drivers.lyx

CNC 的开放码,EMC2 V2.2.8版

#LyX 1.3 created this file. For more info see http://www.lyx.org/
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\layout Chapter

Hardware Drivers
\layout Section


\begin_inset LatexCommand \label{sec:Parport}

\end_inset 

Parport
\begin_inset LatexCommand \index{parallel port}

\end_inset 


\layout Standard

Parport is a driver for the traditional PC parallel port.
 The port has a total of 17 physical pins.
 The original parallel port divided those pins into three groups: data,
 control, and status.
 The data group consists of 8 output pins, the control group consists of
 4 pins, and the status group consists of 5 input pins.
\layout Standard

In the early 1990's, the bidirectional parallel port was introduced, which
 allows the data group to be used for output or input.
 The HAL driver supports the bidirectional port, and allows the user to
 set the data group as either input or output.
 If configured as output, a port provides a total of 12 outputs and 5 inputs.
 If configured as input, it provides 4 outputs and 13 inputs.
 
\layout Standard

In some parallel ports, the control group pins are open collectors, which
 may also be driven low by an external gate.
 On a board with open collector control pins, the 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode allows a more flexible mode with 8 dedicated outputs, 5 dedicated
 inputs, and 4 open collector pins.
 In other parallel ports, the control group has push-pull drivers and cannot
 be used as an input.
\begin_inset Foot
collapsed false

\layout Standard

HAL cannot automatically determine if the 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode bidirectional pins are actually open collectors (OC).
 If they are not, they cannot be used as inputs, and attempting to drive
 them LOW from an external source can damage the hardware.
\layout Standard

To determine whether your port has 
\begin_inset Quotes eld
\end_inset 

open collector
\begin_inset Quotes erd
\end_inset 

 pins, load hal_parport in 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode, output a HIGH value on the pin.
 HAL should read the pin as TRUE.
 Next, insert a 470
\begin_inset Formula $\Omega$
\end_inset 

 resistor from one of the control pins to GND.
 If the resulting voltage on the control pin is close to 0V, and HAL now
 reads the pin as FALSE, then you have an OC port.
 If the resulting voltage is far from 0V, or HAL does not read the pin as
 FALSE, then your port cannot be used in 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode.
\layout Standard

The external hardware that drives the control pins should also use open
 collector gates (e.g., 74LS05).
 Generally, the -out HAL pins should be set to TRUE when the physical pin
 is being used as an input.
\layout Standard

On some machines, BIOS settings may affect whether 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode can be used.
 
\begin_inset Quotes eld
\end_inset 

SPP
\begin_inset Quotes erd
\end_inset 

 mode is most most likely to work.
\end_inset 


\layout Standard

No other combinations are supported, and a port cannot be changed from input
 to output once the driver is installed.
 Figure 
\begin_inset LatexCommand \ref{fig:Parport-block-diag}

\end_inset 

 shows two block diagrams, one showing the driver when the data group is
 configured for output, and one showing it configured for input.
\layout Standard

The parport driver can control up to 8 ports (defined by MAX_PORTS in hal_parpor
t.c).
 The ports are numbered starting at zero.
\layout Subsection

Installing
\layout LyX-Code

loadrt hal_parport cfg="<config-string>"
\layout Standard

The config string consists of a hex port address, followed by an optional
 direction, repeated for each port.
 The direction is 
\begin_inset Quotes eld
\end_inset 

in
\begin_inset Quotes erd
\end_inset 

, 
\begin_inset Quotes eld
\end_inset 

out
\begin_inset Quotes erd
\end_inset 

, or 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 and determines the direction of the physical pins 2 through 9, and whether
 to create input HAL pins for the physical control pins.
 If the direction is not specified, the data group defaults to output.
 For example:
\layout LyX-Code

loadrt hal_parport cfg="0x278 0x378 in 0x20A0 out"
\layout Standard

This example installs drivers for one port at 0x0278, with pins 2-9 as outputs
 (by default, since neither 
\begin_inset Quotes eld
\end_inset 

in
\begin_inset Quotes erd
\end_inset 

 nor 
\begin_inset Quotes eld
\end_inset 

out
\begin_inset Quotes erd
\end_inset 

 was specified), one at 0x0378, with pins 2-9 as inputs, and one at 0x20A0,
 with pins 2-9 explicitly specified as outputs.
 Note that you must know the base address of the parallel port to properly
 configure the driver.
 For ISA bus ports, this is usually not a problem, since the port is almost
 always at a 
\begin_inset Quotes eld
\end_inset 

well known
\begin_inset Quotes erd
\end_inset 

 address, like 0278 or 0378 which is typically configured in the system
 BIOS.
 The address for a PCI card is usally shown in 
\begin_inset Quotes eld
\end_inset 

lspci -v
\begin_inset Quotes erd
\end_inset 

 in an 
\begin_inset Quotes eld
\end_inset 

I/O ports
\begin_inset Quotes erd
\end_inset 

 line, or in the kernel message log after executing 
\family typewriter 

\begin_inset Quotes eld
\end_inset 

sudo modprobe -a parport_pc
\family default 

\begin_inset Quotes erd
\end_inset 

.
 There is no default address; if 
\family typewriter 
<config-string>
\family default 
 does not contain at least one address, it is an error.
\layout Standard


\begin_inset Float figure
wide false
collapsed false

\layout Standard
\align center 

\begin_inset Graphics
	filename parport-block-diag.eps
	width 8in
	height 10in
	keepAspectRatio
	rotateAngle 90
	rotateOrigin center

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{fig:Parport-block-diag}

\end_inset 

Parport Block Diagram
\end_inset 


\layout Subsection

Pins
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
parport.<portnum>.pin-<pinnum>-out
\family default 
 -- Drives a physical output pin.
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
parport.<portnum>.pin-<pinnum>-in
\family default 
 -- Tracks a physical input pin.
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
parport.<portnum>.pin-<pinnum>-in-not
\family default 
 -- Tracks a physical input pin, but inverted.
\layout Standard

For each pin, 
\family typewriter 
<portnum>
\family default 
 is the port number, and 
\family typewriter 
<pinnum>
\family default 
 is the physical pin number in the 25 pin D-shell connector.
\layout Standard

For each physical output pin, the driver creates a single HAL pin, for example
 
\family typewriter 
parport.0.pin-14-out
\family default 
.
 Pins 2 through 9 are part of the data group and are output pins if the
 port is defined as an output port.
 (Output is the default.) Pins 1, 14, 16, and 17 are outputs in all modes.
 These HAL pins control the state of the corresponding physical pins.
\layout Standard

For each physical input pin, the driver creates two HAL pins, for example
 
\family typewriter 
parport.0.pin-12-in
\family default 
 and 
\family typewriter 
parport.0.pin-12-in-not
\family default 
.
 Pins 10, 11, 12, 13, and 15 are always input pins.
 Pins 2 through 9 are input pins only if the port is defined as an input
 port.
 The 
\family typewriter 
-in
\family default 
 HAL pin is TRUE if the physical pin is high, and FALSE if the physical
 pin is low.
 The 
\family typewriter 
-in-not
\family default 
 HAL pin is inverted -- it is FALSE if the physical pin is high.
 By connecting a signal to one or the other, the user can determine the
 state of the input.
 In 
\begin_inset Quotes eld
\end_inset 

x
\begin_inset Quotes erd
\end_inset 

 mode, pins 1, 14, 16, and 17 are also input pins.
\layout Subsection

Parameters
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
parport.<portnum>.pin-<pinnum>-out-invert
\family default 
 -- Inverts an output pin.
\layout Itemize


\family typewriter 
\noun on 
(bit) 
\noun default 
parport.<portnum>.pin-<pinnum>-out-reset 
\family default 
(only for pins 2..9) -- TRUE if this pin should be reset when the 
\family typewriter 
-reset
\family default 
 function is executed.
\layout Itemize


\family typewriter 
(U32) parport.<portnum>.reset-time
\family default 
 -- The time (in nanoseconds) between a pin is set by 
\family typewriter 
write
\family default 
 and reset by 
\family typewriter 
reset
\family default 
 HAL functions.
\layout Standard

The 
\family typewriter 
-invert
\family default 
 parameter determines whether an output pin is active high or active low.
 If 
\family typewriter 
-invert
\family default 
 is FALSE, setting the HAL 
\family typewriter 
-out
\family default 
 pin TRUE drives the physical pin high, and FALSE drives it low.
 If 
\family typewriter 
-invert
\family default 
 is TRUE, then setting the HAL 
\family typewriter 
-out
\family default 
 pin TRUE will drive the physical pin low.
\layout Standard

If 
\family typewriter 
-reset
\family default 
 is TRUE, then the 
\family typewriter 
reset
\family default 
 function will set the pin to the value of 
\family typewriter 
-out-invert
\family default 
.
 This can be used in conjunction with stepgen's 
\family typewriter 
doublefreq
\family default 
 to produce one step per period.
\layout Subsection

Functions
\layout Itemize


\family typewriter 
\noun on 
(funct) 
\noun default 
parport.<portnum>.read
\family default 
-- Reads physical input pins of port 
\family typewriter 
<portnum>
\family default 
 and updates HAL 
\family typewriter 
-in
\family default 
 and 
\family typewriter 
-in-not
\family default 
 pins.
\layout Itemize


\family typewriter 
\noun on 
(funct) 
\noun default 
parport.read-all
\family default 
 -- Reads physical input pins of all ports and updates HAL 
\family typewriter 
-in
\family default 
 and 
\family typewriter 
-in-not
\family default 
 pins.
\layout Itemize


\family typewriter 
\noun on 
(funct) 
\noun default 
parport.<portnum>.write
\family default 
 -- Reads HAL 
\family typewriter 
-out
\family default 
 pins of port 
\family typewriter 
<portnum>
\family default 
 and updates that port's physical output pins.
\layout Itemize


\family typewriter 
\noun on 
(funct) 
\noun default 
parport.write-all
\family default 
 -- Reads HAL 
\family typewriter 
-out
\family default 
 pins of all ports and updates all physical output pins.
\layout Itemize


\family typewriter 
\noun on 
(funct) 
\noun default 
parport.<portnum>.reset
\family default 
 -- Waits until 
\family typewriter 
reset-time
\family default 
 has elapsed since the associated 
\family typewriter 
write
\family default 
, then resets pins to values indicated by 
\family typewriter 
-out-invert
\family default 
 and 
\family typewriter 
-out-invert
\family default 
 settings.
 
\family typewriter 
reset
\family default 
 must be later in the same thread as 
\family typewriter 
write
\layout Standard

The individual functions are provided for situations where one port needs
 to be updated in a very fast thread, but other ports can be updated in
 a slower thread to save CPU time.
 It is probably not a good idea to use both an 
\family typewriter 
-all
\family default 
 function and an individual function at the same time.
\layout Subsection

Common problems
\layout Standard

If loading the module reports
\layout LyX-Code

insmod: error inserting '/home/jepler/emc2/rtlib/hal_parport.ko':
\newline 
-1 Device or resource busy 
\layout Standard

then ensure that the standard kernel module 
\family typewriter 
parport_pc
\family default 
 is not loaded
\begin_inset Foot
collapsed false

\layout Standard

In the emc packages for Ubuntu, the file /etc/modprobe.d/emc2 generally prevents
 
\family typewriter 
parport_pc
\family default 
 from being automatically loaded.
\end_inset 

 and that no other device in the system has claimed the I/O ports.
\layout Standard

If the module loads but does not appear to function, then the port address
 is incorrect or the 
\family typewriter 
probe_parport
\family default 
 module is required.