The I2C TCTI FTDI can be used for communication with an I2C-based TPM over the FTDI MPSSE USB to I2C bridge. The FTDI module utilizes the tcti-i2c-helper library for handling the PTP I2C protocol and the libftdi-dev library for handling the USB to I2C communication.
Example of a FTDI MPSSE USB to I2C bridge is the product “USB 2.0 Hi-Speed to MPSSE Cable (SPI/I2C/JTAG master) with +3.3V digital level signals”, part no: C232HM-DDHSL-0. Connect the cable to your TPM as specified in the table below:
| C232HM-DDHSL-0 | Description |
|---|---|
| pin 1, red, VCC | VCC |
| pin 2, orange, SCL | SCL |
| pin 3, yellow, SDA | SDA |
| pin 4, green, SDA | SDA |
| pin 10, black, GND | GND |
Important: both yellow and green wires need to be shorted together to create bidirectional data.
Set udev rules for the C232HM-DDHSL-0 cable by creating a file /etc/udev/rules.d/60-c232hm.rules:
ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6014", TAG+="uaccess"
Activate the udev rules:
sudo udevadm control --reload
You should see the following after plugging in the C232HM-DDHSL-0 cable:
dmesg [74386.091721] usb 3-2: new high-speed USB device number 18 using xhci_hcd [74386.439103] usb 3-2: New USB device found, idVendor=0403, idProduct=6014, bcdDevice= 9.00 [74386.439117] usb 3-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [74386.439129] usb 3-2: Product: C232HM-DDHSL-0 [74386.439140] usb 3-2: Manufacturer: FTDI [74386.439151] usb 3-2: SerialNumber: FT1UGJKF [74386.443996] ftdi_sio 3-2:1.0: FTDI USB Serial Device converter detected [74386.444030] usb 3-2: Detected FT232H [74386.446370] usb 3-2: FTDI USB Serial Device converter now attached to ttyUSB0
Use tcti-i2c-ftdi to communicate with a I2C-based TPM:
tpm2_startup -Ti2c-ftdi -c tpm2_getrandom -Ti2c-ftdi 8 --hex
Enable abrmd:
export DBUS_SESSION_BUS_ADDRESS=`dbus-daemon --session --print-address --fork` tpm2-abrmd --allow-root --session --tcti=i2c-ftdi & export TPM2TOOLS_TCTI="tabrmd:bus_name=com.intel.tss2.Tabrmd,bus_type=session" tpm2_startup -c tpm2_getrandom 8 --hex