Embedded C Developer

Embedded C Developer – OpenSync/OpenWrt WiFi Router with Cellular Backup 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 Top Skills: Embedded C Development on Linux/OpenWrt: C programming, Linux internals, debugging, IPC, event-driven design OpenSync/OpenWrt Platform Development: OpenSync Managers, OVSDB, UCI, MQTT, OpenWrt build system Linux Networking & LTE/5G Cellular Integration: Routing, IPv4/IPv6, failover, QMI/MBIM, modem management, GRE/IPsec Additional Details: Team size 8 Direct report - None Key Deliverables: Apolis