or ULA address to interface (#13280)
• nrfmin: communication not possible after multicast ping with no
  interval (#11405)
• ping6 is failing when testing with cc2538dk (#13997)
• pkg/tinydtls: auxiliary data API does not work for async sockets (#16054)
• pkg/tinydtls: DTLS handshake does not work (#19595)
• Removing a TNT global address then adding a new one does not work (#20318)
• samr30 xpro doesn't seem to use its radio ok (#12761)
• scan-build errors found during 2019.07 testing (#11852)
• stale border router does not get replaced (#12210)
• test/lwip: enabling both, IPv4 and IPv6, results in unexpected
  behavior (#18097)
• tests/lwip: does not compile for IPv4 on 6LoWPAN-based boards. (#17162)
• two nodes livelock sending neighbor solicitations back and forth
  between each other (#16670)
• xbee: setting PAN ID sometimes fails (#10338)

Timer related issues (6)

• misc issues with tests/trickle (#9052)
• periph/timer: timer_set() underflow safety check (tracking issue) (#13072)
• periph_timer: systematic proportional error in timer_set (#10545)
• saml21 system time vs rtc (#10523)
• stm32_common/periph/rtc: current implementation broken/poor accuracy (#8746)
• sys/newlib: gettimeofday() returns time since boot, not current wall
  time. (#9187)

Drivers related issues (11)

• at86rf2xx: Simultaneous use of different transceiver types is not
  supported (#4876)
• cpu/msp430: GPIO driver doesn't work properly (#9419)
• examples/dtls-wolfssl not working on pba-d-01-kw2x (#13527)
• fail to send data to can bus (#12371)
• mdt_erase success, but vfs_format resets board (esp32-heltec-
  lora32-v2) (#14506)
• periph/spi: Switching between CPOL=0,1 problems on Kinetis with
  software CS (#6567)
• periph: GPIO drivers are not thread safe (#4866)
• PWM: Single-phase initialization creates flicker (#15121)
• STM32: SPI clock not returning to idle state and generating
  additional clock cycles (#11104)
• TCP client cannot send read only data (#16541)
• tests/periph_flashpage: unexpected behavior on nucleo-l4r5zi (#17599)

Native related issues (5)

• examples/micropython: floating point exception while testing on
  native (#15870)
• native not float safe (#495)
• native: tlsf: early malloc will lead to a crash (#5796)
• VFS_READ show correct data on every SECOND request only (#21470)
• ztimer doesn't wake up on native if the pm_layered module is used (#21083)

Other platforms related issues (14)

• Failing tests on FE310 (Hifive1b) (#13086)
• [TRACKING] Fixes for automatic tests of ESP32 boards. (#12763)
• boards/hifive1: flashing issue (#13104)
• cpu/sam0: flashpage write / read cycle produces different results
  depending on code layout in flash (#14929)
• esp32-wroom-32: tests/netstats_l2 failing sometimes (#14237)
• esp8266 crashes on WiFi disconnect (#21558)
• examples/gnrc_border_router: esp_wifi_init failed with return value
  257 on ESP32-C3 with nimble_rpble (#19319)
• gcoap/esp8266: Stack overflow with gcoap example (#13606)
• Interrupt callback function is instantly called on samd51 after
  setting it from within interrupt callback function (#19861)
• MPU doesn't work on cortex-m0+ (#14822)
• newlib-nano: Printf formatting does not work properly for some
  numeric types (#1891)
• periph_timer: Test coverage & broken on STM32F767ZI (#15072)
• riscv: ISR stack is too small for ENABLE_DEBUG in core files (#16395)
• stm32f7: Large performance difference between stm32f746 and stm32f767 (#14728)

Build system related issues (5)

• Build dependencies - processing order issues (#9913)
• dist/tools/cppcheck/cppchck.sh: errors when running with Cppcheck
  1.89 (#12771)
• EXTERNAL_MODULE_DIRS silently ignores non-existent entries (#17696)
• make: ccache leads to differing binaries (#14264)
• make: use of immediate value of variables before they have their
  final value (#8913)

Other issues (72)

• 2023.04 release bug tracking (#19469)
• [tracking] Bugs found by the peripheral selftest (#20071)
• [Tracking] Fix failures of test-on-iotlab (#20791)
• [TRACKING] sys/shell refactoring. (#12105)
• [tracking] unnecessary use of floating point arithmetic (#19614)
• _NVIC_SystemReset stuck in infinite loop when calling pm_reboot
  through shell after flashing with J-Link (#13044)
• make term no longer works with JLinkExe v6.94 (#16022)
• at86rf215 stops receiving until sending a packet (#19653)
• b-l072z-lrwan1: tests/ztimer_overhead: test failure (#19224)
• backport_pr: Only works for when fork is in user (not in
  organization) (#18486)
• benchmark_udp: hammering with low interval causes issues (#16808)
• boards/esp32-wroom-32: tests/mtd_raw flakey (#16130)
• Builds fail when different execstack options are around in objects (#18522)
• Can't build relic with benchmarks or tests (#12897)
• CC2538-CC2592EM has a very weak transmit power (#17543)
• CC2538DK board docs: broken links (#12889)
• cpp: Exception handling undefined (#17523)
• cpu/stm32: some tests are failing on CM33 (l5, u5) (#17439)
• doc/boards: information concerning access to RIOT shell (#17453)
• doc/doxygen: Broken LaTeX Formulas (#21490)
• doxygen: CSS hack to hide doc breaks on older browsers (#21312)
• edbg: long lines flooded over serial become garbled (#14548)
• examples / tests: LoRa tests fail on platforms that don't support
  LoRa (#14520)
• examples/gcoap: client broken (#19379)
• flashing issue on frdm-k64f (#15903)
• frdm-k22f failing tests/periph_flashpage (#17057)
• frdm-k22f fails tests/periph_timer (#19543)
• Freeze into semtech_loramac_send call (pkg/semtech-loramac) (#18790)
• gcoap: gcoap_req_send and related should return negative for errors (#19393)
• gnrc_ipv6_nib: Neighbor Solicitation ping-pong (#18164)
• I2C Crashes Kernel on Raspberry Pi Pico (#21187)
• I2C not working under RIOT with U8G2 pkg (#16381)
• ieee802154_security: Nonce is reused after reboot (#16844)
• kconfiglib.py choice override of menuconfig bug (#19069)
• lwip: drivers/at86rf2xx/at86rf2xx_netdev.c invalid state during TCP
  disconnect (#17209)
• lwip: invalid state transition on ieee802154_submac users (#17208)
• Making the newlib thread-safe (#4488)
• mcuboot: flashes but no output (#17524)
• MTD is confusing (#17663)
• Order of auto_init functions (#13541)
• periph_rtt: rtt_set_alarm() blocks IRQ for 80 plus usec on STM32 (#19520)
• pkg/tinydtls: Multiple issues (#16108)
• Potential race condition in compile_and_test_for_board.py (#12621)
• RIOT is saw-toothing in energy consumption (even when idling) (#5009)
• riotboot: ECC faults (eg. in STM32L5 or STM32WB) not handled
  gracefully (#17874)
• rpl, rpble: handle closed connection to parent(s) (#21574)
• rust-gcoap example is incompatible with littlefs2 (#17817)
• Samr30/gpio: Erasing then write mux can generate spurious IRQ (#19993)
• samr34-xpro: some tests failing (#19223)
• sock_dtls: unable to send big messages (#17996)
• spurious IRQs in periph_timer (#18976)
• stdio UART input truncated (#21564)
• stdio_ethos: infinite shell loop (#17972)
• stdio_tinyusb_cdc_acm hangs with picolibc (#19277)
• STM32 Nucleo boards improperly clocked (#19778)
• STM32F4-discovery + mrf24j40 not working (#19711)
• sys/riotboot: documentation issues (#11243)
• sys/usb/usbus/cdc/ecm: interface thread blocked when connected host
  interface is down (#21098)
• tests/lwip target board for python test is hardcoded to native (#6533)
• tests/periph_flashpage: failing on stm32l475ve (#17280)
• tests/pkg/lvgl: compilation error for BOARD=samr21-xpro (#21446)
• tests/pkg/relic is failing on samr21-xpro when built using llvm (#19903)
• tests/pkg_libhydrogen: test fails on master for the samr21-xpro with
  LLVM (#15066)
• tests/pkg_libschc: Failing test_reassemble_success_ack_always (#19445)
• tests/test_tools: test fails while testing on samr21-xpro/iotlab-m3 (#15888)
• tests: broken with stdio_rtt if auto_init is disabled (#13120)
• tests: some tests don't work with newlib lock functions. (#12732)
• Types in byteorder.h need a cleanup (#14737)
• USB identifiers with funny characters create mojibake (#17776)
• usbus/msc: wrong error handling and behavior after usb reset (#19478)
• Use of multiple CAN bus on compatible boards (#14801)
• ztimer is incompatible with real-time requirements (#18883)

There are 168 known issues in this release

Fixed Issues since the last release (2025.04)

• Missing _TARGETNAME variable in stm32wlx target config causes flash
  failure (#21614)
• sys/psa_crypto: one parenthesis too many in the documentation (#21563)
• RIOT OS webpage do not generate automatically from git repository (#21562)

3 fixed issues since last release (2025.04)

Acknowledgements

We would like to thank all companies that provided us with hardware for porting
and testing RIOT-OS. Further thanks go to companies and institutions that
directly sponsored development time. And finally, big thanks to all of you
contributing in so many different ways to make RIOT worthwhile!

More information

http://www.riot-os.org

Discussions

• Join the RIOT Matrix room at: #riot-os:matrix.org
• Join the RIOT Forum at: forum.riot-os.org
• Follow us on Mastodon: floss.social/@RIOT_OS

License

• The code developed by the RIOT community is licensed under the GNU Lesser
  General Public License (LGPL) version 2.1 as published by the Free Software
  Foundation.
• Some external sources and packages are published under a separate license.

All code files contain licensing information.