AN10397,AN10397 pdf中文资料,AN10397引脚图,AN10397电路-Datasheet-电子工程世界

AN10397

How to use the SC18IM700 to control any I

2

C-bus device

Rev. 01 — 5 December 2005

Application note

Document information

Info

Keywords

Abstract

Content

I2C, I2C controller, Master I2C, UART

This application note shows how the SC18IM700 can be used in a system

to control other I

2

C-bus slave devices.

Philips Semiconductors

AN10397

How to use the SC18IM700 to control any I

2

C-bus device

Revision history

Rev

01

Date

20051205

Description

Application note; initial version.

Contact information

For additional information, please visit:

http://www.semiconductors.philips.com

For sales office addresses, please send an email to:

sales.addresses@www.semiconductors.philips.com

AN10397_1

Application note

Rev. 01 — 5 December 2005

2 of 10

Philips Semiconductors

AN10397

How to use the SC18IM700 to control any I

2

C-bus device

1. Introduction

Philips Semiconductors recently introduced a whole new family of devices called

‘the Bridges’. These devices are intended to transform data from one serial bus to another

serial bus, and this transformation allows the host to control devices that have serial host

bus interfaces that are not native to the system.

One such scenario is the I

2

C-bus interface. There are wide ranges of devices that have an

I

2

C-bus interface to communicate with a host. Some of such devices are: EEPROMs,

temperature sensors, analog-to-digital or digital-to-analog converters, LED blinkers and

I/O expanders. To use these devices in the system, a host must have an integrated

I

2

C-bus controller on-board, or it must have an external, stand-alone I

2

C-bus controller.

Philips Semiconductors’ SC18IM700—an I

2

C-bus controller with a UART host interface—

is the perfect choice in the case where the host does not have an integrated I

2

C-bus

controller on-board, and the system designer wishes to use I

2

C-bus related devices in the

system. The SC18IM700 does not require any programming at all other than the code to

write and read from the host’s UART port. This non-programming is possible because

SC18IM700 communicates with the host through a series of messages that are based on

ASCII characters.

This application note shows how a host can control, setup, read and write to any I

2

C-bus

devices through this UART-to-I

2

C controller. The examples used in this application note

are built around an LED blinker from Philips Semiconductors, the PCA9531. Besides the

I

2

C-bus control function, the SC18IM700 also contains a general-purpose 8-bit

programmable I/O port. These eight general purpose I/O pins can be configured to the

following modes: input only, open-drain output, push-pull output or quasi-bidirectional

input/output.

2. PCA9531: LED blinker

The PCA9531 is an 8-bit I

2

C-bus and SMBus I/O expander optimized for dimming LEDs in

256 discrete steps for Red/Green/Blue (RGB) color mixing and backlight applications.

The initial setup sequence programs the two blink rates and duty cycles for each individual

PWM. From then on, only one command from the bus master is required to turn individual

LEDs ON, OFF, BLINK RATE 1 or BLINK RATE 2. Based on the programmed frequency

and duty cycle, BLINK RATE 1 and BLINK RATE 2 will cause the LEDs to appear at a

different brightness or blink at periods up to 1.69 second. The open-drain outputs directly

drive the LEDs with maximum output sink current of 25 mA per bit and 100 mA per

package.

Please refer to the PCA9531 data sheet for more detail about this device and its internal

registers’ usage. The following steps to program the part are extracted from the example

in the data sheet, page 11.

AN10397_1

Application note

Rev. 01 — 5 December 2005

3 of 10

Philips Semiconductors

AN10397

How to use the SC18IM700 to control any I

2

C-bus device

2.1 Programming example

The following example will show how to set LED0 to LED3 on. It will then set LED4 and

LED5 to blink at 1 Hz at a 50 % duty cycle. LED6 and LED7 will be set to be dimmed at

25 % of their maximum brightness (duty cycle = 25 %).

Table 1:

START

PCA9531 address with A0, A1, A2 = LOW

PSC0 subaddress + auto-increment

Set prescaler PSC0 to achieve a period of 1 second:

blink period =

1

= PSC0 +

1

----------------------

-

152

PSC0 = 151

Set PWM0 duty cycle to 50 %:

PWM0

----------------

=

0.5

-

256

PWM0 = 128

Set prescaler PCS1 to dim at maximum frequency:

blink period =

max

PSC1 = 0

Set PWM1 output duty cycle to 25 %:

PWM1 =

0.25

----------------

-

256

PWM1 = 64

Set LED0 to LED3 on

Set LED4, LED5 to PWM0, and LED6, LED7 to PWM1

STOP

[1]

PCA9531 programming example

I

2

C-bus data

[1]

S

C0h

11h

97h

Programming step

80h

00h

40h

55h

FAh

P

This column shows the steps needed to be performed by the host to set the LED to blink at a specified rate.

AN10397_1

Application note

Rev. 01 — 5 December 2005

4 of 10

Philips Semiconductors

AN10397

How to use the SC18IM700 to control any I

2

C-bus device

3. SC18IM700: UART to I

2

C-bus controller

The SC18IM700 is designed to serve as an interface between a standard UART of a

microcontroller/microprocessor and the serial I

2

C-bus. This allows the

microcontroller/microprocessor to communicate directly with other I

2

C-bus devices. The

SC18IM700 can operate as an I

2

C-bus master and can be a transmitter or a receiver. The

SC18IM700 controls all the I

2

C-bus specific sequences, protocol, arbitration and timing.

The host communicates with the SC18IM700 with ASCII messages protocol; this makes

the control sequences from host to SC18IM700 become very simple.

The host initiates I

2

C-bus data transfer, read from and write to SC18IM700 internal

registers through a series of ASCII commands. Table 2 lists the ASCII commands

supported by SC18IM700, and also their hex value representation. Unrecognized

commands are ignored by the device.

Table 2:

S

P

R

W

I

O

Z

ASCII commands supported by the SC18IM700

Hex value

0x53

0x50

0x52

0x57

0x49

0x4F

0x5A

Command function

I

2

C-bus START command

I

2

C-bus STOP command

read SC18IM700 internal register command

write to SC18IM700 internal register command

read GPIO port command

write to GPIO port command

power-down

ASCII command

Please refer to the SC18IM700 data sheet for more descriptive detail of the above

commands.

4. Using the SC18IM700 to control the PCA9531

HOST

TX

RX

SC18IM700

UART

I

2

C-BUS

MASTER

SDA

SCL

PCA9531

UART

002aab967

Fig 1. SC18IM700 controlling the PCA9531

The ‘S’ command can be used to setup the PCA9531’s internal registers to blink the LED

at specified frequency and rate. The format for the ‘S’ command is shown in

Figure 2.

S CHAR.

SLAVE ADR.

+W

NUMBER

OF BYTES

DATA 0

DATA N

P CHAR.

Fig 2. ‘S’ command format

AN10397_1

Application note

Rev. 01 — 5 December 2005

5 of 10

AN10397

AN10397概述

文档预览

推荐资源