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"Internet-connected devices [are] not always necessary if you don’t need real-time updates. Whether it’s due to battery life, or location and range constraints, downloading data directly from the device whenever possible might be a viable solution"
cuplTag is a battery-powered NFC tag that logs ambient temperature and humidity. Tap it with an NFC-enabled phone and you will see timestamped readings appear in a web application. It’s a one-step operation that requires no configuration and no app installation!
Tap cuplTag with your phone to see temperature and humidity in an instant. It works like this:
¹ Sensor readings are encoded in a ~1 KB circular buffer within the URL.
² The URL is written to a dual interface EEPROM using I²C, which is readable from a phone using NFC.
³ Time interval is configurable from 3 minutes to 65535 minutes.
The cuplTag system offers unparalleled ease-of-use in a low cost package. There are many uses for this zero-install sensor. Here are just a few:
Your cuplTag will be fully operable as soon as you insert a battery. cuplTags are pre-configured to display data using an instance of cuplfrontend that is hosted by our company, Plotsensor, Ltd. You are free to re-configure your tag so it uses your own instance of the cupldeploy web application.
Newly captured data are seamlessly stitched together with data from previous tag scans. You can easily see graphs of sample data with high temporal resolution by scanning cuplTag every few days.
The cupldeploy project is the parent of cupltag and the web application, which consists of cuplbackend and cuplfrontend. A tagged commit of cupldeploy represents a system version number (e.g. D3.7). Interoperable versions of each child project will share the same version number.
Authentication is important because tag data will be written to a database. In order to deter spoofing, each cuplTag ships with a unique and random secret key, which is used to generate an HMAC that is updated whenever the contents of the circular buffer change. (You can learn more about the specifics in our documentation). The HMAC is verified by the cupl web application, which knows the secret key. This feature prevents anyone without a cuplTag from generating a URL that appears to have come from one. The HMAC also guards against replay attacks, where a valid URL is obtained by a third party and fed to the web application more than once. It is highly unlikely that a cuplTag will produce the same HMAC twice.
For more detailed technical specifications, please see the cuplTag datasheet.
cuplTag is a system comprised of hardware, firmware, frontend software, and a backend web applications, all of which are open source. That includes:
We welcome your questions through the Ask a technical question link below.
The cuplTag PCBA will be assembled by our contract electronics manufacturer (CEM) in China. We have ordered 250 units up front. To prevent the global chip shortage from slowing production, we have acquired reels of four components in advance. They will be free-issued to the CEM.
In response to a shortage of the MSP430FR2155TDBTR microcontroller, we have sourced an alternate part (MSP430FR2355TDBTR) for the first batch. This component, which is in the same family, is identical but for the addition of one peripheral (SAC) that is unused by cuplTag and disabled by default.
PCBAs will be shipped from the CEM to Plotsensor, Ltd. in Oxfordshire, UK, at which point we will:
After testing and packaging the production batch of cuplTags, we will send them on to Crowd Supply’s fulfillment partner, Mouser Electronics, who will distribute them to backers worldwide. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.
The two most significant risks we face pertain to the global chip shortage and our decision to use a new contract electronics manufacturer (CEM) for the cuplTag production run.
No problems are expected with the first 250 units that ship from Crowd Supply. We obtained components in advance, and these units are already in production. After this first batch is shipped, however, we face the possibility of delays on subsequent manufacturing runs. Fortunately, with only 16 unique components in the BOM, cuplTag does not require us to source very many parts.
To sell cuplTag at a lower price, we have switched to a larger Chinese CEM. Prototypes were made with a European PCBA manufacturer. In order to reduce the risk of delays caused by a misunderstandings or an error, the CEM will ship us 10 fully populated PCBAs for inspection before we approve the remaining 240.