Sparkfun OLA logger serial issue

Trying to use the OLA board without IMU to log serial data from a board sending out 9600bps. About 50% of the time OLA gives me this message on the USB terminal on reset and sometimes while logging:

++ MbedOS Error Info ++

Error Status: 0x80FF0144 Code: 324 Module: 255

Error Message: Assertion failed: handle != NULL

Location: 0x49DBD

File: mbed-os/targets/TARGET_Ambiq_Micro/TARGET_Apollo3/device/serial_api.c+411

Error Value: 0x0

Current Thread: main Id: 0x10007E4C Entry: 0x4AF11 StackSize: 0x1000 StackMem: 0

x10006E28 SP: 0x1005FEEC

For more info, visit: … E_ARTEMIS_


– MbedOS Error Info –

The logger recovers after a few additional resets, but not consistent, sometimes it may recover after a single reset, sometimes it may take as many as 5. The logger works the other 50% or so times and without the serial connection attached works 100% with logging RTC data (no IMU) to files on SD card. Everything is 3.3V, 16GB SunDisk Ultra class 10 SD card. Pin 32 is activated to put OLA to sleep, that works, reset works to wake up the logger, but that is when I get the error above on wake from a reset and apparently when connected to serial data. OLA FW version is 2.4, units purchased on 2-14-24.

Any suggestions?


The baud rate and related configuration was not changed from the original setup as I wanted to test this logger with the minimum of changes to the config file. Also, about half the time, data are stored on the SD card, while the rest of time I get the error message. It definitely seems that this is somehow related to the serial connection, but the data are observed in parallel on a terminal program at 9600 baud so not sure why this logger is objecting to getting serial data consistently.

If there was a baud rate issue, I would not think that the logger would crash and stop logging altogether, I would think that it would just log garbage characters, like the terminal programs do when they interpret data at the wrong data speed.

Hi KPBio,

This sounds similar to this issue:

Please tell me more about your hardware:

What voltage level is your serial device using? It must be 3.3V for the OLA / Artemis. Are you using a MAX3232 chip to convert from RS232 to 3.3V?

Does your serial device keep transmitting data while the OLA is asleep?

Is the OLA providing power to the serial device? When the OLA is asleep, is the serial device powered off?

How ‘busy’ or ‘active’ is the serial device? Does it output data continuously? Or is it like a GPS / GNSS chip and only output data in bursts, once per second?

The issue could be something like:

The serial device TX pin is back-feeding power into the OLA RX pin, causing strange behaviour when the OLA wakes from sleep.

Or, perhaps the voltage levels are not correct?

Best wishes,


Hi KPBio,

I’ve been able to reproduce your issue, and I think I have a fix for it. Details are here: … 1976597458

More later,


Please try the v2.7 BETA firmware and let me know if it resolves your issue: … 1976662630

Best wishes,


HI Paul,

Yes, updating FW to v2.7 solved the OLA crashing problem with the serial data. Thanks for your quick response to this issue.

Excellent - thanks for the update. Glad that fixed your issue. I’ve just released v2.7 - but it is identical to v2.7_BETA, you don’t need to update again.

Best wishes,