21. Infrared interface (IRTIM)

An infrared interface (IRTIM) for remote control is available on the device. It can be used with an infrared LED to perform remote control functions.

It uses internal connections with USART1, USART2, TIM16, and TIM17 as shown in Figure 217 .

To generate the infrared remote control signals, the IR interface must be enabled and TIM16 channel 1 (TIM16_OC1) and TIM17 channel 1 (TIM17_OC1) must be properly configured to generate correct waveforms.

The infrared receiver can be implemented easily through a basic input capture mode.

Figure 217. IRTIM internal hardware connections with TIM16 and TIM17

Figure 217: IRTIM internal hardware connections with TIM16 and TIM17. The diagram shows a central IRTIM block with multiple inputs and one output. Inputs include TIM17_CH1 (high-frequency carrier signal), TIM16_CH1 (modulation envelope signal), USART1, and USART2. The TIM16_CH1 signal passes through a multiplexer controlled by IR_MOD[1:0] bits. The output of the multiplexer and the TIM17_CH1 signal are inputs to an AND gate. The output of the AND gate is then passed through an OR gate controlled by the IR_POL bit. The final output is IR_OUT, which shows a modulated infrared signal. The diagram is labeled MSv69040V1.
Figure 217: IRTIM internal hardware connections with TIM16 and TIM17. The diagram shows a central IRTIM block with multiple inputs and one output. Inputs include TIM17_CH1 (high-frequency carrier signal), TIM16_CH1 (modulation envelope signal), USART1, and USART2. The TIM16_CH1 signal passes through a multiplexer controlled by IR_MOD[1:0] bits. The output of the multiplexer and the TIM17_CH1 signal are inputs to an AND gate. The output of the AND gate is then passed through an OR gate controlled by the IR_POL bit. The final output is IR_OUT, which shows a modulated infrared signal. The diagram is labeled MSv69040V1.

All standard IR pulse modulation modes can be obtained by programming the two timer output compare channels.

TIM17 is used to generate the high frequency carrier signal, while TIM16 or alternatively USART1 or USART42 generates the modulation envelope according to the setting of the IR_MOD[1:0] bits in the SYSCFG_CFGR1 register.

The polarity of the output signal from IRTIM is controlled by the IR_POL bit in the SYSCFG_CFGR1 register and can be inverted by setting of this bit.

The infrared function is output on the IR_OUT pin. The activation of this function is done through the GPIOx_AFRx register by enabling the related alternate function bit.

The high sink LED driver capability (only available on the PB9 and PC14 pins) can be activated through the I2C_PB9_FMP bit and/or I2C_PC14_FMP bit in the SYSCFG_CFGR1 register and used to sink the high current needed to directly control an infrared LED.