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+++ b/doc/DUART28-EEPROM-manual	Mon Sep 11 01:06:03 2023 +0000
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+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