RIOT-2022.04 - 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 2022.04 release includes the following new features and improvements:

Core:

The scheduler allows for changing the priority of a thread at runtime.

System libraries:

The module ztimer64_xtimer_compat was added, providing the complete xtimer
API on top of ztimer64_usec. This is now the default implementation when using
the xtimer module.
Most modules use ztimer instead of xtimer now.

The sequence of modules during auto initialization can be customized via
statically assigned numbers now. This feature is experimental, so use it with
caution. Priorities may change in the future.

SenML implementation: supports CBOR encoding, Phydat to SenML encoding and
basic SAUL integration.

Various improvements have been made to the file system modules:
VFS supports automatic mount (and formatting) at startup and reliable disk
enumeration, and mount_by_path. Default mount points can be provided by the
board configuration. exFAT support was added to FATFS.

Using Rust in RIOT no longer requires a nightly version of Rust, but can be
built on the latest stable on Rust instead.

Boards:

Boards no longer have to provide a board_init() function. LEDs are
initialized automatically if they follow the LED<x>_PIN naming scheme.

Networking:

gcoap now provides a simple forward-proxy and allows for switching between
plain CoAP and CoAP-over-DTLS at runtime.

The NimBLE module supports the new PHY modes that have been introduced with
Bluetooth 5.

A Telnet server module is available now.

Packages:

The build system now allows for package directories to reside outside the RIOT
tree.

Various new packages have been added:

the C++ Embedded Template Library (ETL)
nanors, a tiny, performant implementation of reed solomon codes
tflite-micro as a replacement for tensorflow-lite
WAMR adds Web assembly (WASM) support

Hardware support:

New support for the boards Adafruit-PyBadge and STM32 Nucleo-F439ZI as well as
for the LPS22CH nano pressure sensor and MCP47xx DAC. The DOSE bus now supports
baud rates of 1 MHz and above.

Summary:

328 pull requests, composed of 810 commits, have been merged since the
last release, and 6 issues have been solved. 40 people contributed with
code in 83 days. 1851 files have been touched with 50235 (+) insertions and
18701 deletions (-).

Notations used below

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

New features and changes

Core

core/sched: add sched_change_priority() (#17093)
core: add functionality to check queue state of another thread (#16174)

core: split out library code (#17652)
core/rmutex: use atomic utils (#16919)

System Libraries

drivers: migrate xtimer64 and xtimer/ticks users to ztimer (#17367)

drivers/mtd_flashpage: add mtd_flashpage_t type (#17627)
sys/bitfield: add support for bit-wise bitfield operations (#17710)
sys/senml: add SenML modules (#16384)
sys/vfs: add vfs_mount_by_path() (#17661)
sys/xtimer: introduce xtimer_is_set() (#17630)
sys/ztimer: add ztimer64_xtimer_compat complete xtimer replace module (#17670)
vfs: Introduce reliable disk enumeration (#17660)

rust: test on stable (#17805)
sc_vfs: print file size (#17622)
sys/auto_init: custom auto-initialization sequence (simple) (#17794)
sys/event/timeout: remove alternative xtimer implementation (#17689)
sys/evtimer: remove deprecated evtimer_now_min (#17655)
sys/fido2: use ztimer instead of xtimer (#17753)
sys/posix/pthread: newlib compatibility (#17734)
sys/test_utils/print_stack_usage: work with small stacks (#17891)

sys/vfs: add file-system auto-mount (#17341)

sys/vfs: provide vfs_fsync() (#17621)
sys/xtimer: make xtimer_ztimer_compat default backend (#17721)
sys/ztimer doc: List prerequisites for successful use of ztimer_now (#17614)
sys/ztimer64/util.c: fix ztimer64_set_timeout_flag (#17561)

sys/ztimer: add auto_adjust module (#17633)

sys/ztimer: cleanup xtimer_compat.h for 32Bit only (#17690)
sys/ztimer: Name callback types (#17758)
sys: some simple xtimer->ztimer conversions (#17892)
sys/*timer: rework dependencies to ease backend switch, prefer
ztimer_xtimer_compat over xtimer_on_ztimer (#17811)
sys/syscalls: make gettimeofday() implementation optional (#17733)
sys/ztimer: auto-select ztimer_no_periph_rtt only for samd21 (#17786)
sys: sort out ztimer_xtimer_compat and ztimer64_xtimer_compat depes (#17732)

tests: add stack usage metrics (#17706)

{examples,tests}/rust: Rust updates (-sys/-wrappers version, stable) (#17761)

Networking

gcoap: add simple forward-proxy (#13790)
gnrc_pktbuf_cmd: add od dependency with gnrc_pktbuf_static (#17228)
nanocoap: add nanocoap_get_blockwise_url_to_buf() function (#17833)
nanocoap: introduce coap_opt_remove() (#17881)
nimble/netif: add support for BT5 PHY modes (#16860)
sys,examples,tests,fuzzing: add missing includes (#17714)
sys/net/application_layer/sock_dns: add pseudomodule
auto_init_sock_dns (#17493)
sys/net/application_layer/sock_dns_mock: add module for mocking
sock_dns (#17871)
sys/net/application_layer: add telnet server module & example (#16723)
sys/net/dsm: add missing dependencies (#17685)
sys/net/nanocoap: introduce nanocoap_sock_*(), use in
suit/transport/coap (#17474)
sys/net/netutils: add netutils_get_ipv4() (#17764)
sys/net/sock: add sock_udp_sendv() API (#17485)
sys/net/sock_util: add sock_tl_name2ep() to optionally perform DNS
lookups (#17510)
sys/stdio_nimble: add new stdio module using nimble (#12012)

drivers/encx24j600: define default parameters (#17747)
gcoap: multi-transport support (#16688)
gnrc/ipv6nib: remove the need for evtimer-minutes (#17411)
gnrc/netif: convert to ztimer (#17354)
ipv6/nib: bugfix of 6CO length checking (#17850)
ipv6/nib: fix memcpy() bug in _handle_rtr_timeout() (#17741)
lwip: enable LWIP_SO_RCVTIMEO if sock layer is used (#17779)
pkg/lwip: use ztimer_msec instead of xtimer (#17115)
pm: don't (un)block IDLE mode (#17975)
sys/gnrc/sixlowpan/frag/fb: guard sfr_types.h header include (#17730)
sys/net/gnrc/sock: use ztimer_usec or xtimer for timeout (#17852)
sys/net/gnrc/sock_types: guard tcp.h header inclusion (#17743)
sys/net/gnrc: ztimer_no_periph_rtt if gomach (#17729)
sys/net/gnrc_sixlowpan_frag_sfr: use xtimer_set (#17668)
sys/net/link_layer/csma_sender: use public xtimer_now() (#17731)
sys/net/sock_util: fix compilation for IPv4-only mode (#17766)

Packages

buildsystem: add EXTERNAL_PKG_DIRS functionality (#17211)
pkg/etl: Add the embedded template library (etl) (#17477)
pkg/lvgl: add extra widget dependency (#17760)
pkg/nanors: add reed solomon codec implementation (#17703)
pkg/tflite-micro: add support and deprecate tensorflow-lite (#17908)
pkg/tinydtls: add IPv4 support (#17765)
pkg/uwb-dw1000: add patch for rf_txctrl value (#17724)
pkg/wamr: add WAMR to provide WASM support in RIOT (#15329)

buildsystem/pkg: expand packages from USEPKG early as path into
PKG_PATHS (#17551)
make: pkg.mk: don't call git am if there are no patches (#17858)
pkg/edhoc-c: bump version (#17777)

pkg/fatfs: fatfs_vfs: wire up format() (#14430)

pkg/fatfs: enable exFAT support (#17798)
pkg/fatfs: implement statvfs() (#17634)
pkg/littlefs2: bump version to 2.4.2 (#17837)
pkg/lv_drivers: initial commit (#17713)
pkg/lvgl: bump to 8.2.0 (#17681)
pkg/lvlgl: allow cusomizing LV_MEM_SIZE (#17759)

pkg/mbedtls: initial pkg import to use entropy module (#15671)

pkg/mynewt-core: fix semaphore (#17771)
pkg/semtech-loramac: enable setting channels mask (#17824)
pkg/tinycbor: bump version (#17604)
pkg/tinydtls/sock_dtls: use ztimer_usec (#17677)
pkg/tinydtls: migrate to ztimer64_msec (#17564)

Boards

boards/adafruit-pybadge: add support (#17807)
boards/b-l475e-iot01a: Add SPI2 and SPI3 buses (#17885)
boards/nucleo-f429zi: add support for ethernet (#17828)
boards: add support for nucleo-f439zi (#17827)
cpu/esp32: update to Espressif's precompiled ESP32 vendor toolchain
with gcc 8.4.0 (#17769)
cpu/stm32: add backup battery monitoring (VBAT) (#16989)
sys/auto_init: add auto_init_leds, drop LED init code from boards (#17584)
sys/board_common: add generic board_init() function (#17008)
sys/vfs: add vfs_default, configure default fs for same54-xpro (#17643)
tests/external-boards: add esp compile test boards (#17525)
vfs_default: add compile test and add default mount for more boards (#17656)

boards/native: select MTD defaults for FAT (#17653)
boards/nucleo-f334r8 f429zi and f446ze: enable cpy2remed programmer (#17708)
boards/nucleo-f767zi: fix adc_config indentation (#17682)
boards/same54-xpro: support for board variation with SST26VF064B
flash (#17613)
boards/stm32mp157c-dk2: Overwrite mpu_stack_guard in kconfig (#17629)
boards: drop board_init() from board.h (#17707)
boards: fix ztimer adjust values for arduino-mega2560 and z1 (#17839)
drivers/ft5x06: allow multiple device types (#17540)
kconfig explore all allowed boards on all apps (#17595)

CPU

cpu/native/netdev_tap: Add to netdev_register (#17635)
cpu/nrf52-9160: add periph_spi_init_gpio (#17617)
cpu/riscv_common: Enable Rust applications (#17520)
cpu/sam0_common: add periph_spi_init_gpio (#17616)
cpu/stm32: Add STM32_LINE cases for STM32L1xxx6 (#17727)
cpu: add flash_writable section to linker script (#17436)

cpu/arm7, arch/cortexm: Remove -fno-builtin flag (#17898)
cpu/cc2538/rtt: fix rtt_set_counter (#17535)
cpu/efm32: bump Gecko SDK version (#17672)
cpu/esp*: nvs-flash / cpp dependencies cleanup (#17548)
cpu/esp32/esp-eth: move GNRC auto_init to init_devs (#17745)
cpu/esp32: changes for toolchain update to gcc version 8.4.0 (#17546)
cpu/esp32: download Espressif SDK ESP-IDF as package (#17455)
cpu/esp32: enable puf_sram feature (#17671)
cpu/esp32: use macros/units (#16341)
cpu/lpc23xx-mci: migrate to ztimer_msec (#17363)
cpu/riscv_common: enable puf_sram feature (#17665)
cpu/riscv_common: fix undeclared memory region linker error (#17581)
cpu/sam0_common: implement EXTWAKE for SAM L21 (#17687)
cpu/sam0_eth: implement SLEEP state (#17886)
cpu/samd5x: allow to block IDLE mode (#17883)
cpu/saml21: derive low power SRAM length from model number (#17686)
cpu/samx21: allow to override PM_BLOCKER_INITIAL (#17793)
cpu/samd51: allow to support ADC0 and ADC1 in the same configuration (#17819)
cpu/stm32/i2c: fix wrong speed parameters (#17324)
cpu/stm32: Fix clock tree (#17609)
cpu/stm32: Fix CLOCK_CORECLOCK on stm32l0/l1 (#17725)
cpu/stm32: make backup SRAM available (#16870)
drivers/periph_spi: spi_init_with_gpio_mode mode by reference (#17531)

Device Drivers

driver/lpsxxx: adding lps22ch support (#17697)
drivers/dose: introduce watchdog timer (#17180)

drivers/dose: make use of ringbuffer for RX (#17210)

drivers/mtd_spi_nor: add ztimer_usec alternative (#17836)
drivers/shtcx: converted the shtc1 driver into shtcx and added shtc3
support (#17699)
drivers: add driver for L3GD20H 3-axis gyroscope (#10082)
drivers: support for Microchip MCP47xx DAC devices added (#10518)
mtd doc: Add overview defining terms; link modules (#17666)

driver/mtd_spi_nor: cleanup sleep timing (#17879)
drivers/dose: migrate to ztimer_usec (#17565)
drivers/lis2dh12: use ifdef instead of IS_USED (#17563)
drivers/mtd_sdcard: support unaligned reads & writes (#17619)
drivers/periph_common/cpuid: disable false positive warnings (#17910)
drivers/rtt_rtc: select rtc_utils (#17530)
drivers/sht3x: ztimer_msec port (#17783)

Documentation

boards/cc1352-launchpad doc: adding information concerning shell
access (#17522)
doc/doxygen: add BUILD_IN_DOCKER extended doc (#17820)
doc/doxygen: recommend adding ADJUST ztimer values for new boards (#17846)
doc: add RIOT root doxygen example path (#17572)
net/ieee802154: Add overview documentation (#16940)

boards/nucleo-f429zi: improvements to documentation (#17875)
boards/nucleo-l552ze-q doc: Improvements to documentation (#17639)
boards/p-nucleo-wb55: update documentation (#17582)
core (largely doc): Differentiate message types from thread flags (#17472)
doc/emulator: update qemu doc with unix sockets (#17751)
doc: small fix of "Getting Started" document structure in section
docker (#17756)
doc: Start documenting pseudomodules (#17133)
tools/zep_dispatch: document topogen usage (#17586)

Build System / Tooling

dist/tools/genconfig: add error on hidden symbols (#17597)
dist/tools/usb-serial/ttys.py: Add regex support (#17876)
dist/tools/usb_serial: Add tool for listing and filtering TTY
interfaces (#17737)
make: Add ubsan support (#17278)
makefiles/dependency_resolution: add outer loop for DEFAULT_MODULE
deps (#17632)
makefiles/docker.inc.mk: add DOCKER_ENV_VARS_ALWAYS (#17396)
testbed/iotlab: add mapping for samr34-xpro and nucleo-wl55jc (#17578)
tests/gnrc_rpl: add automated test for gnrc_rpl (#17353)
tools/pr_check: add "Update" keyword to "needs squashing" check (#17822)

make/emulate: use unix sockets with qemu (#17679)
Makefile.include: pass IOTLAB_NODE to docker (#17545)
makefiles/docker.ink.mk: do not always pass CFLAGS to docker (#17818)
makefiles/libc/newlibc: allow toolchains with nano version only (#17553)
makefiles: socat set tty mode 8N1 (#17853)
makefiles: use C++14 standard by default for C++ compilations (#17479)
tools/dhcpv6-pd_ia: create /run/kea on startup (#17674)
tools/cpy2remed: Addition of new programmer for nucleo boards (#17550)

Kconfig

boards/Kconfig: remove wrongfully added MODULE_AUTO_INIT_LED* sym (#17684)
cpu/stm32: Add clock config for mp1 to kconfig (#17521)

board/*/kconfig: Fix boards on kconfig blocklist (#17467)
boards: Use BOARD.config pattern for kconfig (#17648)
cpu/stm32/wl: Model kconfig clocks (#17496)
drivers/*/Kconfig: Cleanup of simple drivers (#17669)
pkg/littlefs2: model Kconfig (#17882)
sys/chunked_ringbuffer: model Kconfig (#17744)
sys/fido2: model Kconfig (#17435)
{disp,touch}_dev: improve Kconfig at different levels (#17458)

Examples

examples/gcoap_block_server: add gcoap block server example (#17843)
examples/lorawan: add the possibility to use ABP activation procedure (#11237)

examples/gcoap_dtls: match Makefile of examples/gcoap (#17552)
examples/twr_aloha: refactor (#17406)
examples/twr_aloha: blacklist test on ci (#17557)
Make example/emcute_mqtt honor radio settings (#17773)

Testing

.github/workflows/test-on-iotlab: add dwm1001 (#17558)
tests/*: add BOARDs to Makefile.ci (#17754)
tests: add default BOARDS (#17715)

CI: disable microbit testing (#17953)
murdock: prioritize job collection over build jobs (#17610)
murdock: support emulated boards (#17434)
murdock: use json output $(BINDIR) size (#17213)
tests/*: remove unneeded xtimer_init (#17566)
tests/xtimer: remove unneeded timex calls (#17728)
tests/driver_dfplayer: use event_thread instead of
event_thread_lowest (#17750)
tests/periph_uart_nonblocking: migrate to ztimer (#17567)
tests/pkg_edhoc: handle multiple interfaces (#17534)
tests/pkg_mbedtls: improve entropy test case and doc (#17606)
tests/pkg_relic: increase stacksize (#17528)
tests/senml: do no include saul_default (#17641)
tests/sys_atomic_utils: use ztimer_usec (#17851)
tests/sys_crypto: fix potentially uninitialized error (#17718)
tests/thread_float: use ztimer_usec (#17835)
tests: multiple fixes (#17840)
workflow/tool-test: update prior install (#17738)

API Changes

drivers/periph_common: add periph_init_buttons to init on-board
buttons (#17711)

drivers/atwinc15x0: register with netdev (#17887)
sys/pm_layered: use array representation, get rid of implicit IDLE
mode (#17895)
tests: rework eth drivers (#17813)
ztimer_periodic: make callback function return bool (#17351), i.e., the logic
of the return value is inverted now (ZTIMER_PERIODIC_KEEP_GOING was 0, now it
is true).

And 57 minor changes.

Deprecations

Deprecations (3)

sys/quad_math: this module has been marked as deprecated and will be removed
for the next release

sys/sema: add sema_ztimer64 to implement old api, deprecate sema (#17719)

periph/flashpage: deprecate *_free functions (#17860)

Removals (3)

drivers/at: remove deprecated AT_SEND_ECHO define (#17500)
sys/lora: remove deprecated LORA_PAYLOAD_CRC_ON_DEFAULT define (#17517)
sys/loramac: remove deprecated LORAMAC_DEFAULT_PUBLIC_NETWORK (#17516)

Bug fixes (39)

make: add -ffunction-sections -fdata-sections to LINKFLAGS if LTO=1 (#16789)
pkg/openwsn: add patch to use memmove() instead of memcpy() (#17900)
[treewide] lora: use int16_t for RSSI value (#17497)
boards/common/qn908x: perform elf checksum on shadow copy (#17757)
boards/nucleo-f767zi: Fix adc pin config in periph_conf.h (#17560)
core/assert: avoid including panic.h with assert.h (#17574)
cpu/native: fix build with afl-gcc 11.2 (#17583)
cpu/nrf52 radio: Populate info (#17592)
cpu/nrf52/radio: fix confirm_op info cast (#17848)
cpu/sam0_common/eth: expose correct setup function (#17746)
dist/tools/kconfiglib: avoid rewriting /dev/null (#17873)
drivers/at86rf215: fix disabling individual modulations (#17667)
drivers/atwinc15x0: join multicast groups (#17880)
drivers/dose: only disable watchdog when transiting from RECV state (#17716)
drivers/ethos: fix build without ethos_stdio (#17608)
drivers/mtd_mapper: fix read_page and write_page backend (#17866)
examples/lorawan: disable loramac state persistence on EEPROM
(#17970)
fs/constfs: omit leading '/' in readdir() (#17626)
gnrc/ndp: bugfix set O-flag if target is not anycast (#17778)
gnrc/nib: don't advertise single address for auto-configuration (#17803)
gnrc_netif: fix potential null pointer dereference (#17856)
makefiles.kconfig.mk: use EXTERNAL_MODULE_DIRS in Kconfig resolution (#17596)
murdock: fix exit -> return in subfunction (#17518)
pba-d-01-kw2x: fix clock init by preceding cpu_init with modem clock
init (#17857)
pkg/fatfs: fix missing mutex header (#17865)
pkg/littlefs*: align readdir() with documentation (#17623)
pkg/tinydtls/contrib/sock_dtls: fix ep_to_session (#17849)
pkg/tinydtls: crypto: remove unnecessary usage of malloc() (#17878)
pkg: fix documentation on includes (#17538)
shell/sc_gnrc_udp: always use delay in µs (#17657)
sys/benchmark: fix divide by zero if runs < 1000 (#17624)
sys/event/callback: in init set list_node.next to NULL (#17625)
sys/fido2/ctap: fix parsing validation (#17816)
sys/net/dhcpv6: miscellaneous tweaks (#17736)
sys/ztimer/xtimer_compat: fix bug introduced in #17690 (#17705)
sys/ztimer64: fix ztimer64_remove() not properly clearing timer
struct (#17720)
tests/cpu_avr8_xmega_driver: fix BOARD name (#17749)
treewide: initialize several stack-allocated, but uninitialized timer
structs (#17855)
vfs: Initialize stat buffers so FSs don't have to (#17645)

Known issues

Network related issues (56)

6lo gnrc fragmentation expects driver to block on TX (#7474)
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)
at86rf2xx: lost interrupts (#5486)
CC2538 RF overlapping PIN usage (#8779)
core: "Invalid read of size 4" (#7199)
cpu/esp8266: Tracking open problems of esp_wifi netdev driver (#10861)
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 choose global source address. (#13745)
ethos: Unable to handle fragmented IPv6 packets from Linux kernel (#12264)
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)
General 802.15.4/CC2538 RF driver dislikes fast ACKs (#7304)
gnrc ipv6: multicast packets are not dispatched to the upper layers (#5230)
gnrc_border_router stops routing after a while (#16398)
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_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_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)
net: netdev_driver_t::send() doc unclear (#10969)
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)
openthread: does not build on current Arch (#10809)
ping6 is failing when testing with cc2538dk (#13997)
pkg/tinydtls: auxiliary data API does not work for async sockets (#16054)
Possible memory leak in RIOT/build/pkg/ndn-riot/app.c (#15638)
Riot-os freezes with lwip + enc28j60 + stm32L4 (#13088)
samr30 xpro doesn't seem to use its radio ok (#12761)
scan-build errors found during 2019.07 testing (#11852)
send data with UDP at 10HZ, the program die (#11860)
stale border router does not get replaced (#12210)
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)
Unclear how Router Solicitations are (or should be) handled (#15926)
xbee: setting PAN ID sometimes fails (#10338)

Timer related issues (15)

cpu/native: timer interrupt issue (#6442)
misc issues with tests/trickle (#9052)
MSP430: periph_timer clock config wrong (#8251)
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)
Sleep mode for Arduino (#13321)
stm32_common/periph/rtc: current implementation broken/poor accuracy (#8746)
sys/newlib: gettimeofday() returns time since boot, not current wall
time. (#9187)
tests: xtimer_drift gets stuck on native (#6052)
xtimer mis-scaling with long sleep times (#9049)
xtimer: add's items to the wrong list if the timer overflows between
_xtimer_now() and irq_disable() (#7114)
xtimer_set_msg: crash when using same message for 2 timers (#10510)
xtimer_usleep stuck for small values (#7347)
xtimer_usleep wrong delay time (#10073)

Drivers related issues (18)

(almost solved) SPI SD-Card driver: SPI initialisation freeze until
timeout (#14439)
adc is not a ADC-Driver but a analog pin abstraction (#14424)
at86rf2xx: Simultaneous use of different transceiver types is not
supported (#4876)
cpu/msp430: GPIO driver doesn't work properly (#9419)
driver/hts221: Temperature and Humidity readings incorrect (#12445)
ESP32 + DHT + SAUL reading two endpoints causes freeze. (#12057)
examples/dtls-wolfssl not working on pba-d-01-kw2x (#13527)
fail to send data to can bus (#12371)
floats and doubles being used all over the place. (#12045)
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)
Potential security and safety race conditions on attached devices (#13444)
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)
Two bugs may lead to NULL dereference. (#15006)

Native related issues (6)

examples/ccn-lite: floating point exception while testing on native (#15878)
examples/micropython: floating point exception while testing on
native (#15870)
native getchar is blocking RIOT (#16834)
native not float safe (#495)
native: tlsf: early malloc will lead to a crash (#5796)
SIGFPE on native architecture when printing double floats on Ubuntu
21.04 (#16282)

Other platforms related issues (21)

Failing tests on FE310 (Hifive1b) (#13086)
[TRACKING] Fixes for automatic tests of ESP32 boards. (#12763)
arm7: printf() with float/double not working (#11885)
boards/hifive1: flashing issue (#13104)
Cannot use LLVM with Cortex-M boards (#13390)
cpu/cortexm_common: irq_enable returns the current state of
interrupts (not previous) (#10076)
cpu/sam0: flashpage write / read cycle produces different results
depending on code layout in flash (#14929)
cpu/stm32f1: CPU hangs after wake-up from STOP power mode (#13918)
esp32-wroom-32: tests/netstats_l2 failing sometimes (#14237)
esp8266 precompiled bootloaders don't support partitions past 1MB (#16402)
gcoap/esp8266: Stack overflow with gcoap example (#13606)
I found stm32 DMA periph driver bugs! when I tested stm32l431rc
board. (#16242)
Incorrect default $PORT building for esp32-wroom-32 on macOS (#10258)
MIPS: toolchain objcopy doesn't work and no .bin can be generated (#14410)
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)
stm32152re: hardfault when DBGMCU_CR_DBG* bits are set and branch
after __WFI() (#14015)
stm32f7: Large performance difference between stm32f746 and stm32f767 (#14728)
sys/riotboot/flashwrite: unaligned write when skipping
RIOTBOOT_MAGIC on stm32wb (#15917)

Build system related issues (13)

buildtest uses wrong build directory (#9742)
make -j flash fails due to missing make dependencies or make flash-only rebuilds the .elf (#16385)
Build dependencies - processing order issues (#9913)
build: info-build doesn't work with boards without port set (#15185)
BUILD_IN_DOCKER ignores USEMODULE (#14504)
dist/tools/cppcheck/cppchck.sh: errors when running with Cppcheck
1.89 (#12771)
doxygen: riot.css modified by 'make doc' (#8122)
macros: RIOT_FILE_RELATIVE printing wrong file name for headers (#4053)
make: ccache leads to differing binaries (#14264)
make: Setting constants on compile time doesn't really set them
everywhere (#3256)
make: use of immediate value of variables before they have their
final value (#8913)
Tracking: remove harmful use of export in make and immediate
evaluation (#10850)
Windows AVR Mega development makefile Error (#6120)

Other issues (56)

semtech_loramac_init blocking (#17907)
[TRACKING] sys/shell refactoring. (#12105)
_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)
make term output is inconsistent between boards, ethos and
native (#12108)
assert: c99 static_assert macro doesn't function for multiple
static_asserts in the same scope (#9371)
Basic test for periph/rtt introduced in #15431 is incorrect (#15940)
boards/esp32-wroom-32: tests/mtd_raw flakey (#16130)
boards/saml11-xpro: second UART is broken (#17206)
Bug: openocd 0.10.0-6 Ubuntu dies while debugging with -rtos auto (#13285)
C++11 extensions in header files (#5561)
Can't build relic with benchmarks or tests (#12897)
CC2538DK board docs: broken links (#12889)
cpu/stm32/periph/rtc overflow error (#16574)
cpu/stm32: some tests are failing on CM33 (l5, u5) (#17439)
doc/LOSTANDFOUND: not rendered as expected (#17063)
edbg: long lines flooded over serial become garbled (#14548)
examples / tests: LoRa tests fail on platforms that don't support
LoRa (#14520)
feather-m0: make flash reports "device unsupported" (#17722)
flashing issue on frdm-k64f (#15903)
frdm-k22f failing tests/periph_flashpage (#17057)
I2C not working under RIOT with U8G2 pkg (#16381)
ieee802154_security: Nonce is reused after reboot (#16844)
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)
nanocoap: incomplete response to /.well-known/core request (#10731)
newlib-nano: Printf formatting does not work properly with "PRIu8" (#17083)
Order of auto_init functions (#13541)
pkg/tinydtls: Multiple issues (#16108)
Possible memset optimized out in crypto code (#10751)
Potential race condition in compile_and_test_for_board.py (#12621)
pyterm on stdio_cdc_acm stops working after a few seconds (#16077)
RIOT cannot compile with the latest version of macOS (10.14) and
Xcode 10 (#10121)
RIOT is saw-toothing in energy consumption (even when idling) (#5009)
riotboot/nrf52840dk: flashing slot1 with JLINK fails (#14576)
riotboot: ECC faults (eg. in STM32L5 or STM32WB) not handled
gracefully (#17874)
rust-gcoap example is incompatible with littlefs2 (#17817)
scheduler: priority inversion problem (#7365)
stdio_ethos: infinite shell loop (#17972)
sys/fmt: Missing tests for fmt_float, fmt_lpad (#7220)
sys/riotboot: documentation issues (#11243)
sys/stdio_uart: dropped data when received at once (#10639)
tests/cpp11_*: failing on i-nucleo-lrwan1 (#14578)
tests/lwip target board for python test is hardcoded to native (#6533)
tests/periph_flashpage: failing on stm32l475ve (#17280)
tests/pkg_libhydrogen: test fails on master for the samr21-xpro with
LLVM (#15066)
tests/pkg_tensorflow-lite: tests randomly failing on nrf52dk and
esp32-wroom-32 (#13133)
tests/test_tools: test fails while testing on samr21-xpro/iotlab-m3 (#15888)
tests/thread_float: crashes on avr-rss2 (#16908)
tests: broken with stdio_rtt if auto_init is disabled (#13120)
tests: some tests don't work with newlib lock functions. (#12732)
Tracker: Reduce scope on unintended COMMON variables (#2346)
usb-serial/list-ttys.sh: Broken when a debugger offers multiple
serial ports (#15814)
Use of multiple CAN bus on compatible boards (#14801)

There are 185 known issues in this release

Fixed Issues since the last release (2022.01)

Kconfig: genconfig.py rewrites /dev/null (#17862)
gcoap_dtls: Selecting transport at run time is not possible (#16674)
LTO broken (binaries too large) (#16202)
File systems report names with leading slashes (#14635)

4 fixed issues since last release (2022.01)

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

Matrix and Forum

Join the RIOT Matrix room at: #riot-os:matrix.org
Join the RIOT Forum at: forum.riot-os.org

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.

Release-2022.04