IR RC5 & RC6 Protocol Guide: Manchester Encoding & Decoding

Core Technical Specifications

center Freq 36 kHz infrared carrier

modulation Bi-phase (Manchester) encoding

data Encoding RC5: 14 bits (2 start + 1 toggle + 5 address + 6 command). RC6: 21+ bits with mode field

operating Range 5–10 m (line of sight)

antenna IR LED (940 nm) / TSOP1736 receiver

tx Power IR LED 20–100 mA peak

bandwidth 36 kHz ±1 kHz

channel Spacing N/A

Real-World Devices & Applications

Consumer Electronics

Philips TVs and AV equipment
European universal remotes
Marantz, Denon, and other EU-brand audio equipment
Sky/Virgin Media set-top boxes (RC6 variant)
Xbox Media Center remotes (RC6)

Reference Circuits & Schematics

RC5 IR Receiver — TSOP1736

The TSOP1736 is tuned to 36 kHz for optimal RC5 reception. Pin-compatible with VS1838B but optimised for 36 kHz carrier.

Pin	Description
`VOUT`	Demodulated output (active LOW during burst)
`GND`	Ground
`VCC`	2.5–5.5V supply

Circuit Walk-Through

RC5 Manchester encoding means each bit period has a transition in the middle: HIGH→LOW = logic 1, LOW→HIGH = logic 0. The 889 µs half-bit period (1.778 ms per bit) at 36 kHz carrier. The toggle bit flips each time a button is pressed (but stays the same while held), allowing the receiver to distinguish a new press from a held key.

Signal Structure & Waveform Analysis

RC5 Frame Structure

RC5 uses Manchester encoding with a fixed 14-bit frame transmitted MSB first.

Start Bits

2 bits (always 1,1)

Two logic-1 start bits, 1.778 ms each

Toggle Bit

1 bit

Flips on each new key press

Address

5 bits

Device address (0–31), e.g., TV=0, VCR=5

Command

6 bits

Button command (0–63)

Timing Notes: Bit period: 1.778 ms (889 µs per half-bit). Total frame: ~25 ms. Repeat rate: ~114 ms. RC6 extends this with a mode field (3 bits) and trailer bit for wider addressing. RC6 header uses a 2.666 ms leader pulse + 889 µs gap.

Analysis & Capture Tips

Manchester decoding: look for transitions at 889 µs intervals
Toggle bit changes = new press vs held key
RC5 extended (RC5X): start bit 2 becomes MSB of 7-bit command (0–127)
Use IRremote Arduino library with RC5 decode enabled

Bench Troubleshooting & Repair Guide

1. 36 kHz vs 38 kHz

Oscilloscope / Frequency counter

RC5 uses 36 kHz carrier. A 38 kHz receiver (VS1838B) will work but with reduced sensitivity/range. For best results, use TSOP1736.

2. Toggle Bit Issues

Logic Analyser / IRremote debug

If receiver doesn’t distinguish new press from repeat, check toggle bit handling in decoder firmware. The toggle bit must be tracked across frames.

3. Address Conflicts

Remote control documentation

RC5 only has 32 addresses. Multiple Philips devices in the same room may conflict. Use address reassignment (device menu) or IR routing.

IR RC5 / RC6