Embedded C Developer – OpenSync/OpenWrt WiFi Router with Cellular Backup

Embedded C Developer – OpenSync/OpenWrt WiFi Router with Cellular Backup

Max Vendor Rate: $50

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