The new user-friendly (or fool-proof) way to examine and change DUART28 adapter
configuration is fc-duart28-conf utility described in the DUART28-EEPROM-config
article.  The present article describes the older method that existed before
fc-duart28-conf, and which is used for initial factory programming.

Determining your current DUART28 config
=======================================

Connect the USB cable between your DUART28 board and your Linux host, and
observe dmesg output.  If your DUART28 board is in the C configuration, it will
present as USB ID 0403:7152, and if it is in the S config, it will present as
USB ID 0403:6010.  You can also see these USB IDs with lsusb.  The product ID
string is also programmed as "DUART28C" or "DUART28S".

Converting from DUART28S to DUART28C
====================================

If your DUART28 board is currently in the S config (or if you messed it up and
have a blank or corrupt EEPROM), its USB ID will be 0403:6010, which is the
default ID for FTDI's two-channel FT2232x family.  Because it is the standard
default, there are plenty of other gadgets using the same ID - thus you need to
ensure that you have no other USB devices with the same ID connected to your
system during the reprogramming operation.  Run lsusb and ensure that you see
only one USB device with ID 0403:6010.  Ensure that this one device really is
your DUART28 board: unplug that USB cable and make sure that the device
disappears, plug it back in and make sure that it reappears.

One you have confirmed that you won't inadvertently hit some other FT2232x
device, execute the actual programming command, which is a shell pipeline:

ftee-gen2232c duart28c $Serial | fteeprom-prog i:0x0403:0x6010

(See FTDI-EEPROM-tools article for other ways to specify the target device to
 fteeprom-prog.)

Replace the $Serial metavariable with the 3-digit serial number of your DUART28
adapter board as it appears on the factory serial number sticker.

After this operation completes successfully, unplug and replug the USB cable
between the DUART28 board and your host - the adapter should now show up with
USB ID 0403:7152.

Converting from DUART28C to DUART28S
====================================

If your DUART28 board is currently in the C config, its USB ID will be
0403:7152, which is a private ID that belongs to us and should not be used by
other parties.  The reverse conversion command is as follows:

ftee-gen2232c duart28s $Serial | fteeprom-prog i:0x0403:0x7152