Here we try to document what we know about the EEPROM Structure. Even with a 93xx66 EEPROM, at maximum 256 Bytes are used All important things happen in the first 0x14(FT232/245), 0x16(FT2232CD), 0x18(FT232/245R) or 0x1a (FT2232H/4432H) bytes Type | Use extra EEPROM space FT2XXB | No Byte.BIT| TYPE_AM TYPE_BM TYPE_2232C TYPE_R TYPE_2232H TYPE_4232H 00.0 | 0 0 channel_a_type 232R/245R channel_a_type 0 00.1 | 0 0 channel_a_type channel_a_type 0 00.2 | 0 0 channel_a_type high_current channel_a_type 0 00.3 | 0 0 channel_a_driver channel_a_driver channel_a_driver channel_a_driver 00.4 | 0 0 high_current_a 0 0 0 00.5 | 0 0 0 0 0 0 00.6 | 0 0 0 0 0 0 00.7 | 0 0 0 0 SUSPEND_DBUS7 channel_c_driver On TYPE_R 00.0 is set for the FT245R and cleared for the FT232R On TYPE_R 00.3 set means D2XX, on other devices VCP 01.0 | 0 0 channel_b_type channel_b_type 0 01.1 | 0 0 channel_b_type channel_b_type 0 01.2 | 0 0 channel_b_type 0 channel_b_type 0 01.3 | 0 0 channel_b_driver 0 channel_b_driver channel_b_driver 01.4 | 0 0 high_current_b 0 0 0 01.5 | 0 0 0 0 0 0 01.6 | 0 0 0 0 0 01.7 | 0 0 0 0 0 channel_d_driver Fixme: Missing 4232H validation 02 | Vendor ID (VID) LSB (all) 03 | Vendor ID (VID) MSB (all) 04 | Product ID (PID) LSB (all) 05 | Product ID (PID) MSB (all) 06 | Device release number LSB (not tested on TYPE_4232H) 07 | Device release number MSB (not tested on TYPE_4232H) | 08.4 | Battery powered 08.5 | Remote wakeup 08.6 | Self powered: 1, bus powered: 0 08.7 | Always 1 | 09 | Max power (mA/2) | Byte.BIT| TYPE_AM TYPE_BM TYPE_2232C TYPE_R TYPE_2232H TYPE_4232H 0a.0 | 0 IsoIn IsoIn part A 0 0 0 0a.1 | 0 IsoOut IsoOut part A 0 0 0 0a.2 | 0 suspend_pull_down suspend_pull_down suspend_pull_down suspend_pull_down 0a.3 | 0 use_serial use_serial use_serial 0a.4 | 0 change_usb_version change_usb_version 0a.5 | 0 0 IsoIn part B 0 0 0 0a.6 | 0 0 IsoOut part B 0 0 0 0a.7 | 0 - reserved 0b | TYPE_R Bitmask Invert, 0 else Byte.BIT| TYPE_4232H 0b.4 | channel_a_rs485enable 0b.5 | channel_b_rs485enable 0b.6 | channel_c_rs485enable 0b.7 | channel_d_rs485enable Byte | TYPE_AM TYPE_BM TYPE_2232C TYPE_R TYPE_2232H TYPE_4232H 0c | 0 USB-VER-LSB USB-VER-LSB 0 ? ? 0d | 0 USB-VER-MSB USB-VER-MSB 0 ? ? (On several FT2232H different values were observed -> The value is unused if change USB version is not set, so it might contain garbage) 0e | OFFSET Vendor 0f | Len VENDOR 10 | Offset Product 11 | Length Product 12 | Offset Serial 13 | Length Serial Byte.BIT| TYPE_AM TYPE_BM TYPE_2232C TYPE_R TYPE_2232H TYPE_4232H 14.3:0 | UA UA CHIP CBUS[0] AL A 14.7:0 | UA UA CHIP CBUS[1] AH B 15.3:0 | UA UA 0 CBUS[2] BL C 15.7:0 | UA UA 0 CBUS[3] BH D 16.3:0 | UA UA UA CBUS[4] 0 0 16.7:0 | UA UA UA 0 0 0 CHIP values: 0x46: EEPROM is a 93xx46 0x56: EEPROM is a 93xx56 0x66: EEPROM is a 93xx66 17 UA UA UA 0 0 0 18 UA UA UA VENDOR CHIP CHIP 19 UA UA UA VENDOR 0 0 1a UA (all) Additional fields after the serial string: 0x00, 0x00 - reserved for "legacy port name prefix" 0x00, 0x00 - reserved for plug and play options (Observed values with PnP == 0: 0x02 0x03 0x01 0x00) Note: The additional fields after the serial number string collide with the official FTDI formula from AN_121 regarding the start of the user area: "Start Address = the address following the last byte of SerialNumber string."