Background – Purpose of the Project
Induction system for demanding foodservice traylines and room service operations
RFID retrofit for foodservice operations requires reliable, compatible, and robust technology — especially in environments where metal, high temperatures, and powerful induction heating elements are involved. Our client manufactures specialist food heating devices for professional applications such as hospital or hotel services. Their devices stand out from the competition because they are made using the highest quality materials, which makes them a top quality product.
The induction charger uses a number of unique solutions, some of which have been patented. One of them is a special plastic 1-piece, molded plate on which the food is heated. The plate/base is equipped with a small RFID tag on the bottom side. This tag stores information about the heating time and the time that has passed since the last heating of the food. The base contains an internal phase charging material to retain temperatures longer and reduce energy input.
Inside the cooker (charger) there is an RFID reader with an external RFID antenna. The environment is high temperature, high metalwork, and high electrical power used to supply a very close proximity several kilowatt heating element.
When their previous RFID reader supplier discontinued production, the client needed a reliable RFID retrofit for foodservice equipment — and turned to us for a solution.
Challenges to Address
- The primary challenge was to reverse engineer the API (interface specification) between the existing host electronics and the now obsolete RFID reader and replicate this with a reader we could supply based on our Pepper C1 product range.
- Secondly, obtaining sufficient and robust RFID performance in such a noisy and high metalwork environment was a major task.
- Thirdly, achieving cost efficiency of the new solution was a challenge Eccel successfully overcame.
Technology Developed
The first task was to verify whether the tags used in the plates could be recognized by our readers. It turned out that two types of tags were installed in the plates – one custom, designed before any of the standards such as ISO 15693 or ISO 14443A were established, and the other based on the well-known and open standard ISO 15693 (popular NXP ICODE SLI S). The first type of tag was „invisible” to all currently produced RFID readers or sniffers like the Proxmark device and the customer agreed to get them of. The second tag was easily recognized by our Pepper C1 reader. So we could proceed to the next steps.
The second challenge was to match the shape and size of the antenna and reader so that they were similar to the size and shape of the existing reader and antenna.
Thanks to the universal size of the Pepper C1 EA and convenient mounting holes as well as our standard 25×25 antennas, this task was not difficult. Both elements fit out-of-the-box and could be installed inside the charger housing without any major modifications. In order to maintain full compatibility, instead of our standard goldpin connectors, we used the original MOLEX connector – the same as used in the existing readers, and a step down converter that lowers the supply voltage from 12V to 5V, which is required by the Pepper C1. A new, custom reader was designed based on our Pepper C1 EA reader with the above-mentioned changes.
After installing the antenna in its place – around many metal elements, it had to be tuned. Our standard antennas are tuned for use in open air. When you insert such an antenna into a metal housing, the presence of metal causes the entire system to detune (you can read more about this here). For this purpose, we performed in situ tuning and managed to obtain a satisfactory reading range.
The next task was to get known the communication protocol between the old reader and the host device. Fortunately, the customer provided us some user manuals (15 years old) where all commands were described. The communication between these devices was based on a 5V UART TTL serial interface, so it was relatively easy to connect a logic analyser to the TX and RX lines of the UART interface and sniff all data frames sent back and forth between devices.
We implemented an additional communication protocol in the C1 firmware (in addition to our binary protocol) that supported the same commands as the old reader. Thanks to this, the Pepper C1 behaved exactly like the old reader – it simulated the old reader interface protocol.
However, after putting everything together and starting it up, the device did not work properly. After some debugging, we discovered that the timings in communication with the host were very important. Our reader sometimes responded too quickly to commands coming from the host. After implementing several optimizations features in the code, the device started working properly.
In order to reduce production costs, we also proposed that the external antennas be made using a coaxial cable instead of a thick two-wire cable. This allowed us to reduce costs and significantly reduce the time needed to assembly these antennas.
The Final Product – RFID Reader with an external antenna
The customer initially ordered 50 sets of new readers and antennas. They installed them in their devices and sent them to their regular customers so that they could become beta testers of the new solution. Several of them reported some feedback regarding the specific functions of the reader.
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The comments received from real-world users turned out to be invaluable to achieve exact performance replication, and we implemented fixes to the code. Thanks to the fact that these readers can also operate in “C1 mode”, i.e. behave like a standard Pepper C1 reader, our customer could easily upload the new firmware binary files using the built-in “over the air” (OTA) update option.
The firmware is encrypted with AES256 encryption, and the readers have encryption keys stored in a non-volatile, secured memory area, so even if the firmware files fell into the wrong hands, it would not be possible to decrypt or install it on another device.
The new readers were accepted and put into production, and this satisfied customer approached us with another project.
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