v6.6.0 (Argon/Boron/B-SoM/B5-SoM/Tracker/Tracker-M/E-SoM-X/M-SoM/P2)

Device OS 6.6.0 Release is available in the Web IDE, Particle CLI and Workbench for (Argon/Boron/B-SoM/B5-SoM/Tracker/Tracker-M/E-SoM-X/M-SoM/P2).

Released on October 13th, 2026

See documentation about Device OS versions, their current state, upgrades and downgrades here.

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6.6.0

FEATURES

• [Cellular] eSIM-aware IDLE cellular state: with no enabled eSIM profile the modem stays on and reachable over AT but does not try to register #2953
• [system] Allow reading and clearing the last panic info over USB #2949

ENHANCEMENTS

• [Cellular] Registration backoff for deactivated SIMs: after the first hour of failed registration attempts, retries space out to 1/2/4 hours with the radio off #2959
• [Gen 4] RNG: switch to mbedTLS CTR_DRBG over an ADC-based entropy source #2950 #2965
• [system] Re-send the system describe when the ICCID changes (e.g. an eSIM profile switch) #2953
• [Gen 4] Backup RAM persists to the filesystem instead of a dedicated flash page #2948
• [build] Parallel build support (make -jXX) and ccache #2941
• [system] Non-blocking cloud handshake: the system loop keeps running while the DTLS and CoAP handshake is in progress #2937
• [Gen 4] Enable mbedTLS restartable ECP so handshake ECC operations don't block the system loop #2964
• [Gen 4] Speed up AES operations by moving AES tables from PSRAM into SRAM (MBEDTLS_AES_ROM_TABLES off) #2965
• Generate a heap panic if heap operation would cause a deadlock due to disabled scheduler #2944 #2958

BUGFIXES

• [Cellular] Detect and recover from an unresponsive modem AT interface while connected, reset connection state on every disconnect() exit path #2940
• [Cellular] [R510] Allow more time for the modem to answer AT after a parser error before hard resetting it #2940
• [Cellular] cellular_device_info() uses the cached info without taking the NCP client lock when the modem is off #2952
• [Cellular] [Quectel] APDU channel reliability fixes #2953
• [M SoM] Fix power leakage in STOP/ULP sleep mode (PB12/SWD_DATA pull-ups) #2936
• [Gen 3] usb: fix non-blocking Serial writes asserting on a full TX buffer and receiving with a null buffer #2939
• [Gen 3] [Gen 4] Fix malloc deadlocks when allocating with the scheduler suspended (SPI/I2C init, TCPServer constructor), __malloc_lock trylocks the mutex before panicking #2944 #2958
• [Gen 4] backup ram: initialize the retained system area on cold boot #2948
• [third_party] littlefs: fix truncate followed by a write tripping the pcache assert #2947
• [third_party] mbedtls: security fixes backported from 2.22.0 #2942
• [system] ledger: fix a HardFault on cloud disconnect during a ledger update, encode the result and error message in responses #2957
• [system] Disconnect from the cloud when the network interface carrying the cloud connection goes down and resume the session on reconnect; Cellular.disconnect() / WiFi.disconnect() on that interface now disconnect from the cloud first #2964
• [wiring] Fix SystemSleepConfiguration move assignment leaking wakeup sources (memory lost on every sleep cycle when reusing a configuration); fix network wakeup source/reason sizes and SystemSleepResult self-assignment #2968
• [wiring] pinAvailable() no longer initializes SPI; pins used by SPI/I2C/UART peripherals are detected from the pin function on Gen 3 and Gen 4 #2961
• [Gen 4] I2C: fix slave mode SCL hold and interrupt storm #2960
• [Cellular] [Quectel] EG91: recover from an unresponsive AT interface during PPP data dial #2962
• [Cellular] cellular_device_info() ignores and does not cache invalid ICCIDs, falls back to cached info if the modem query fails #2962
• [third_party] FreeRTOS: vEventGroupDelete() frees memory outside the scheduler-suspended section #2965

INTERNAL

• [build] Back-write the real module hash and CRC into the linked ELF files, so an ELF can be matched against the module hash a device reports #2949
• [Gen 3] Flash space savings: disable x509 certificate parsing on LOW_FLASH_SPACE platforms, compact USB string mapping table in USB driver #2954
• [Tracker] Stub out Wi-Fi code unused on scan-only platforms to save flash space #2954
• [Gen 3] NFC driver can be compiled out for debugging purposes #2953
• [ci] Faster CI builds #2941
• [test] Env var suite fixes: drop the empty env var set OTA workaround, make sure product level env vars are cleared #2943 #2955
• [hal] HAL_PLATFORM_STRICT_HEAP_LOCK_PANIC debug option to panic on any heap access while the scheduler is suspended #2963
• [ci] Don't ship test ELF files in CI release artifacts #2956
• [test] Sync the device public key before running tests, entropy source qualification test, EG91 PPP stall and power saving test reliability #2965 #2962 #2967

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System Binaries (all devices)

https://github.com/particle-iot/device-os/releases/download/v6.6.0/particle_device-os@6.6.0.zip