Dániel Buga's Card/IO Is a Single-Lead ECG Business Card That Really Puts Your Finger on the Pulse

Electrical engineer Dániel Buga has built a business card that really shows his finger is on the pulse — quite literally, as the Card/IO serves as a single-lead electrocardiogram (ECG) monitor, plotting the holder's heart rate on-screen.

"Card/IO is an open source single-lead ECG implemented as a business card-like device, and its surrounding software systems," Buga explains. "[The design] is a four layer PCB containing the MCU [Microcontroller Unit], display, battery, and related circuitry. The ECG frontend, ADC [Analog to Digital Converter], and touch detection/wakeup generator [are] implemented as a solder-on daughter board."

Designed to mimic the rough footprint of a business card, the Card/IO is built around an ESP32-WROOM-32 module, giving it two Tensilica Xtensa LX6 CPU cores running at up to 240MHz and integrated Bluetooth 4.2 and Wi-Fi connectivity. This module is mounted on a PCB the front of which is surprisingly spartan: two exposed copper contacts and a compact display.

Push your thumbs against those two contacts, though, and the Card/IO springs into life — using the ECG front-end daughterboard to amplify the signal from the blood pulsing through your thumbs and display it on-screen as a classic electrocardiogram (ECG).

Buga has also hinted at the possibility of using the Wi-Fi radio to connect to a cloud platform for more detailed logging and analysis — though, at the time of writing, the code for this had not been publicly released.

Those interested in building their own Card/IO can find design files and source code in the project's GitHub repositories, under the permissive MIT license. "There are some significant issues (like the device freezing)," Buga warns those looking to follow in his footsteps, "but hey, that's me!"