Embedded C Developer

Embedded C Developer/OpenSync/OpenWrt WiFi Router with Cellular Backup
Location: Onsite. Englewood, CO

JD:
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