AN4099 datasheet(18/39 Pages) STMICROELECTRONICS

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Infrared receiver

AN4099

18/39

Doc ID 023110 Rev 2

Infrared receiver

3.1

Hardware considerations

To improve noise rejection, the IR pulses are modulated at around 36 kHz, 38 kHz or

40 kHz. The easiest way to receive these pulses is to use an integrated IR

receiver/demodulator module like the TSOP1736 (5 V supply version) or TSOP34836 (3.3 V

supply version) or other equivalent part number (refer to Figure 15).

These are 3-pin devices that receive the infrared burst and output the demodulated bit

stream on the output pin which is connected directly to one of the STM32 microcontroller’s

GPIO pins or GP-Timers Input Capture channels. If TSOP1736 is used, the selected GPIO

must be Five volt Tolerant (FT). The output of the IR module is inverted compared to the

transmitted data (the data is idle high and logic "0" becomes logic "1" and vice versa).

Note:

The IR module needs two external components: a capacitor and a resistor (refer to the

related IR module datasheet for their values).

Figure 15.

Hardware configuration

3.2

Universal solution: software implementation using a

GP-Timer configured in PWM input mode

Each infrared protocol can be decoded using one of the timer peripherals embedded in the

STM32 microcontroller. This timer can be configured in PWM input mode and used to

sample the infrared frame bits. The timer input capture function is active on edges with

opposite polarity.

AI15771b

STM32

GPIOx

Out

Modulated signal

Demodulated and inver ted

signal

Infra-red

Remote control

IR r eceiver

module

3.3 V

3.3 V or 5 V

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