Purging the internal transmit buffer of FT201X I2C-Slave - c++

Question

Im trying to purge the FX-Buffer of the FT201X I2C-Slave. Somehow it seems not to work, the master still reads old data sets even after the purge-function is called. Im using C++(Visual Studio 2019) with the D2XX-functions given in the D2XX-Programmers-Guide.
I did try to use the StopInTask and RestartInTask functions before and after the purge command, but it still does not clear my buffer.
status = FT_StopInTask(fthandle);
if (status != FT_OK) {
printf("status not ok %d\n", status);
}
status = FT_Purge(fthandle, FT_PURGE_TX); // Purge Tx buffer
if (status != FT_OK) {
printf("status not ok %d\n", status);
}
status = FT_RestartInTask(fthandle);
if (status != FT_OK) {
printf("status not ok %d\n", status);
}
I did even try FT_W32_PurgeComm(fthandle, PURGE_TXABORT | PURGE_TXCLEAR), the buffer still appears to not be cleared, even if the function returns true.

Answer 1

Somehow FT_Purge(fthandle, FT_PURGE_RX) clears both buffers, the buffer that stores the data coming from the host (sent via FT_Write) as well as the buffer that stores data coming from an external I2C-Master. Mapping the signal RXF (value: 10) to a CBUS-pin and reading the pins with FT_GetBitMode works to indicate if the buffer that stores data from the host is empty.