Subsea production operator facing aging SEM electronics
A global oil and gas company operating advanced subsea production systems, where reliable communication and control are critical for safe and continuous operations in demanding underwater environments.
Obsolete microcontroller and modem on two SEM cards
As subsea systems age, maintaining their reliability becomes increasingly difficult due to component obsolescence, outdated architectures, and missing documentation.
The client faced this challenge across two critical SEM components: the Controller Card and the Communication Card.
The Controller Card required migration from an obsolete 16-bit microcontroller to a modern 32-bit architecture, while preserving system functionality and ensuring long-term component availability. At the same time, the Communication Card presented an even more complex issue, with missing documentation and source code for a legacy communication chip, making maintenance and future development highly uncertain.
Any upgrade needed to maintain compatibility with existing systems while ensuring reliability and readiness for future deployments.
Requirements for modernizing SEM controller and communication cards
To extend the lifecycle of the system, the solution needed to:
- replace obsolete components with long-term available alternatives
- migrate legacy software to modern architectures
- reconstruct missing knowledge through reverse engineering
- preserve existing system functionality and interfaces
- ensure compatibility with subsea operating conditions
- reduce future maintenance and development risks
The goal was to modernize critical modules without disrupting the broader system.
ARM Cortex migration and FPGA-based modem replication
A dual-track modernization approach was implemented, addressing both control and communication layers of the system. Instead of replacing entire modules, the focus was on upgrading key elements while maintaining compatibility with existing infrastructure.
For the Controller Card, software was migrated to a modern ARM Cortex-based architecture, with careful analysis to reuse existing code where possible and adapt it to the new platform. The work also included hardware design services focused on replacing obsolete components with modern equivalents selected for long-term availability while maintaining compatibility with the existing SEM architecture.
For the Communication Card, reverse engineering was used to reconstruct the functionality of a legacy communication chip with no available documentation. This functionality was then reimplemented on a modern FPGA platform, ensuring continuity of communication protocols and system behavior.
Technology stack:
- C/C++ for embedded software
- ARM Cortex M4 / Infineon XMC microcontrollers
- FPGA / PLD (Xilinx) for communication logic
- HDL (VHDL, Verilog, ABEL)
- Altium Designer / LTSpice for hardware design and simulation
- FMECA / Silicon Expert for reliability and lifecycle analysis
The project also highlights the importance of component selection, hardware-software integration, and backward compatibility, key considerations covered in our guide to embedded hardware design.
How the upgraded cards keep legacy interfaces and protocols
The upgraded Controller Card operates on a modern microcontroller architecture, delivering the same functionality as the original system while improving maintainability and future scalability.
The Communication Card replicates legacy modem behavior using FPGA-based logic, ensuring seamless communication with existing systems. By preserving interfaces and protocols, both modules integrate directly into the current subsea infrastructure without requiring structural changes.
Key capabilities:
- Migration from legacy 16-bit to modern 32-bit architecture
- Reverse engineering of undocumented communication components
- FPGA-based implementation of legacy communication logic
- Replacement of obsolete components with long-term alternatives
- Preservation of system functionality and interfaces
- Compatibility with harsh subsea environments
Continued subsea operation without a full SEM redesign
The modernization of both modules ensured continued operation of subsea systems without requiring costly and complex redesigns. By preserving compatibility with existing infrastructure, the solution minimized disruption while improving reliability and maintainability.
At the same time, the reconstruction of undocumented components reduced dependency on legacy knowledge, making future maintenance and development more predictable.
Results: longer SEM lifecycle and restored system knowledge
The solution delivered measurable improvements across key areas:
- Extended system lifecycle, delaying the need for replacement
- Reduced obsolescence risk, through modern component selection
- Avoided full system redesign costs, significantly lowering investment
- Improved reliability, in critical subsea operations
- Restored system knowledge, through reverse engineering
- Enabled future planning, with clearer technical foundations
The upgraded modules provide a stable foundation for future system evolution, allowing the client to plan further modernization efforts with reduced risk. The approach can be replicated across other legacy components, supporting long-term sustainability of subsea infrastructure.
Frequently asked questions
Can a legacy communication chip with no documentation or source code be replaced in a subsea SEM?
Yes, through reverse engineering and reimplementation on a modern FPGA. Reverse engineering reconstructs the chip's functionality, and FPGA-based logic then replicates the legacy modem behavior so communication protocols and system behavior stay unchanged. In this project, InTechHouse implemented the Communication Card logic on Xilinx FPGA / PLD hardware using VHDL, Verilog, and ABEL, which also restored system knowledge that had been missing.
How do you migrate SEM controller software from a 16-bit to a 32-bit microcontroller?
By analyzing the existing code, reusing it where possible, and adapting it to the new platform. Hardware work runs in parallel, replacing obsolete components with equivalents selected for long-term availability. In this project, InTechHouse migrated the SEM Controller Card software in C/C++ to an ARM Cortex-based architecture (ARM Cortex M4 / Infineon XMC), delivering the same functionality as the original system.
Which tools support reliability and lifecycle analysis when modernizing subsea SEM cards?
FMECA and Silicon Expert support reliability and lifecycle analysis during component selection. Component choices target long-term availability while preserving compatibility with the existing SEM architecture. In this project, InTechHouse used FMECA and Silicon Expert alongside Altium Designer and LTSpice for hardware design and simulation, so both upgraded SEM cards integrate into the current subsea infrastructure without structural changes.
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