UFTDI(4) FreeBSD Kernel Interfaces Manual UFTDI(4)
NAME
uftdi - Future Technology Devices International USB to serial UART driver
SYNOPSIS
device usb
device ucom
device uftdi
In rc.conf(5):
kld_list="uftdi"
In sysctl.conf(5):
hw.usb.uftdi.debug=1
hw.usb.uftdi.skip_jtag_interfaces=0
DESCRIPTION
The uftdi driver supports FTDI USB to serial UART devices. If the
appropriate hardware is detected, the driver will be loaded automatically
by devmatch(8). To load the driver manually, add it to the kld_list in
rc.conf(5), or use kldload(8) at runtime. The device is accessed through
the ucom(4) driver which makes it behave like a tty(4).
Call out through this interface with applications like cu(1) or tip(1).
HARDWARE
The uftdi driver supports the following USB to serial UART controllers:
o FTDI FT4232H
o FTDI FT232R
o FTDI FT230X
o FTDI FT2232H
o FTDI FT2232D
o FTDI FT2232C
o FTDI FT8U232BM
o FTDI FT8U232AM
o FTDI FT8U100AX
SYSCTL VARIABLES
These settings can be entered in the loader(8) prompt, set in
loader.conf(5), sysctl.conf(5), or changed at runtime with sysctl(8):
hw.usb.uftdi.debug Enable debugging messages, default `0'
hw.usb.uftdi.skip_jtag_interfaces Ignore JTAG interfaces, default `1'
IOCTLS
Many of the supported chips provide additional functionality such as
bitbang mode and the MPSSE engine for serial bus emulation. The uftdi
driver provides access to that functionality with the following ioctl(2)
calls, defined in <dev/usb/uftdiio.h>:
UFTDIIOC_RESET_IO (int)
Reset the channel to its default configuration, flush RX and TX
FIFOs.
UFTDIIOC_RESET_RX (int)
Flush the RX FIFO.
UFTDIIOC_RESET_TX (int)
Flush the TX FIFO.
UFTDIIOC_SET_BITMODE (struct uftdi_bitmode)
Put the channel into the operating mode specified in mode, and
set the pins indicated by ones in iomask to output mode. The
mode must be one of the uftdi_bitmodes values. Setting mode to
UFTDI_BITMODE_NONE returns the channel to standard UART mode.
enum uftdi_bitmodes
{
UFTDI_BITMODE_ASYNC = 0,
UFTDI_BITMODE_MPSSE = 1,
UFTDI_BITMODE_SYNC = 2,
UFTDI_BITMODE_CPU_EMUL = 3,
UFTDI_BITMODE_FAST_SERIAL = 4,
UFTDI_BITMODE_CBUS = 5,
UFTDI_BITMODE_NONE = 0xff,
};
struct uftdi_bitmode
{
uint8_t mode;
uint8_t iomask;
};
Manuals and application notes published by FTDI describe these
modes in detail. To use most of these modes, you first put the
channel into the desired mode, then you read(2) and write(2) data
which either reflects pin state or is interpreted as MPSSE
commands and parameters, depending on the mode.
UFTDIIOC_GET_BITMODE (struct uftdi_bitmode)
Return the current bitbang mode in the mode member, and the state
of the DBUS0..DBUS7 pins at the time of the call in the iomask
member. The pin state can be read while the chip is in any mode,
including UFTDI_BITMODE_NONE (UART) mode.
UFTDIIOC_SET_ERROR_CHAR (int)
Set the character which is inserted into the buffer to mark the
point of an error such as FIFO overflow.
UFTDIIOC_SET_EVENT_CHAR (int)
Set the character which causes a partial FIFO full of data to be
returned immediately even if the FIFO is not full.
UFTDIIOC_SET_LATENCY (int)
Set the amount of time to wait for a full FIFO, in milliseconds.
If more than this much time elapses without receiving a new
character, any characters in the FIFO are returned.
UFTDIIOC_GET_LATENCY (int)
Get the current value of the latency timer.
UFTDIIOC_GET_HWREV (int)
Get the hardware revision number. This is the bcdDevice value
from the usb_device_descriptor.
UFTDIIOC_READ_EEPROM (struct uftdi_eeio)
Read one or more words from the configuration eeprom. The FTDI
chip performs eeprom I/O in 16-bit words. Set offset and length
to values evenly divisible by two before the call, and the data
array will contain the requested values from eeprom after the
call.
struct uftdi_eeio
{
uint16_t offset;
uint16_t length;
uint16_t data[64];
};
The FT232R chip has an internal eeprom. An external serial
eeprom is optional on other FTDI chips. The eeprom may contain
64, 128, or 256 words, depending on the part used. Multiple
calls may be needed to read or write the larger parts. When no
eeprom is present, all words in the returned data are 0xffff. An
erased eeprom also reads as all 0xffff.
UFTDIIOC_WRITE_EEPROM (struct uftdi_eeio)
Write one or more words to the configuration eeprom. The
uftdi_eeio values are as described for UFTDIIOC_READ_EEPROM.
The FTDI chip does a blind write to the eeprom, and it will
appear to succeed even when no eeprom is present. To ensure a
good write you must read back and verify the data. It is not
necessary to erase before writing. Any position within the
eeprom can be overwritten at any time.
UFTDIIOC_ERASE_EEPROM (int)
Erase the entire eeprom. This is useful primarily for test and
debugging, as there is no need to erase before writing. To help
prevent accidental erasure caused by calling the wrong ioctl, you
must pass the special value UFTDI_CONFIRM_ERASE as the argument
to this ioctl.
FILES
/dev/ttyU* for callin ports
/dev/ttyU*.init
/dev/ttyU*.lock corresponding callin initial-state and lock-state
devices
/dev/cuaU* for callout ports
/dev/cuaU*.init
/dev/cuaU*.lock corresponding callout initial-state and lock-state
devices
SEE ALSO
cu(1), tty(4), ucom(4), usb(4)
HISTORY
The uftdi driver appeared in FreeBSD 4.8 from NetBSD 1.5.
FreeBSD 15.1-STABLE-HBSD June 25, 2025 UFTDI(4)