Writing to the chip with FT245 synchronous mode

I am using the FT232H device connected to the FPGA, and I am trying to write some bytes to it. Reading (transfer FPGA->PC) works perfectly, but writing (transfer PC->FPGA) do not work at all. I am using following code:

libusb_open(board, &board_handle);
if (libusb_kernel_driver_active(board_handle, 0) == 1) {
    if(libusb_detach_kernel_driver(board_handle, 0) == 0);
}
libusb_set_configuration(board_handle, 1);
libusb_claim_interface(board_handle, 0);
libusb_control_transfer(board_handle, 0x40, 0x0B, 0x00FF, 0x01, NULL, 0, 5000);
libusb_control_transfer(board_handle, 0x40, 0x0B, 0x40FF, 0x01, NULL, 0, 5000);
libusb_bulk_transfer(board, 0x02, bufout, 3, &transfered, 5000);
bufin = calloc(512, 1);
libusb_bulk_transfer(board, 0x81, bufin, 512, &transfered, 5000);

Bufout is filled with data. When I am trying to send some data generated on the FPGA to the PC there is no problem; bufin is filled with correct data.

But when I am trying to send some data to the FPGA, and display it on leds or send it back, the problem starts.

Every byte I receive at the FPGA site is 0xFF regardless of bufout content. Bufout and bufin are both declarated as unsigned char *.

unsigned char *bufin, *bufout;

Surprisingly (or not) the number of bytes received FPGA match the number of bytes sended by the PC, but all bytes have value 0xFF.

Am I doing something wrong?

I tried using libftdi, but the effect is the same (not surprising libftdi is using libusb as an engine I think).

Maybe I forgot to call some important function on the host side?

Code on the FPGA side is also very simple:

process(ftdi_clk, sys_rst)
begin
    if sys_rst = '0'then
        ftdi_wr <= '1';
        ftdi_data <= "ZZZZZZZZ";
        ftdi_rd <= '1';
        ftdi_oe <= '1';
        read <= '1';
    elsif rising_edge(ftdi_clk) then
        if ftdi_txe = '0' then
            ftdi_wr <= '0';
            ftdi_data <= buf;
        else
            ftdi_wr <= '1';
            ftdi_data <= "ZZZZZZZZ";
        end if;
        if (read = '0') and (ftdi_rxf = '0') then
            ftdi_rd <= '0';
            buf <= ftdi_data;
        else
            ftdi_rd <= '1';
        end if;
        if ftdi_rxf = '0' then
            ftdi_oe <= '0';
            read <= '0';
        else
            ftdi_oe <= '1';
            read <= '1';
        end if;
    end if;
end process;

EDIT: I have checked all possible electrical configuration, pullups, i/o voltage and everything seems fine. Still all data transferred from the FTDI to the FPGA are ones, checked on 2 separate chips, so most probably it is a software problem. I have checked simulation, even post-fit simulation, communication should work according to the documentation.

EDIT2: I have tried with original vendor libraries.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ftd2xx.h>

int main(){
    FT_STATUS ftStatus;
    FT_HANDLE ftHandle;
    DWORD BytesWritten;
    unsigned char data[512];
    int i;
    FT_PROGRAM_DATA ftData = {
    0x00000000, 0xFFFFFFFF, // Headers
    0x00000005,  // Version (5 = 232H)
    0x0403, 0x6014, // VID:PID
    "StackOverflow", "Stack", "StackBoard", NULL,
    500, 0, 1, 1, // MaxPower, PnP, SelfPowered, Remote WakeUp
    // FT232B
    0, 0, 0, 0, 0, 0, 0,
    // FT2232
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    // FT232R
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    // FT2232H
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0,
    // FT4232H
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0,
    // FT232H
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0,
    0, 0, 0, 0, 0, 0, 0,
    };
    ftStatus = FT_Open(0, &ftHandle);
    ftStatus = FT_SetTimeouts(ftHandle, 5000, 5000);
    ftStatus = FT_EE_Program(ftHandle, &ftData);
    ftStatus = FT_EE_Program(ftHandle, &ftData);
    ftStatus = FT_SetBitMode(ftHandle, 0xFF, FT_BITMODE_SYNC_FIFO); 
    for(i = 0; i<512; i++) data[i] = 0x02;
    ftStatus = FT_Write(ftHandle, data, 512, &BytesWritten);
    printf("%d bytes written\n", BytesWritten);
    ftStatus = FT_Read(ftHandle, &data, 512, &BytesWritten);
    printf("%d bytes read\n", BytesWritten);
    for(i = 0; i<BytesWritten; i++) printf("%#2x ", data[i]);
    FT_Close(ftHandle);
}

Still exactly the same behavior. I have updated linux kernel to the most recent one (4.2.3) but results are the same. Sadly I checked on few different machines and 3 different chips.

Not sure if it is your only problem, but I think you have some short-circuits going on on ftdi_data. It can be driven by the FPGA at the same time as ftdi_oe is active.