LinuxCNC Integrators Manual Глава IX - Параллельный порт

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LinuxCNC Integrators Manual Глава IX - Параллельный порт

Chapter 9 Parallel Port

9.1 Parport

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.

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.

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 "x" mode allows a more flexible

mode with 8 outputs, and 9 inputs. In other parallel ports, the control group has push-pull drivers

and cannot be used as an input.1

No other combinations are supported, and a port cannot be changed from input to output once the

driver is installed. Figure 9.1 shows two block diagrams, one showing the driver when the data

group is configured for output, and one showing it configured for input. For "x" mode, refer to the

pin listing of "halcmd show pin" for pin direction assignment.

The parport driver can control up to 8 ports (defined by MAX_PORTS in hal_parport.c). The ports

are numbered starting at zero.



loadrt hal_parport cfg="<config-string>"

Using the Port Index

I/O addresses below 16 are treated as port indexes. This is the simplest way to install the parport

driver and cooperates with the Linux parport_pc driver if it is loaded.

1 HAL cannot automatically determine if the "x" 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.

To determine whether your port has "open collector" pins, load hal_parport in "x" mode. With no device attached, HAL

should read the pin as TRUE. Next, insert a 470Ω 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 "x" mode.

The external hardware that drives the control pins should also use open collector gates (e.g., 74LS05).

On some machines, BIOS settings may affect whether "x" mode can be used. "SPP" mode is most most likely to work.


EMC V2.4 Integrator Manual

Chapter 9. Parallel Port

loadrt hal_parport cfg="0"

Will use the address Linux has detected for parport0.

Using the Port Address

The configure string consists of a hex port address, followed by an optional direction, repeated for

each port. The direction is "in", "out", or "x" 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:

loadrt hal_parport cfg="0x278 0x378 in 0x20A0 out"

This example installs drivers for one port at 0x0278, with pins 2-9 as outputs (by default, since

neither "in" nor "out" 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 "well known" address, like 0278 or 0378 which is typically configured

in the system BIOS. The address for a PCI card is usually shown in "lspci -v" in an "I/O ports" line,

or in the kernel message log after executing "sudo modprobe -a parport_pc". There is no default

address; if <config-string> does not contain at least one address, it is an error.



• ( B I T ) parport.<portnum>.pin-<pinnum>-out – Drives a physical output pin.

• ( B I T ) parport.<portnum>.pin-<pinnum>-in – Tracks a physical input pin.

• ( B I T ) parport.<portnum>.pin-<pinnum>-in-not – Tracks a physical input pin, but in-


For each pin, <portnum> is the port number, and <pinnum> is the physical pin number in the 25

pin D-shell connector.

For each physical output pin, the driver creates a single HAL pin, for example

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.

For each physical input pin, the driver creates two HAL pins, for example

and 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 -in HAL pin is TRUE if the physical

pin is high, and FALSE if the physical pin is low. The -in-not 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 "x" mode, pins 1, 14, 16, and 17 are also input pins.



• ( B I T ) parport.<portnum>.pin-<pinnum>-out-invert – Inverts an output pin.

• ( B I T ) parport.<portnum>.pin-<pinnum>-out-reset (only for "out" pins) – TRUE if this pin

should be reset when the -reset function is executed.

• (U32) parport.<portnum>.reset-time – The time (in nanoseconds) between a pin is set by

write and reset by the reset function if it is enabled.

The -invert parameter determines whether an output pin is active high or active low. If -invert

is FALSE, setting the HAL -out pin TRUE drives the physical pin high, and FALSE drives it low. If

-invert is TRUE, then setting the HAL -out pin TRUE will drive the physical pin low.



Figure 9.1: Parport Block Diagram



EMC V2.4 Integrator Manual

Chapter 9. Parallel Port

EMC V2.4 Integrator Manual


Chapter 9. Parallel Port


• ( F U N C T ) parport.<portnum>.read– Reads physical input pins of port <portnum> and up-

dates HAL -in and -in-not pins.

• ( F U N C T ) – Reads physical input pins of all ports and updates HAL -in

and -in-not pins.

• ( F U N C T ) parport.<portnum>.write – Reads HAL -out pins of port <portnum> and updates

that port’s physical output pins.

• ( F U N C T ) parport.write-all – Reads HAL -out pins of all ports and updates all physical

output pins.

• ( F U N C T ) parport.<portnum>.reset – Waits until reset-time has elapsed since the associ-

ated write, then resets pins to values indicated by -out-invert and -out-invert settings.

reset must be later in the same thread as write. If -reset is TRUE, then the reset func-

tion will set the pin to the value of -out-invert. This can be used in conjunction with step-

gen’s doublefreq to produce one step per period. The stepgen stepspace for that pin must be

set to 0 to enable doublefreq.

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 -all function and an individual function at the same time.


Common problems

If loading the module reports

insmod: error inserting ’/home/jepler/emc2/rtlib/hal_parport.ko’:

-1 Device or resource busy

then ensure that the standard kernel module parport_pc is not loaded2 and that no other device

in the system has claimed the I/O ports.

If the module loads but does not appear to function, then the port address is incorrect or the

probe_parport module is required.


Using DoubleStep

To setup DoubleStep on the parallel port you must add the function parport.n.reset after par-

port.n.write and configure stepspace to 0 and the reset time wanted. So that step can be asserted

on every period in HAL and then toggled off by parport after being asserted for time specificed by


For example:

loadrt hal_parport cfg="0x378 out"

setp parport.0.reset-time 5000

loadrt stepgen step_type=0,0,0

addf base-thread

addf stepgen.make-pulses base-thread

addf parport.0.write base-thread

addf parport.0.reset base-thread

2 In the EMC packages for Ubuntu, the file /etc/modprobe.d/emc2 generally prevents parport_pc from being automati-

cally loaded.


EMC V2.4 Integrator Manual

Chapter 9. Parallel Port

addf stepgen.capture-position servo-thread


setp stepgen.0.steplen 1

setp stepgen.0.stepspace 0

9.2 probe_parport

In modern PCs, the parallel port may require plug and play (PNP) configuration before it can be

used. The probe_parport module performs configuration of any PNP ports present, and should be

loaded before hal_parport. On machines without PNP ports, it may be loaded but has no effect.



loadrt probe_parport

loadrt hal_parport ...

If the Linux kernel prints a message similar to

parport: PnPBIOS parport detected.

when the parport_pc module is loaded (sudo modprobe -a parport_pc; sudo rmmod parport_pc)

then use of this module is probably required.

Оглавление книги LinuxCNC Integrators Manual

Глава Название
Глава 1 LinuxCNC Integrators Manual Глава I - Важные определения
Глава 2 LinuxCNC Integrators Manual Глава II - Аппаратное обеспечение (Hardware)
Глава 3 LinuxCNC Integrators Manual Глава III - Конфигурационные файлы
Глава 4 Доделать! LinuxCNC Integrators Manual Глава IV - Файл INI
Глава 5 Доделать! LinuxCNC Integrators Manual Глава V - LinuxCNC и HAL
Глава 6 Доделать! LinuxCNC Integrators Manual Глава VI - Основы HAL
Глава 7 Доделать! LinuxCNC Integrators Manual Глава VII - Настройка шаговых двигателей
Глава 8 Доделать! LinuxCNC Integrators Manual Глава VIII - Компонетны HAL
Глава 9 Забыли перевести! LinuxCNC Integrators Manual Глава IX - Параллельный порт
Глава 10 Доделать! LinuxCNC Integrators Manual Глава X - Пользовательский интерфейс HAL (Halui)
Глава 11 Доделать! LinuxCNC Integrators Manual Глава XI - Примеры HAL
Глава 12 Доделать! LinuxCNC Integrators Manual Глава XII - Virtual Control Panel - Виртуальная панель управления