man/man4/uftdi.4

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.Dd June 25, 2025
.Dt UFTDI 4
.Os
.Sh NAME
.Nm uftdi
.Nd Future Technology Devices International USB to serial UART driver
.Sh SYNOPSIS
.Cd "device usb"
.Cd "device ucom"
.Cd "device uftdi"
.Pp
In
.Xr rc.conf 5 :
.Cd kld_list="uftdi"
.Pp
In
.Xr sysctl.conf 5 :
.Cd hw.usb.uftdi.debug=1
.Cd hw.usb.uftdi.skip_jtag_interfaces=0
.Sh DESCRIPTION
The
.Nm
driver supports FTDI USB to serial UART devices.
If the appropriate hardware is detected,
the driver will be loaded automatically by
.Xr devmatch 8 .
To load the driver manually, add it to the
.Ic kld_list
in
.Xr rc.conf 5 ,
or use
.Xr kldload 8
at runtime.
The device is accessed through the
.Xr ucom 4
driver which makes it behave like a
.Xr tty 4 .
.Pp
Call out through this interface with applications like
.Xr cu 1
or
.Xr tip 1 .
.Sh HARDWARE
The
.Nm
driver supports the following USB to serial UART controllers:
.Pp
.Bl -bullet -compact
.It
FTDI FT4232H
.It
FTDI FT232R
.It
FTDI FT230X
.It
FTDI FT2232H
.It
FTDI FT2232D
.It
FTDI FT2232C
.It
FTDI FT8U232BM
.It
FTDI FT8U232AM
.It
FTDI FT8U100AX
.El
.Sh SYSCTL VARIABLES
These settings can be entered in the
.Xr loader 8
prompt, set in
.Xr loader.conf 5 ,
.Xr sysctl.conf 5 ,
or changed at runtime with
.Xr sysctl 8 :
.Bl -tag -width "hw.usb.uftdi.skip_jtag_interfaces"
.It Va hw.usb.uftdi.debug
Enable debugging messages, default
.Ql 0
.It Va hw.usb.uftdi.skip_jtag_interfaces
Ignore JTAG interfaces, default
.Ql 1
.El
.Sh IOCTLS
Many of the supported chips provide additional functionality
such as bitbang mode and the MPSSE engine for serial bus emulation.
The
.Nm
driver provides access to that functionality with the following
.Xr ioctl 2
calls, defined in
.In dev/usb/uftdiio.h :
.Bl -tag -width indent
.It Dv UFTDIIOC_RESET_IO Pq Vt int
Reset the channel to its default configuration, flush RX and TX FIFOs.
.It Dv UFTDIIOC_RESET_RX Pq Vt int
Flush the RX FIFO.
.It Dv UFTDIIOC_RESET_TX Pq Vt int
Flush the TX FIFO.
.It Dv UFTDIIOC_SET_BITMODE Pq Vt "struct uftdi_bitmode"
Put the channel into the operating mode specified in
.Va mode ,
and set the pins indicated by ones in
.Va iomask
to output mode.
The
.Va mode
must be one of the
.Va uftdi_bitmodes
values.
Setting
.Va mode
to
.Dv UFTDI_BITMODE_NONE
returns the channel to standard UART mode.
.Bd -literal
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;
};
.Ed
.Pp
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
.Xr read 2
and
.Xr write 2
data which either reflects pin state or is interpreted
as MPSSE commands and parameters, depending on the mode.
.It Dv UFTDIIOC_GET_BITMODE Pq Vt "struct uftdi_bitmode"
Return the current bitbang mode in the
.Va mode
member, and the state of the DBUS0..DBUS7 pins at the time
of the call in the
.Va iomask
member.
The pin state can be read while the chip is in any mode, including
.Dv UFTDI_BITMODE_NONE
(UART) mode.
.It Dv UFTDIIOC_SET_ERROR_CHAR Pq Vt int
Set the character which is inserted into the buffer to mark
the point of an error such as FIFO overflow.
.It Dv UFTDIIOC_SET_EVENT_CHAR Pq Vt int
Set the character which causes a partial FIFO full of data
to be returned immediately even if the FIFO is not full.
.It Dv UFTDIIOC_SET_LATENCY Pq Vt 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.
.It Dv UFTDIIOC_GET_LATENCY Pq Vt int
Get the current value of the latency timer.
.It Dv UFTDIIOC_GET_HWREV Pq Vt int
Get the hardware revision number.
This is the
.Va bcdDevice
value from the
.Va usb_device_descriptor .
.It Dv UFTDIIOC_READ_EEPROM Pq Vt "struct uftdi_eeio"
Read one or more words from the configuration eeprom.
The FTDI chip performs eeprom I/O in 16-bit words.
Set
.Va offset
and
.Va length
to values evenly divisible by two before the call, and the
.Va data
array will contain the requested values from eeprom after the call.
.Bd -literal
struct uftdi_eeio
{
	uint16_t offset;
	uint16_t length;
	uint16_t data[64];
};
.Ed
.Pp
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.
.It Dv UFTDIIOC_WRITE_EEPROM Pq Vt "struct uftdi_eeio"
Write one or more words to the configuration eeprom.
The
.Va uftdi_eeio
values are as described for
.Dv UFTDIIOC_READ_EEPROM .
.Pp
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
.Em not
necessary to erase before writing.
Any position within the eeprom can be overwritten at any time.
.It Dv UFTDIIOC_ERASE_EEPROM Pq Vt 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
.Dv UFTDI_CONFIRM_ERASE
as the argument to this ioctl.
.El
.Sh FILES
.Bl -tag -width "/dev/ttyU*.init" -compact
.It Pa /dev/ttyU*
for callin ports
.It Pa /dev/ttyU*.init
.It Pa /dev/ttyU*.lock
corresponding callin initial-state and lock-state devices
.Pp
.It Pa /dev/cuaU*
for callout ports
.It Pa /dev/cuaU*.init
.It Pa /dev/cuaU*.lock
corresponding callout initial-state and lock-state devices
.El
.Sh SEE ALSO
.Xr cu 1 ,
.Xr tty 4 ,
.Xr ucom 4 ,
.Xr usb 4
.Sh HISTORY
The
.Nm
driver appeared in
.Fx 4.8
from
.Nx 1.5 .