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.\"  -*- nroff -*-
.\"  $Id: set_ftdi_lat.1 321 2010-08-01 19:43:39Z mueller $
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.\" Copyright 2010- by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
.\" 
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.
.TH SET_FTDI_LAT 1 2010-07-24 "Retro Project" "Retro Project Manual"
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.SH NAME
set_ftdi_lat \- set latency timer in FTDI USB UART or FIFO
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.SH SYNOPSIS
.
.SY set_ftdi_lat
.RI [ dev ]
.RI [ time ]
.YS
.
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.SH DESCRIPTION
FTDI USB UART or FIFO adapters of type FT232, FT245, and other similar
models have a latency timer which controls the maximal time between reception
of a byte by the UART or FIFO and the emission of a USB frame. The default
is 16 msec and can lead to unsatisfactory response times.
The 
.B set_ftdi_lat
script allows to set this latency timer via a node in the
.I /sys
virtual file system, specifically
.IP "" 4
.I /sys/bus/usb-serial/devices/ttyUSBn/latency_timer
.
.PP
The first optional argument
.I dev
allows to specify the device name in the form
.I USBn
with the default
.IR USB0 .
The second optional argument
.I
time
allows to specify the new value of the latency timer, given in msec. 
Default is 1 msec.
.
.
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.SH EXIT STATUS
If device
.RI tty dev
is not found or the entry in
.I /sys
is not writable an exit status 1 is returned.

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.SH EXAMPLES
In general the command is given via 
.BR sudo ,
like
.EX
    sudo set_ftdi_lat USB0 1
.EE
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.SH "SEE ALSO"
.BR sudo (1)
.
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.SH AUTHOR
Walter F.J. Mueller <W.F.J.Mueller@gsi.de>