Ultra-Wideband (UWB) has moved far beyond early experiments. According to ABI Research, the number of UWB-enabled devices is projected to exceed 1 billion units by 2025. While much of this growth is driven by consumer smartphones and automotive digital keys, the most challenging and profitable use cases sit in logistics, industry, healthcare, and access control. These environments demand tags that are small, secure, and capable of operating for years without battery replacement.

The Qorvo QM35 family, particularly the QM35825, has quickly become a standard platform for UWB tags. Its feature set is impressive: dual-channel operation (5 and 9), ±5 cm ranging accuracy, ±2° AoA, 104 dB link budget, and high data rates up to 62.4 Mbps. It also supports 802.15.4z secure ranging, SESIP3-level security certification, and a full Cortex-M33 MCU for application logic. Yet, as many engineering teams discover, simply having capable silicon is not enough. The firmware is where performance, efficiency, and business value are determined.

This article explores how to develop firmware for QM35-based UWB tags that balances advanced ranging performance with power efficiency, robust security, and custom application layers. Each section ties technical design decisions back to their business consequences, offering practical insights for scaling deployments from pilots to thousands of devices.

Firmware Architecture on QM35

Building UWB tag firmware for QM35 is best approached as a layered architecture:

  1. Hardware Abstraction Layer (HAL): Manages RF blocks, cryptographic accelerators, power domains, and MCU peripherals. A clean HAL ensures that hardware specifics are decoupled from upper layers, making it easier to migrate across future silicon revisions.
  2. Protocol Layer: Implements 802.15.4z ranging profiles (HRP, BPRF, HPRF), secure time-of-flight (STS), and optional AoA. This layer is also responsible for synchronization, packet framing, and retry handling.
  3. Application Layer: Encapsulates the business logic: when to wake up, what payload to send, how to process IMU triggers, or how to react when entering a geofence.

The key business value of this separation is flexibility. For example, a logistics provider may initially deploy a tag for simple location tracking (TDoA blinks). Later, the same hardware might need to send vibration or temperature data for cargo monitoring. If the firmware is layered properly, only the application layer changes—avoiding the need for expensive re-certification of the RF stack. This modularity also supports faster iteration: firmware teams can release application updates without destabilizing the core ranging engine.

Power Management Strategies for UWB Tags

For any UWB deployment, battery lifetime directly defines total cost of ownership (TCO). A tag that lasts 18 months instead of 6 months can save millions in large-scale deployments by reducing the frequency of battery replacements. With thousands of tags in circulation, every additional milliamp-hour saved per day matters.

QM35 provides extensive power management hooks, but firmware engineers must orchestrate them carefully. The main strategies include:

  • Tickless scheduling: Rather than waking the MCU on fixed intervals, the firmware should use motion detection or anchor proximity as triggers. This avoids unnecessary wake-ups in idle periods.
  • Adaptive duty cycling: Tags should dynamically adapt their ranging cadence. A tag attached to a stationary pallet does not need updates every second, while a tag on a forklift approaching a checkpoint should increase frequency.
  • Peripheral gating: The AoA subsystem, IMU sensors, and SPI buses can be powered down between operations. QM35 supports fine-grained control of these peripherals, and shutting them off often makes a bigger difference than optimizing the radio alone.
  • Short bursts at high data rates: Using the proprietary 62.4 Mbps mode reduces airtime per packet. The less time the radio spends transmitting, the lower the total energy drain, even at slightly higher instantaneous current.

Business consequence: The firmware determines how often service teams need to replace or recharge batteries. In a deployment of 10,000 tags across a logistics network, reducing replacements from every 6 months to every 18 months can save hundreds of thousands of dollars annually in labor and downtime.

Ranging Protocols and Mode Selection

QM35 tags support both Two-Way Ranging (TWR) and Time Difference of Arrival (TDoA). These are not competing protocols but tools that should be deployed selectively based on environment and business case.

Adaptive firmware strategies:

  • In sparse networks, firmware can default to TWR for robust fixes, even though the tag uses more airtime.
  • In dense RTLS deployments, firmware should use TDoA, where the tag simply sends a blink and anchors compute location, keeping tag energy low.
  • Firmware should allow dynamic mode switching—for example, tags use TDoA most of the time, but fall back to TWR if anchors fail or if entering a high-security zone.

The business relevance is twofold: minimizing anchor infrastructure costs in some cases, and minimizing tag maintenance costs in others. A single firmware build that supports both modes allows companies to cover multiple use cases with a single SKU, simplifying global logistics and certifications.

Custom Data Payloads Beyond Positioning

Modern deployments increasingly demand that UWB tags carry contextual data, not just location. A worker’s tag may need to transmit fall detection events; an equipment tag may need to send vibration data for predictive maintenance.

However, every additional byte increases airtime and energy cost. To mitigate this:

  • Firmware should use TLV encoding so that unused fields are omitted.
  • Low-priority data should be batched and sent once per minute rather than once per second.
  • Only event-driven telemetry (e.g., button press, alarm trigger) should be sent immediately.

Example payload design on QM35:

By optimizing payload design, a single UWB tag can serve multiple roles simultaneously (location + telemetry + safety) without requiring separate devices. This saves hardware costs, reduces system complexity, and strengthens business cases for UWB adoption.

Security and Integrity Considerations

As UWB becomes critical in access control, automotive digital keys, and industrial monitoring, security is non-negotiable. QM35 provides hardware-based cryptographic primitives and support for Secure Ranging (STS) under 802.15.4z.

Firmware must enforce:

  • Secure boot and secure debug: Prevents attackers from extracting firmware images or injecting malicious code.
  • Session-based authentication: Rather than appending MACs to every packet, tie payload validity to the secure ranging session, saving airtime.
  • Key rotation: Lightweight key updates ensure long-term sessions cannot be compromised.

Business importance: In automotive, regulators are moving toward requiring relay attack resistance in digital keys. In finance and healthcare, compliance regimes demand tamper-proof credentialing. Poorly implemented firmware could expose a company to not only technical failure but also regulatory fines and liability. By leveraging QM35’s SESIP3 security features correctly, firms can reduce audit costs and future-proof their deployments against tightening standards such as FiRa 3.0 and CSA Aliro.

Application Layer Customization on-Tag

A common mistake in early UWB deployments is to offload all logic to the backend. This leads to network congestion, high cloud costs, and slow response times. Instead, QM35 tags can handle local decision-making in firmware.

Practical examples:

  • Motion-qualified ranging: The tag only participates in ranging sessions when it detects movement, saving energy when stationary.
  • Context-aware updates: Tags near restricted areas increase update frequency automatically, while tags in open spaces transmit less often.
  • On-tag event detection: A fall detected via IMU can trigger an immediate emergency alert without waiting for cloud-side analysis.

These strategies directly improve user experience. Doors open faster because tags range more frequently when nearby. Worker safety alerts are delivered instantly. And cloud bandwidth costs remain manageable because irrelevant raw data never leaves the device.

Development and Testing Workflow

Developing firmware for QM35 requires more than coding—it requires a rigorous workflow.

  1. Prototype in simulation: Qorvo’s SDK provides emulation tools that help design ranging logic before deploying hardware.
  2. On-device power profiling: Measure consumption across idle, blink, TWR, and AoA scenarios.
  3. Interoperability testing: Ensure tags work seamlessly with FiRa-certified readers and anchors.
  4. Production test automation: Use Qorvo’s APS512 guidelines to validate radio performance, antenna calibration, and secure boot integrity at scale.

This structured approach minimizes surprises during scale-up. Every firmware release should be validated against automated benchmarks, ensuring that new features do not regress energy efficiency or accuracy.

Deployment Lessons from Scaling Pilots

Scaling from a 50-tag pilot to a 5,000-tag fleet typically reveals three pain points:

  1. Cadence inflation: Users demand faster updates once they see the system working. Firmware must allow OTA policies to raise update rates per zone or application without global changes.
  2. Interoperability gaps: Anchors and readers from different vendors may behave differently. Aligning with FiRa 3.0 and preparing for CSA Aliro is essential to avoid costly retrofits.
  3. Battery cost spiral: Without firmware controls (adaptive cadence, channel selection, efficient payload design), operational costs of battery replacement can exceed hardware costs within 18–24 months.

The business lesson is clear: firmware is the cost-control mechanism. Well-architected firmware reduces hidden operational expenses and ensures pilots evolve into sustainable, profitable deployments.

Conclusion

The Qorvo QM35 platform provides the raw capabilities needed for high-performance UWB tags. But those capabilities mean little without carefully engineered firmware. Decisions around power management, ranging protocol selection, payload design, security enforcement, and on-tag application logic determine whether a deployment delivers ROI or stalls in endless pilot programs.

Firmware is not a secondary technical detail – it is the strategic business lever for UWB. Organizations that treat firmware development as central will enjoy longer device lifetimes, smoother certifications, lower operating costs, and scalable deployments. Those that neglect it risk ballooning maintenance costs and security liabilities.