CFA633-RDI-KS datasheet(47/88 Pages) CRYSTAIFONTZ

47 / 88 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KS LCD Module (Hardware v2.0 / Firmware s2v1)

February 2012

Page 47

18 (0x12): Read DOW Device Information

When power is applied to the CFA633, it detects any devices (WR-DOW-Y17 temperature sensors) connected to the

Dallas Semiconductor One-Wire (DOW) bus and stores the device’s information. This command will allow the host to

read the device’s information.

The first byte returned is the Family Code of the Dallas One-Wire / iButton device. There is a list of the possible Dallas

One-Wire / iButton device family codes available in App Note 155: 1-Wire Software Resource Guide on the Maxim/Dallas

website.

type: 0x12 = 1810

valid data_length is 1

data[0] = device index (0-31 valid)

The return packet will be:

type: 0x40 | 0x12 = 0x52 = 8210

data_length = 9

data[0] = device index (0-31 valid)

data[1-8] = ROM ID of the device

If data[1] is 0x22 (DS1822 Econo One-Wire Digital Thermometer temperature sensor) or 0x28 (DS18B20 High Precision

One-Wire Digital Thermometer temperature sensor used on our WR-DOW-Y17), then that device can be set up to

automatically convert and report the temperature every second. See the command 19 (0x13): Set Up Temperature

Reporting (Pg. 48).

NOTE ON COMMAND 18: READ DOW DEVICE INFORMATION

The GPIO pin used for DOW must not be configured as user GPIO. It must be configured to its default

drive mode in order for the DOW functions to work correctly.

These settings are factory default but may be changed by the user. Please see command 34 (0x22):

Set or Set and Configure GPIO Pins (Pg. 58).

In order for the DOW subsystem to be enabled and operate correctly, user GPIO[4] must be configured

as:

DDD = "111: 1=Hi-Z, 0=Slow, Strong Drive Down".

F = "0: Port unused for user GPIO."

This state is the factory default, but it can be changed and saved by the user. To ensure that GPIO[4] is

set correctly and the DOW operation is enabled, send the following command:

command = 34

length = 3

data[0] = 4

data[1] = 100

data[2] = 7

This setting must be saved as the boot state, so when the CFA633 reboots it will detect the DOW

devices.

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