Environmental Sensing


A tap-to-read NFC tag that logs temperature and humidity

$2,465 raised

of $1 goal

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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 to View

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.

Use cuplTag Anywhere, Anytime

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:

At Home

In Professional Environments

cuplTag Demo

cupl Web Application

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.

cuplTag Authentication

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.

Features & Limitations

For more detailed technical specifications, please see the cuplTag datasheet.



Support & Documentation

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.

Manufacturing Plan

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:

  1. Quality Check the HT07R3 PCBAs
  2. Program the MSP430 with cuplTag firmware
  3. Write configuration strings to the MSP430 over the serial port (these specify the cuplTag serial, web application URL, etc.)
  4. Scan the cuplTag using NFC to verify that the cupl web application opens
  5. Verify that temperature and humidity readings are in line with a calibrated hygrometer manufactured by a third party
  6. Assemble the PCBA into its white plastic enclosure
  7. Stick the cupl logo on top and a CE mark on the bottom of that enclosure
  8. Ship the cuplTags in anti-static bags, together with jumpers and through-hole headers

Fulfillment & Logistics

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.

Risks & Challenges

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.

Global Chip Shortage

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.

In the Press



"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"

Ask a Question

Produced by cupl in Oxfordshire, UK.

Sold and shipped by Crowd Supply.


One cuplTag, factory configured to sample temperature and humidity at 10 minute intervals. Works with the cupldeploy platform. Requires a CR1220 battery (not included). Includes one 2x4-way 2.54 mm male header, one 1x2-way 2.54 mm male header, one 2-way 2.54 mm jumper, and printed instructions.

$29 $8 US Shipping / $18 Worldwide

40 Jumper Wires - Female/Female

From the Crowd Supply Basics project.

A bundle of 40 multicolored, 7.8" (200 mm) long silicone-coated 24 AWG jumper wires with female terminations on each end. They are designed for use with standard pitch (.1", 2.54 mm) male headers.

$10 $8 US Shipping / $18 Worldwide

TI MSP-EXP430FR2355 Dev Kit

From the Crowd Supply Basics project.

Includes the EZ-FET, a basic, low-cost MSP430 programming and debugging solution

An EVM for MSP430FRx FRAM development with onboard debug probe, Grove connector, and ambient light sensor.

$18 $8 US Shipping / $18 Worldwide

MSP-FET Flash Emulation Tool

From the Crowd Supply Basics project.

A full-featured programmer, spy-bi-wire debugger, and usb-to-serial converter for the MSP430

Connects any MSP430 MCU to a computer via USB for real-time, in-system programming and debugging. Includes a 14-conductor cable for board communication and a USB cable. Manufactured by Texas Instruments.

$153 $8 US Shipping / $18 Worldwide

About the Team


Oxfordshire, UK  ·

cupl develops NFC environmental sensors.

Malcolm Mackay

See Also

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