Obsolete RFID reader replacement
As part of a wider product development, our client came to Bluefruit Software looking for a replacement for an obsolete Radio-Frequency Identification (RFID) reader with very specific performance. Their initial investigation had shown that there were no off-the-shelf solutions meeting their requirements, as they all exhibited a shorter range or poorer anti-collision performance, even with a radio frequency (RF) power equivalent to the existing device.
Initially, we offered to start with a consultancy phase to help all stakeholders decide what would be the best way forward. A comparison highlighting the benefits and risks of three approaches for the reader was carried out:
- Reverse-engineer the obsolete design
- Develop a new digital control circuit, whilst keeping as much of the existing Analogue Front End (“hybrid” design)
- Start fresh with a completely new design (“blank slate” approach)
Performance criteria and functional requirements were also refined. We produced a report summarising our findings and recommendations, which we discussed with our client. They chose to go ahead with the hybrid approach, as it seemed to be the best trade-off between performance, risks and schedule constraints.
Refining the approach
Our client was keen to select a turnkey solution encompassing hardware and software design, which we could provide. The team coordinated development on both fronts, with regular demos to allow for short feedback loops. As we made progress, requirements were further refined, and implementation tested against concrete use cases for the reader.
Starting from scratch
A big challenge was working out the exact requirements for driving the replicated Analogue Front End of the RFID reader, with no correct schematic or detailed documentation available. Unlike most modern designs, the hybrid approach required implementing the ISO15693 RFID protocol from scratch, based on the ISO standard documents.
The obsolete design came with little supporting technical documentation, so our team took great care in investigating what made it achieve such high performance, which required several iterations.
A close collaboration
Throughout the whole process, we worked together with our client and updated them on any problem we came across that could impact their budget and schedule. We also thoroughly tested performance in accordance with jointly agreed acceptance criteria. We even designed our own 3D printed test rig accessory, to guarantee reproducibility, as well as a software tool for stress testing. All along, the hardware and software teams worked closely together to maximise velocity and value for our client.
As part of our development process, we also provided an audit trail of any changes made to the code, with systematic code reviews, as well as a record of any major design decision.
Our team has now completed the design for the replacement RFID reader and is providing support for the initial production phase.
- Poor technical supporting documentation for the existing RFID reader design
- High RF performance (range and number of simultaneous tags), not matched by any off-the-shelf solution
- ISO15693 RFID protocol implementation from standard, with tight timing requirements
- Noise immunity v sensitivity trade-off
What our client gained:
- A working design replacement for their obsolete RFID reader
- Unit tested and habitable code, to build upon should further development be needed
- Short feedback loop, with changes made following client feedback
- All-in-one software and hardware offering, with teams working closely together, and a clear communication interface
- Regular demos and release candidate binaries for early feedback
- De-risked critical aspects of the project for maximum confidence going forward, with an iterative approach for both hardware and software (for example, explored two possible hardware designs in parallel to prioritise schedule)
- A responsive development team that enabled the project to adapt to new requirements as progress was made and problems were hit
- Associated testing tools (3D-printed test rig, stress-test script)
- Architecture decision records to keep track of why design decisions were made
A team for any stage of the product development journey
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