In Thermal Ink printers, Ink supplies include a security chip to properly identify the supplies and control
the remaining ink quantity. This security smart chip is owned by each brand and optimized to ensure the
robustness in front hacker attacks and counterfeiting.
Smart-chip communication with the host printer uses I2C serial bus protocol which is a wide spread
industry standard. HP latest device revision includes new functionality beyond the I2C protocol which
helps the printer in trying to recognize if the smart-chip is original. The printer sends a command to the
smart-chip, which in response pulls down the I2C data line during a certain time; an HP original chip is
expected to respond precisely, meeting the time interval.
Enabling the ability of doing time measurements on the I2C data line typically requires extra Hardware
resources and the redesign of the existing electronics. Such modification takes time to design and
complete the validation of the new hardware and can lead to cost increments.
The implementation presented enables the capacity to send the I2C commands, check if the smart-chip
pulls down the data line and the certain time measurement only with the I2C serial bus dedicated pins.
Not adding more resources and without changing the PCA design.
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INC, HP, "I2C BASED SECURITY INK SUPPLY SMART-CHIP RECOGNITION", Technical Disclosure Commons, (January 24, 2020)