Describe any infrared protocols, either for data or remote controlling a TV.

There are two broad families: consumer-IR remote-control protocols and IrDA data protocols.

Consumer IR remote control (TVs, AV gear) These send short command frames by modulating an IR LED onto a carrier, typically around 36–40 kHz (commonly ~38 kHz). The receiver (a demodulating IR module) is tuned to that carrier so ambient/DC light is rejected; what the MCU sees is the demodulated envelope of carrier bursts and gaps. Bits are encoded in the timing of those bursts/gaps. Common protocols:

• NEC: a leading AGC burst, then 8-bit address + its logical inverse and 8-bit command + its inverse, using pulse-distance encoding (a fixed burst followed by a short gap for "0" or a long gap for "1"). Includes a repeat code for held buttons.
• RC-5 / RC-6 (Philips): RC-5 uses Manchester (bi-phase) encoding with a toggle bit that flips on each new keypress (so the receiver can distinguish a held key from repeated presses). RC-6 is a faster, more capable successor.
• SIRC (Sony): pulse-width encoding (bit value determined by the length of the "on" burst), in 12-, 15-, or 20-bit variants.

The key design ideas across all of them: a modulated carrier for noise immunity, a known header/AGC pulse, and timing-based (pulse-distance, pulse-width, or Manchester) bit encoding, often with address+command and an inverse/checksum for integrity.

IrDA (data) For actual data transfer (not remote control), IrDA defines a stack for point-to-point links. The physical layer SIR reuses UART framing over IR at rates up to 115.2 kbps, with faster MIR/FIR modes up to 4 Mbps. It was common on older laptops, PDAs, and phones for file exchange before Bluetooth/Wi-Fi took over.

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