Keeping Single-Use Temperature Loggers Out of Landfills — By Turning Them Into Dev Boards
Designed for single-use tracking of materials shipped in a cold-chain environment, these disposable tags hide a wealth of hardware within.
Pseudonymous maker "arduinocelentano," hereafter simply "Celentano," has written a guide to salvaging single-use supply chain temperature monitors in order to recover the surprisingly powerful microcontrollers within — turning them into reusable development boards instead of sending them off for recycling or into landfill.
"These small devices are used to track the temperature of sensitive materials (like medicine, food etc.) during [its] transportation," Celentano explains. "They are usually single-use devices and considered to be e-waste as soon as a cargo container is delivered. Yes, imagine thousands of trucks all around the world delivering thousands of boxes with implanted little pieces of hardware destined to become a heap of e-waste just after few days of operating. I disassembled several samples and found out that some of them might be reprogrammed and repurposed with a little bit of reverse engineering."
Celentano's work focuses on the Q-tag, which upon disassembly turned out to have STmicroelectronics STM32L152 microcontrollers within — boasting a flexible Arm Cortex-M3 core running at up to 32MHz and ultra-low-power operating modes along with a fast 12-bit analog-to-digital converter (ADC) offering up to one mega-samples per second (MSPS) resolution.
"To detect which [pin] is which, you’ll need a multimeter set to continuity mode and a datasheet for your MCU [Microcontroller Unit]," Celentano explains of how to find the Serial Wire Debug (SWD) required to reprogram the microcontroller and remove its stock temperature-tracking functionality. "Touch gently [the] MCU's pin and a pad on the PCB with your probes to detect whether they are connected. At least you’ll need to detect VCC3.3V, GND, SWDIO and SWDCLK pads to be able to program the microcontroller."
Once the layout is determined, pins or wires can be soldered to provide a connection to a programming tool — the STMicro ST-LINK, in the case of Celentano's Q-tag boards. "When you are sure that everything works, you may install STM32CubeIDE or configure an open-source development environment," the maker adds. "Now you have an affordable development board, and it’s up to you to decide how to use it. Maybe it might be possible to port Arduino to it and implement a USB bootloader or build some customized HID device."
The full write-up is available on Celentano's Hackaday.io page.