Forth Lesson 22: Difference between revisions

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(Describe some canned commands)
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=== On XO-1.75 ===
=== On XO-1.75 ===


Get http://dev.laptop.org/~wmb/armforth, http://dev.laptop.org/~wmb/armtools.dic, and http://dev.laptop.org/~wmb/mmap.fth . Copy them into your home directory on an XO-1.75 .
Get http://dev.laptop.org/~wmb/sdkit-arm.tgz . Unpack it into your home directory on an XO-1.75 .


$ tar xfz sdkit-arm.tgz
Then do:


Then:

$ cd sdkit-arm
$ sudo -s
$ sudo -s
# ./sdkit.sh
# ./armforth armtools.dic mmap.fth -
ok
ok


sdkit comes up in hex mode, so you can enter and display numbers in hex without additional qualifiers. To enter a decimal number, precede it with "d# ", e.g. "d# 123"
Now you can use mmap to get access to I/O devices.

==== GPIO Access ====

{| class="wikitable"
|-
! Command
! Stack
! Description
! Example
|-
| gpio-pin@
| ( gpio# -- flag )
| Flag is true if GPIO pin is high
| d# 108 gpio-pin@ .
|-
| gpio-out?
| ( gpio# -- flag )
| Flag is true if GPIO is an output
| d# 108 gpio-out? .
|-
| gpio-set
| ( gpio# -- )
| Drives GPIO high
| d# 108 gpio-set
|-
| gpio-clr
| ( gpio# -- )
| Drives GPIO low
| d# 108 gpio-clr
|-
| gpio-rise@
| ( gpio# -- flag )
| Flag is true if rising edge detected
| d# 108 gpio-rise@ .
|-
| gpio-fall@
| ( gpio# -- flag )
| Flag is true if falling edge detected
| d# 108 gpio-fall@ .
|-
| gpio-edge@
| ( gpio# -- flag )
| Flag is true if edge detected
| d# 108 gpio-edge@ .
|-
| gpio-clr-edge
| ( gpio# -- )
| Clears GPIO edge detector
| d# 108 gpio-clr-edge
|-
| gpio-dir-out
| ( gpio# -- )
| Sets GPIO direction to output
| d# 108 gpio-dir-out
|-
| gpio-dir-in
| ( gpio# -- )
| Sets GPIO direction to input
| d# 108 gpio-dir-out
|-
| gpio-set-rer
| ( gpio# -- )
| Enables rising edge detection
| d# 108 gpio-set-rer
|-
| gpio-clr-rer
| ( gpio# -- )
| Disables rising edge detection
| d# 108 gpio-set-rer
|-
| gpio-set-fer
| ( gpio# -- )
| Enables falling edge detection
| d# 108 gpio-set-fer
|-
| gpio-clr-fer
| ( gpio# -- )
| Disables falling edge detection
| d# 108 gpio-set-fer
|}

==== Multi-Function Pin Register Access ====

The Multi-Function Pin Registers (MFPRs) control the assignment of chip pins to internal functions, and also control characteristics of those pins, such as drive strength, pull up/down resistors, etc. Since each multi-function pins can be used as a GPIO, we use the GPIO number to designate which pin we are interested in.

{| class="wikitable"
|-
! Command
! Stack
! Description
! Example
|-
| af@
| ( gpio# -- function )
| Returns the MFPR setting for gpio#
| d# 108 af@ .
|-
| af!
| ( function gpio# -- )
| Sets the MFPR for gpio#
| h# a0c0 d# 108 af!
|-
| dump-mprs
| ( -- )
| Displays a table of all MFPR settings
| dump-mfprs
|-
| gpio>mfpr
| ( gpio# -- address )
| Returns the address of the MFPR register for gpio#
| d# 108 gpio>mfpr .
|}

==== Accessing Arbitrary Devices ====

In addition to the "canned" access words for specific devices, you can manually access any device you wish, using the "mmap" command to assign a virtual address to the I/O device's physical address.

{| class="wikitable"
|-
! Command
! Stack
! Description
! Example
|-
| mmap
| ( phys-address size -- virt-address )
| Assigns a virtual address to a physical device address
| d4050000 1000 mmap constant clock-unit-base
|}


The physical address and size must both be multiples of 0x1000, i.e. their low three hex digits must be 0.
ok hex
ok d4019000 1000 mmap constant gpio-base
ok gpio-base 154 + l@ .


You can add offsets to the virtual address to access registers within the range {virtual-address .. virtual-address+size-1}. For example:
For pinmux (MFPR) access:


ok d401e000 1000 mmap constant mfpr-base
ok d4050000 1000 mmap constant clock-unit
ok mfpr-base 2b8 + l@ .
ok clock-unit 24 + l@ .

Revision as of 20:55, 20 May 2011

Mitch Bradley's Forth and
Open Firmware Lessons:

Using Forth Under Linux

You can run Forth under Linux and use it to inspect I/O devices.

On XO-1.75

Get http://dev.laptop.org/~wmb/sdkit-arm.tgz . Unpack it into your home directory on an XO-1.75 . 

 $ tar xfz sdkit-arm.tgz

Then: 

 $ cd sdkit-arm
 $ sudo -s
 # ./sdkit.sh
 ok

sdkit comes up in hex mode, so you can enter and display numbers in hex without additional qualifiers. To enter a decimal number, precede it with "d# ", e.g. "d# 123"

GPIO Access

Command Stack Description Example
gpio-pin@ ( gpio# -- flag ) Flag is true if GPIO pin is high d# 108 gpio-pin@ .
gpio-out? ( gpio# -- flag ) Flag is true if GPIO is an output d# 108 gpio-out? .
gpio-set ( gpio# -- ) Drives GPIO high d# 108 gpio-set
gpio-clr ( gpio# -- ) Drives GPIO low d# 108 gpio-clr
gpio-rise@ ( gpio# -- flag ) Flag is true if rising edge detected d# 108 gpio-rise@ .
gpio-fall@ ( gpio# -- flag ) Flag is true if falling edge detected d# 108 gpio-fall@ .
gpio-edge@ ( gpio# -- flag ) Flag is true if edge detected d# 108 gpio-edge@ .
gpio-clr-edge ( gpio# -- ) Clears GPIO edge detector d# 108 gpio-clr-edge
gpio-dir-out ( gpio# -- ) Sets GPIO direction to output d# 108 gpio-dir-out
gpio-dir-in ( gpio# -- ) Sets GPIO direction to input d# 108 gpio-dir-out
gpio-set-rer ( gpio# -- ) Enables rising edge detection d# 108 gpio-set-rer
gpio-clr-rer ( gpio# -- ) Disables rising edge detection d# 108 gpio-set-rer
gpio-set-fer ( gpio# -- ) Enables falling edge detection d# 108 gpio-set-fer
gpio-clr-fer ( gpio# -- ) Disables falling edge detection d# 108 gpio-set-fer

Multi-Function Pin Register Access

The Multi-Function Pin Registers (MFPRs) control the assignment of chip pins to internal functions, and also control characteristics of those pins, such as drive strength, pull up/down resistors, etc. Since each multi-function pins can be used as a GPIO, we use the GPIO number to designate which pin we are interested in.

Command Stack Description Example
af@ ( gpio# -- function ) Returns the MFPR setting for gpio# d# 108 af@ .
af! ( function gpio# -- ) Sets the MFPR for gpio# h# a0c0 d# 108 af!
dump-mprs ( -- ) Displays a table of all MFPR settings dump-mfprs
gpio>mfpr ( gpio# -- address ) Returns the address of the MFPR register for gpio# d# 108 gpio>mfpr .

Accessing Arbitrary Devices

In addition to the "canned" access words for specific devices, you can manually access any device you wish, using the "mmap" command to assign a virtual address to the I/O device's physical address.

Command Stack Description Example
mmap ( phys-address size -- virt-address ) Assigns a virtual address to a physical device address d4050000 1000 mmap constant clock-unit-base

The physical address and size must both be multiples of 0x1000, i.e. their low three hex digits must be 0.

You can add offsets to the virtual address to access registers within the range {virtual-address .. virtual-address+size-1}. For example: 

 ok d4050000 1000 mmap  constant clock-unit
 ok clock-unit 24 + l@ .
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