OpenSync/OpenWrt Embedded C Engineer - LTE/5G Failover

Themesoft Inc.; Englewood (CO); On-site; USD 100,000 - 140,000; Full time

Job summary

The Embedded C Developer role at Themesoft Inc. focuses on building and maintaining OpenWrt-based gateways with OpenSync, enabling LTE/5G cellular backup and multi‑WAN resiliency. You will work on OpenWrt firmware, OVSDB-based cloud configuration, and secure, scalable device management.

Ideal candidates have strong C expertise on Linux, hands-on OpenWrt/OpenSync experience, and a track record with cellular modems, WiFi drivers, and kernel debugging. Onsite Englewood, CO welcomed.

Qualifications

• 5+ years of embedded C development on Linux-based platforms.
• Experience with OpenWrt build system, UCI, 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, IPv4/IPv6, DHCPv4/DHCPv6, and related protocols.
• TLS mutual authentication, X.509 certificates, and secure provisioning concepts.
• Knowledge of security and tunneling protocols — IPsec, GRE, VPN overlays.

Responsibilities

• Cellular failover and multi-WAN state machines with sub-second transitions.
• LED indication logic for device status across WAN scenarios.
• Modem health monitoring and subsystem restart/recovery.
• Cloud-managed device configuration and telemetry reporting via MQTT.
• Secure cloud connectivity using mTLS and certificate-based authentication.
• Factory reset, firmware upgrade, and persistent storage management.
• IPv4/IPv6 dual-stack routing and WAN failover across interfaces.
• WiFi radio configuration and performance optimization across supported chips.

Skills

Embedded C

Linux

OpenWrt/OpenSync

LTE/5G cellular

Networking

GitLab

WiFi drivers

Kernel debugging

Cross-compilation

TLS security

Tools

OpenWrt build system

GDB

tcpdump

Make

Job description

The Embedded C Developer role at Themesoft Inc. focuses on building and maintaining OpenWrt-based gateways with OpenSync, enabling LTE/5G cellular backup and multi‑WAN resiliency. You will work on OpenWrt firmware, OVSDB-based cloud configuration, and secure, scalable device management.

Ideal candidates have strong C expertise on Linux, hands-on OpenWrt/OpenSync experience, and a track record with cellular modems, WiFi drivers, and kernel debugging. Onsite Englewood, CO welcomed.