The I2C TCTI helper can be used for TPM communication over I2C e.g. in embedded systems. It uses user supplied methods for I2C and timing operations in order to be platform independent. These methods are supplied to Tss2_Tcti_I2c_Helper_Init via the TSS2_TCTI_I2C_HELPER_PLATFORM struct.
Documentation detailing the implementation of platform methods can be found in tss2_tcti_i2c_helper.h. For an example implementation that uses the I2C TCTI helper to communicate with an I2C-based TPM over the FTDI MPSSE USB to I2C bridge, refer to the tcti-i2c-ftdi module.