NAME

LCD - LCD controller

SYNOPSIS

1-wire LCD controller by Louis Swart

FAMILY CODE

SPECIAL PROPERTIES

backlight

write-only,yes-no
Write a non-zero value to turn on the LCD backlight. Write zero to turn off.

counters[0-3,ALL]

read-only,unsigned integer
Read the number of times the gpio has been externally changed. If wired to a push switch, will count twice per button press. The LCD firmware resets all the counter when any one is read. Use the ALL extension to read them all, simultaneously, or use the cumulative property instead.
ALL is an aggregate of the properties, comma separated. Read atomically.

cumulative[0-3,ALL]

read-write,unsigned integer
Cumulative sum of the counters property. To reset, write a zero. The cumulative counter can have any value written, which allows preservation of counts across program restarts if the value at program termination is stored.
Reading cumulative will reset the counters property. All the cumulative counters will be updated so that no counts will be lost. Reads of counters can be interspersed without losing cumulative accuracy.
Note: cumulative requires the caching system be compiled into libow.
ALL is an aggregate of the properties, comma separated.

data

read-write,unsigned int
Contents of the LCD data byte (see datasheet). Not usually needed.

LCDon

write-only,yes-no
Write a non-zero value to turn on the LCD screen (also clears). Write a zero to turn off.

line16[0-3,ALL] line20[0-3,ALL] line40[0-1,ALL]

write-only,ascii
Write text to the LCD screen. Assumes 16/20/40 char width. (Cannot be determined from controller).
ALL is an aggregate of the properties, comma separated. Each is set in turn.

memory

read-write,binary
112 bytes of on-board memory.

register

read-write,unsigned int
Contents of the LCD register (see datasheet). Not usually needed.

screen16 screen20 screen40

write-only,ascii
Write text to the LCD screen. Assumes 16/20/40 char width. (Cannot be determined from controller).

version

read-only,ascii
Self-reported LCD controller version. 16 bytes.

STANDARD PROPERTIES

address

r_address

read-only, ascii
The entire 64-bit unique ID. Given as upper case hexadecimal digits (0-9A-F).
address starts with the family code
r address is the address in reverse order, which is often used in other applications and labeling.

crc8

read-only, ascii
The 8-bit error correction portion. Uses cyclic redundancy check. Computed from the preceding 56 bits of the unique ID number. Given as upper case hexadecimal digits (0-9A-F).

family

read-only, ascii
The 8-bit family code. Unique to each type of device. Given as upper case hexadecimal digits (0-9A-F).

id

r_id

read-only, ascii
The 48-bit middle portion of the unique ID number. Does not include the family code or CRC. Given as upper case hexadecimal digits (0-9A-F).
r id is the id in reverse order, which is often used in other applications and labeling.

locator

r_locator

read-only, ascii
Uses an extension of the 1-wire design from iButtonLink company that associated 1-wire physical connections with a unique 1-wire code. If the connection is behind a Link Locator the locator will show a unique 8-byte number (16 character hexadecimal) starting with family code FE.
If no Link Locator is between the device and the master, the locator field will be all FF.
r locator is the locator in reverse order.

present (DEPRECATED)

read-only, yes-no
Is the device currently present on the 1-wire bus?

type

read-only, ascii
Part name assigned by Dallas Semi. E.g. DS2401 Alternative packaging (iButton vs chip) will not be distiguished.

ALARMS

None implemented.

DESCRIPTION

1-Wire

1-wire is a wiring protocol and series of devices designed and manufactured by Dallas Semiconductor, Inc. The bus is a low-power low-speed low-connector scheme where the data line can also provide power.

Each device is uniquely and unalterably numbered during manufacture. There are a wide variety of devices, including memory, sensors (humidity, temperature, voltage, contact, current), switches, timers and data loggers. More complex devices (like thermocouple sensors) can be built with these basic devices. There are also 1-wire devices that have encryption included.

The 1-wire scheme uses a single bus master and multiple slaves on the same wire. The bus master initiates all communication. The slaves can be individually discovered and addressed using their unique ID.

Bus masters come in a variety of configurations including serial, parallel, i2c, network or USB adapters.

OWFS design

OWFS is a suite of programs that designed to make the 1-wire bus and its devices easily accessible. The underlying principle is to create a virtual filesystem, with the unique ID being the directory, and the individual properties of the device are represented as simple files that can be read and written.

Details of the individual slave or master design are hidden behind a consistent interface. The goal is to provide an easy set of tools for a software designer to create monitoring or control applications. There are some performance enhancements in the implementation, including data caching, parallel access to bus masters, and aggregation of device communication. Still the fundamental goal has been ease of use, flexibility and correctness rather than speed.

LCD

The LCD (3) controller is a microprocessor driven device that simulates the operation of 1-wire devices. It's creator has arbitrarily chosen the family code FF. The controller requires external power. Full details are available from the designer.
The main draw of the LCD controller is as any easy way to provide output to users.

ADDRESSING

All 1-wire devices are factory assigned a unique 64-bit address. This address is of the form:

Family Code: 8 bits
Address: 48 bits
CRC: 8 bits

Addressing under OWFS is in hexadecimal, of form:

: 01.123456789ABC

where 01 is an example 8-bit family code, and 12345678ABC is an example 48 bit address.

The dot is optional, and the CRC code can included. If included, it must be correct.

DATASHEET

Available from http://www.louisswart.co.za/1-Wire_index.html

AVAILABILITY

http://www.owfs.org

AUTHOR

Paul Alfille (paul.alfille@gmail.com)