A
Embedded C Developer
Apolis
🇺🇸 United States
On-site
1 month ago
$40 – $45 / hour
- Embedded C
- Linux
- PCIe
- TLS
- GitLab
- Protocol Buffers
- MQTT
- IPSec
- Tcpdump
- Git
- GitLab CI/CD
- SoCs
- Bash
- Python
- Test Automation
- Cortex
- JSON
- IpTables
- mTLS
- DNS
- Agile
- Scrum
1 month ago
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
Embedded C Developer · Apolis