Greetings From Cygnus Professionals Inc
Job Title: Embedded C Developer - OpenSync/OpenWrt WiFi Router with Cellular Backup
Location: Englewood, CO (Onsite/Hybrid as applicable)
Duration: Long Term Contract
Key Skills
- Embedded C Development
- OpenWrt
- OpenSync
- Linux Networking
- LTE/5G Cellular Integration
- OVSDB
- WiFi Router/CPE Development
- ARM/MIPS Linux Platforms
We're looking for an Embedded C Developer to work on next-generation residential gateway platforms that combine DOCSIS/fiber WAN connectivity with LTE/5G cellular backup. You'll be developing and maintaining firmware on OpenWrt-based hardware running the OpenSync framework, with direct impact on millions of deployed customer premises equipment (CPE).
Responsibilities
• Design, develop, and debug embedded C software for Linux-based residential gateway platforms (ARM/MIPS SoC)
• Develop and maintain OpenSync managers — event-driven daemons that interact with OVSDB for cloud-managed configuration and state reporting
• Implement and optimize LTE/5G cellular failover and fallback logic including modem management, route arbitration, and WAN healthchecks
• Develop LED state machine logic to provide accurate device status indication across complex multi-WAN scenarios
• Interface with cellular modems via AT commands, QMI/MBIM, USB, and PCIe (MHI) protocols
• Work with WiFi drivers (Qualcomm/Broadcom/Atheros) for 2.4GHz, 5GHz, and 6GHz radio configuration
• Debug kernel-level issues including PCIe enumeration, USB device management, network driver crashes, and kernel panics
• Implement and maintain secure communication channels using TLS with mutual authentication and tunneling protocols
• Analyze and resolve field issues using device logs, crash dumps, and remote diagnostics
• Develop init scripts, UCI configuration handlers, and persistent storage management for OpenWrt
• Write unit tests and participate in code reviews via GitLab merge requests
• Collaborate with hardware teams, QA, cloud platform engineers, and service provider partners
Required Skills
• 5+ years of embedded C development on Linux-based platforms
• Strong proficiency in C programming — pointers, memory management, IPC, event-driven architectures
• Experience with OpenWrt build system, package management, UCI configuration, and JFFS2/SquashFS overlay filesystems
• Familiarity with OpenSync or similar cloud-managed CPE frameworks (OVSDB, protobuf, MQTT telemetry)
• Experience with cellular modem integration — AT commands, QMI, network interface management (rmnet/wwan)
• Strong understanding of Linux networking — routing tables, metrics, netfilter, bridge interfaces, IPv4 and IPv6 dual-stack, neighbor discovery, DHCPv4/DHCPv6, SLAAC, and prefix delegation
• Understanding of TLS handshake with mutual authentication using X.509 certificates, certificate chain validation, and secure provisioning
• Knowledge of security and tunneling protocols — GRE tunneling, IPsec, VPN overlays, and secure encapsulation for cloud-managed traffic
• Experience with event loop frameworks (libev, libuv, or similar)
• Proficiency with debugging tools — GDB, strace, tcpdump, kernel logs, serial console
• Familiarity with Git, GitLab CI/CD, cross-compilation toolchains
• Understanding of WiFi standards (802.11ax/be) and wireless driver configuration
Preferred Skills
• Experience with Qualcomm IPQ series SoCs (IPQ5018, IPQ9574) and NSS/PPE data path
• Experience with Broadcom BCM series chipsets (BCM4908, BCM6750, BCM63178) and Memory Direct Engine (MDE) / hardware acceleration
• Knowledge of Atheros/QCA/BCM wireless chipsets and CFG80211/mac80211 driver architecture
• Knowledge of DOCSIS cable modem interaction and WAN interface management
• Experience with PCIe and USB subsystems in embedded Linux (device enumeration, power management, error recovery)
• Familiarity with eSIM/eUICC provisioning (LPA, GSMA SGP.22)
• Experience with carrier aggregation, NR5G NSA/SA, and multi-band cellular configurations
• Understanding of TR-069/TR-369 (USP) device management protocols
• Basic understanding of TR-181 data model for CPE device management and service configuration
• Experience with Kconfig-based build configuration
• Knowledge of flash storage considerations — wear leveling, persistent partitions, factory reset flows
• Familiarity with thermal management and power management (battery-powered CPE)
Tools & Technologies
• Languages: C, Shell scripting (sh/bash), Python (test automation)
• OS/Platform: OpenWrt (Linux 5.x/6.x kernel), ARM Cortex-A53/A73
• Frameworks: OpenSync, OVSDB, libev, protobuf-c, jansson (JSON)
• Chipsets: Qualcomm IPQ, Broadcom BCM, Atheros/QCA
• Networking: iproute2, iptables/nftables, ovsdb-server, hostapd/wpa_supplicant, GRE, IPsec
• Security: OpenSSL/mbedTLS, X.509 certificates, mTLS, certificate management
• Cellular: Qualcomm QCM/SDX modems, MHI, qcserial, AT+QENG/AT+COPS
• Protocols: IPv4, IPv6, DHCPv4/v6, DNS, MQTT, GRE, TLS 1.2/1.3
• Build: Make, Kconfig, OpenWrt feeds, cross-compilation (musl/glibc)
• Debug: GDB, valgrind, serial console, logpull analysis
• VCS/CI: Git, GitLab, merge request workflows
Nice to Have
• Experience working directly with ISP/MSO/OEM partners
• Exposure to hardware bring-up and board support package (BSP) development
• Experience with Agile/Scrum in a firmware development context
• Familiarity with SCTE/DOCSIS standards
• Understanding of TR-181 data model parameters for WAN management, WiFi configuration, and device monitoring
• Experience with GRE tunnel implementation for backhaul traffic in managed WiFi deployments
What You'll Work On
• Cellular failover/fallback state machines with sub-second transition handling
• LED indication logic for multi-WAN connectivity states
• Modem health monitoring and subsystem restart/recovery
• Internet reachability healthcheck frameworks
• Cloud-managed device configuration and telemetry reporting via MQTT
• Secure cloud connectivity using mTLS with X.509 certificate-based mutual authentication
• GRE tunnel management for cloud-redirected traffic
• Factory reset, firmware upgrade, and persistent storage management
• IPv4/IPv6 dual-stack network configuration, routing, and failover across DOCSIS and LTE interfaces
• WiFi radio configuration and performance optimization across Qualcomm / Broadcom platforms
• Kernel crash analysis and driver-level bug resolution
About Cygnus Professionals, Inc.
Cygnus is a Princeton, NJ-headquartered global Business IT consulting and software Services firm with offices in the USA and Asia. Cygnus offers and enables innovation and helps our clients accelerate time to market & grow their business. Over 15 years, we have taken great pride in continuing our deep relationships with our clients.
Cygnus Belief
We believe in our commitment to diversity & inclusion.
Equal Employment Opportunity Statement
Cygnus is an Equal Opportunity Employer. We ensure that no one should be discriminated against because of their differences, such as age, disability, ethnicity, gender, gender identity and expression, religion, or sexual orientation.
All our employment decisions are taken without looking into age, race, creed, color, religion, sex, nationality, disability status, sexual orientation, gender identity or expression, genetic information, marital status, citizenship status, or any other aspects of employment protected by federal, state, or local law. Applicants for employment in the US must have valid work authorization.
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