Onomondo SoftSIM documentation

These pages document nrf-softsim, the nRF91 integration. They cover what the code cannot tell you on its own: ordering constraints, hazards, and the reasons behind the design. For option-by-option detail, read Kconfig and lib/include/nrf_softsim.h — both are documented at the source.

Two codebases make up the SoftSIM:

Repository	Role
onomondo-uicc	The SIM. A portable, dependency-free C implementation of a SIM/UICC/USIM — APDU parser, smart-card filesystem, USIM authentication (MILENAGE), OTA remote file management. It knows nothing about Zephyr or Nordic hardware; it reaches the outside world through four port interfaces. Feature boundaries, specification coverage and host testing are documented in that repository.
nrf-softsim (this repository)	The nRF91 integration. A Zephyr module for the nRF Connect SDK that binds onomondo-uicc to the nRF91 modem, implements the port interfaces on Zephyr and TF-M, and ships a reference sample.

The nRF91 modem firmware supports a software SIM: instead of driving the physical SIM interface it forwards SIM requests (reset, APDUs) through the Modem library's SoftSIM interface to the application core, where this module answers them using onomondo-uicc. That interface was developed in partnership with Nordic Semiconductor.

┌───────────────────────────────────────────────────────────────────────┐
│ Your application                                        (Zephyr, NCS) │
├───────────────────────────────────────────────────────────────────────┤
│ nrf-softsim                                 Zephyr module (this repo) │
│   · modem glue, work queue                                            │
│   · ports: NVS fs + cache, PSA crypto, heap, logging                  │
├───────────────────────────────────────────────────────────────────────┤
│ onomondo-uicc                                       portable SIM core │
│   · APDU/TLV codecs, UICC filesystem, USIM auth (MILENAGE), OTA (RFM) │
├───────────────────────────────────────────────────────────────────────┤
│ nrf_modem SoftSIM interface                                 (nrfxlib) │
├───────────────────────────────────────────────────────────────────────┤
│ nRF91 modem core                                  (cellular protocol) │
└───────────────────────────────────────────────────────────────────────┘

nrf-softsim is consumed as a regular west module (zephyr/module.yml); its west.yml pins the nRF Connect SDK version the release is validated against. onomondo-uicc is vendored as a git submodule at lib/onomondo-uicc and built from source.

Pages

Page	What it covers
Architecture	Request lifecycle, threading, boot flow, the NVS-backed filesystem, the security model, the port and source maps.
Integration	Adding the module to your application, the options worth commenting on, flash partitioning, the filesystem template, resources and coexistence, adapting to your own board.
Provisioning	Profile format, delivery, the on-device flow, key storage, re-provisioning.

Just want it running? The top-level README is the quick path.

Supported hardware

nRF91 series (nRF9151, nRF9160, nRF9161) on the non-secure (*/ns) build targets — TF-M is required for key storage. Validated board overlays ship for the nRF9151 DK, nRF9160 DK, nRF9161 DK, Thingy:91 and Thingy:91 X.