[SOLVED] Waxwing Spartan 6 for serial communication over FT2232H

I wanted to use the Channel B from the FT2232H for serial communication with my Waxwing Spartan 6 FPGA Board. But I can only found the following definitions in the ucf file:

Code:

NET "RXF"  LOC = "V13"  | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8 ;

NET "TXE"  LOC = "U13"  | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8 ;

NET "RD"  LOC = "V15"  | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8 ;

NET "WR"  LOC = "U15"  | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8 ;

NET "SIWUA"  LOC = "T17"  | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8 ;

But these definitions seem to be for parallel communication. Could somebody tell me the definitions for serial communication? I only found them for the Saturn board and the Saturn uses the same FT2232H chip, so I guess it would be possible for the Waxwing Board too

Thanks
Markus

 

Thanks for the fast reply But I still have trouble implementing the serial communication. I haven't tried RX yet, but when I try to transmit a byte from the FPGA to my PC I do not get the right result. Here's the code I'm using:

Code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity uart is
    port(
        I_Clk   : in std_logic;
        TX      : out std_logic;
        RX      : in std_logic
    );
end uart;

architecture uart_behav of uart is
    type tx_state_t is (idle, active);

    signal test_count : integer range 0 to 9 := 0;
    signal index : integer range 0 to 7 := 0;
    signal tx_clk   : std_logic := '0';
    signal tx_count : integer := 0;
    signal tx_state : tx_state_t := idle;
    signal baudrate : std_logic_vector(15 downto 0) := X"28B0"; -- 9600bps @ 100Mhz
begin
    tx_clk_gen : process(I_Clk)
    begin
        if rising_edge(I_Clk) then
            if tx_count = 0 then
                -- Chop off LSB to get a clock
                tx_count <= to_integer(unsigned(baudrate(15 downto 1)));
                tx_clk <= not tx_clk;
            else
                tx_count <= tx_count - 1;
            end if;
        end if;
    end process;

    tx_proc : process(tx_clk)
    begin
        if rising_edge(tx_clk) then
            case tx_state is
                when idle =>
                    TX <= '1';
                    tx_state <= active;
                when active =>
                    if test_count = 0 then
                        -- Start Bit
                        TX <= '0';
                        test_count <= test_count + 1;
                    elsif test_count = 9 then
                        -- Stop Bit
                        TX <= '1';
                    else
                        -- Data Bit (send all 0's)
                        TX <= '0';
                        test_count <= test_count + 1;
                    end if;
            end case;
        end if;
    end process;
end uart_behav;

This should result in 0x00 to be sent to the receiver. But this is the result I get:

Code:

000022.394 RX   0000  F9

I get 0xF9 back...I don't know what I'm doing wrong, but here's the python script I use to receive over the serial port(btw im running Linux):

Code:

#!/usr/bin/env python3
""" Serial communication """

import time
import serial

# baudrate = 1500000  # 1.5Mbit/s
# baudrate = 12000000 # 12Mbit/s

# One byte takes 10 bits so 10Mbit/s may almost equal 1.0MByte/s.

ser = serial.serial_for_url("spy:///dev/ttyUSB1?file=test.txt", timeout=1, baudrate=9600)

time.sleep(1)

msg = ""
value = None
error = 0
while True:
    value = ser.read()
    try:
        msg += value.decode("ascii")
        print(msg[-1], end="", flush=True)
    except:
        pass
print("\n")

EDIT: Is there anything else I need to configure for the chip to work with my linux box?

EDIT2: My ucf file:

Code:

CONFIG VCCAUX = "3.3" ;

    NET "I_Clk"                     LOC = V10 | IOSTANDARD = LVCMOS33 | PERIOD = 100MHz;
    NET "RX"                      LOC = N11   | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8;
    NET "TX"                      LOC = M11   | IOSTANDARD = LVCMOS33 | SLEW = FAST | DRIVE = 8;

EDIT3: Update: So whatever value I choose to send over the UART looks fine in the simulation but even when I continously sent bytes to my PC (in a loop) only one byte is received and that is 0xF9. So I do think that the configuration of either my driver (using libftdi) or the chip is wrong. I did saw an article on how to change the configuration of the FTDI chip for the Saturn device on Windows(which seems to be what I need for my Waxwing board aswell), but have not found an equalivent for linux and I also do not have any windows box available right now to change the config.

 

I finally got access to a windows box to check the config of the FTDI chip. I changed the config for channel B to RS232 UART and switched back to my linux box and it worked perfectly!

Thanks for the great help!