Crazyflie 2.0 LPS25H I2C connection failure

[I3I-I]

Hi,

today I wanted to start up my crazyflie 2.0 again, after some time in the drawer, but I got the following console output:

SYS: ----------------------------

SYS: Crazyflie 2.0 is up and running!

SYS: Build 0:992fe7c2e9b0 (2026.04) CLEAN

SYS: I am 0x313438353133470600390036 and I have 1024KB of flash!

CFGBLK: v1, verification [OK]

DECK_DISCOVERY: Backend found: onewire

DECK_DISCOVERY: Backend found: deckctrl

DECK_CORE: 1 deck(s) found

DECK_CORE: Calling INIT on driver bcFlow for deck 0

PMW: Motion chip id: 0x49:0xB6

MPU9250 I2C connection [OK].

AK8963 I2C connection [OK].

LPS25H I2C connection [FAIL].

ESTIMATOR: Using Kalman (2) estimator

CONTROLLER: Using PID (1) controller

MTR-DRV: Using brushed motor driver

SYS: About to run tests in system.c.

EEPROM: I2C connection [OK].

STORAGE: Storage check [OK].

AK8963: Self test [OK].

SYS: stabilizer [FAIL]

DECK_CORE: Deck 0 test [OK].

Seems like the LPS25H has a problem. I read In the old forum, that it might be a soldering issue but I'm not sure which chip to resolder.

What are my other options? Can I send it somewhere for repairs?

Best regards
Benedikt

[stefanthorstenson]

Hi @I3I-I !

Thanks for reaching out! Yes, most likely the pressure sensor does not work.

Since you have a flow deck attached, the pressure sensor doesn't contribute to anything. An easy fix is to disable the LPS25H sensor in software, by commenting out row 56 in sensors_mpu9250_lps25h.c and recompile the software. This will make your Crazyflie disregard the LPS25H sensor; the self-test should pass and the stabilizer should work. Note that you will have to maintain your own "branch" since this means modifying the software.

We do not supply soldering support for this, I'm afraid. So if you want to work with a Crazyflie with all hardware working, I would recommend that you order a Crazyflie 2.1 PCB sparepart. I see you have a Crazyflie 2.0. The 2.1 version will work off the shelf with your other parts, and is also slightly improved.

Let me know how it goes!

Best regards,
Stefan

[I3I-I]

Hi Stefan,

thanks for your swift response!

Alright! Disabling will be option, but I think I will try to resolder the LPS25H first myself. If that fails, I got a fallback with your workaround.

Unfortunately ordering a spare at this price tag is not an option, since it is just a little hobby sideproject of mine. Maybe it is, after I grilled the pcb :-D

Best regards,
Benedikt

[stefanthorstenson]

I see! Sounds fun!

Just to clarify, by "no soldering support" I mean, you cannot send your PCB to us for repairs. But let us know if you need any support here on Github, we might be able to help you!

Good luck and happy soldering :)

[I3I-I]

Hi @stefanthorstenson,
I managed to successfully resolder the lps25h. My crazyflie 2.0 now starts up and shows a plausible altitude value, but does blink red continuously. Not sure if this is normal behaviour.

Furthermore, I get a warning, that my stabilizier loop rate is off.

These are the logs I captured - one with and one without flow deck:

SYS: ----------------------------
SYS: Crazyflie 2.0 is up and running!
SYS: Build 0:992fe7c2e9b0 (2026.04) CLEAN
390036 and I have 1024KB of flash!
CFGBLK: v1, verification [OK]
DECK_DISCOVERY: Backend found: onewire
DECK_DISCOVERY: Backend found: deckctrl
DECK_CORE: 1 deck(s) found
PMW: Motion chip id: 0x49:0xB6
MPU9250 I2C connection [OK].
AK8963 I2C connection [OK].
LPS25H I2C connection [OK].
ESTIMATOR: Using Kalman (2) estimator
CONTROLLER: Using PID (1) controller
MTR-DRV: Using brushed motor driver
SYS: About to run tests in system.c.
EEPROM: I2C connection [OK].
STORAGE: Storage check [OK].
AK8963: Self test [OK].
DECK_CORE: Deck 0 test [OK].
SYS: Self test passed!
STAB: Wait for sensor calibration...
SYS: Free heap: 14368 bytes
STAB: Starting stabilizer loop
ESTKALMAN: State out of bounds, resetting
STAB: WARNING: stabilizer loop rate is off (950)
SYS: ----------------------------
SYS: Crazyflie 2.0 is up and running!
SYS: Build 0:992fe7c2e9b0 (2026.04) CLEAN
SYS: I am 0x313438353133470600390036 and I have 1024KB of flash!
CFGBLK: v1, verification [OK]
DECK_DISCOVERY: Backend found: onewire
DECK_DISCOVERY: Backend found: deckctrl
DECK_CORE: 0 deck(s) found
MPU9250 I2C connection [OK].
AK8963 I2C connection [OK].
LPS25H I2C connection [OK].
ESTIMATOR: Using Complementary (1) estimator
CONTROLLER: Using PID (1) controller
MTR-DRV: Using brushed motor driver
SYS: About to run tests in system.c.
EEPROM: I2C connection [OK].
STORAGE: Storage check [OK].
AK8963: Self test [OK].
SYS: Self test passed!
STAB: Wait for sensor calibration...
SYS: Free heap: 17256 bytes
STAB: Starting stabilizer loop
STAB: WARNING: stabilizer loop rate is off (899)

Do you have a hint, what is going on here?

Best regards,
Benedikt

[ArisMorgens]

Hello @I3I-I!

Based on your console output, it seems that the LPS25H is now properly connected - nice work!

When properly initialized, the Crazyflie should blink its red M1LED approximately 2 times per second. Is this what you mean by blinking red continuously? You can find more information on the led indications here.

Regarding the stabilizer loop rate, it's probably due to Crazyflie 2.0's structure. I get the same warning on a platform I flashed with the latest firmware. I think you can ignore it for now.

[I3I-I]

Thanks!

Yes M1 blinks with approximately 2Hz, so this should be fine.

Ok, thanks for clarifying!