AN4099 datasheet(28/39 Pages) STMICROELECTRONICS

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Infrared receiver

AN4099

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Doc ID 023110 Rev 2

3.4.2

SIRC library

SIRC_Init()

This function initializes the different peripherals used for the SIRC protocol.

SIRC_Decode (SIRC_Frame_TypeDef *sirc_frame)

This function is intended to be called in the user application. It decodes the SIRC

received messages. It has as a parameter a structure that contains the different values

of the IR frame.

typedef struct

{

__IO uint8_t Command;

/* Command field

__IO uint8_t Address;

/* Address field

} SIRC_Frame_TypeDef;

SIRC_decode () must be executed when the IRFrameReceived flag is equal to YES.

SIRC_ResetPacket()

This function puts the IR packet to the default state. This function is called in the

TIM2_IRQHandler routine. It occurs each timer overflow to reset the IR packet.

SIRC_DeInit()

This function de-initializes the different peripherals used for the SIRC protocol.

TIM2_IRQHandler ()

This function handles the TIM Capture Compare interrupt.

–

Timer Falling Edge Event: this is used to measure the different periods between

two successive falling edges in order to identify the frame bits.

–

Timer Rising Edge Event: this is used to measure the duration between falling

and rising edges (low pulse duration).

–

Update event (time-out event): this resets the RC5 packet. The timer overflow is

set to 4 ms.

The bit value is determined from these two durations.

3.4.3

How to use the SIRC decoder driver

To use the SIRC decoder driver, proceed as follows.

–

TIM2 Capture Compare and Update interrupts are used to decode the IR frame. If

a frame is received correctly a global variable "IRFrameReceived" is set to inform

the application.

–

The application should then call the function SIRC_Decode() to retrieve the

received IR frame.

–

You can easily tailor this driver to any other infrared protocol by simply adapting

the defines from sirc_decode.h to the infrared protocol specification (Bit Duration,

Header Duration, Marge Tolerance, Number of bits...) and the command and

device tables.

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