Modem crash with 0x4 while using DECT nr+ MAC/DLC APIs

[0x41]

Hi everyone,

I'm developing a star-topology network using DECT NR+ on nRF9161 DK nodes,
running modem firmware mfw-nr+_nrf91x1_2.0.0 (nRF Connect SDK 3.3.0).

My issue is a modem crash with error 0x4 on the FT side when it receives
a PDU of ~3200 bytes sent by the PT device via
nrf_modem_dect_dlc_data_tx(). After investigating the error code, I
increased the modem's shared memory using
CONFIG_NRF_MODEM_LIB_SHMEM_RX_SIZE, but the crash still occurs at this
payload size.

On the PT device side, the transmission itself doesn't seem to fail,
since the dlc_data_tx callback is called with status 0.

For clarification: the FT and PT nodes start exchanging data after
association. I haven't yet tried to reproduce the crash using the sample
application from [Hands on with DECT NR+ API release v2.0], and I also
wasn't able to capture a modem trace of the fault using the Modem
library.

Modem error: 0x4
PC: 0x561bc
SDK: 3.3.0

Sorry in advance if I've left out any details.

Kind regards,
Alessandro.

[Syed Maysum Abbas Zaidi]

Hi,

Yes , the error 0x4 is a modem-internal memory management fault, the modem runs out of internal memory during PDU reassembly on the FT side. One thing I would like to mention that the define NRF_MODEM_DECT_PHY_SHMEM_CTRL_SIZE was renamed to NRF_MODEM_DECT_SHMEM_CTRL_SIZE in 3.3.0. If your project still uses the old name, the control region size may get silently ignored so can you please look through all project files and if you find any old name then rename it to NRF_MODEM_DECT_SHMEM_CTRL_SIZE.

Moreover also ensure CONFIG_NRF_MODEM_LIB_SHMEM_CTRL_SIZE is set to at least 1832.

Best Regards,
Syed Maysum