The RC-5 protocol was developed by Philips in the early 1980s as a semi-proprietary consumer IR (infrared) remote control communication protocol for consumer electronics. It was subsequently adopted by most European manufacturers, as well as by many US manufacturers of specialty audio and video equipment. The other main protocol relevant to consumer electronics is the NEC protocol, which is largely used by Japanese manufacturers.
The RC-5 protocol, when properly implemented, has the advantage that any CD handset (for example) may be used to control any compatible brand of CD player. By comparison, the NEC protocol assigns each brand its own unique header(s) after which may follow any desired command set; this confers the advantage that there cannot be any interference between remote handsets for pieces of equipment made by different manufacturers.
Protocol details
The basics of the protocol are well known. The handset contains a keypad and a transmitter integrated circuit (IC) driving an IR LED. The command data is a Manchester-coded bitstream modulating a 36 kHz carrier. (Often the carrier used is 38 kHz or 40 kHz, apparently due to misinformation about the actual protocol.) The IR signal from the transmitter is detected by a specialized IC with an integral photo-diode, and is amplified, filtered, and demodulated so that the receiving device can act upon the received command. RC-5 only provides a one-way link, with information travelling from the handset to the receiving unit.
The command comprises 14 bits:
A start bit which is always logic 1 and allows the receiving IC to set the proper gain. A field bit which denotes whether the command sent is in the lower field (logic 1 → 0 to 63 decimal) or the upper field (logic 0 → 64 to 127 decimal). Originally a second start bit, the field bit was added later by Philips when it was realized that 64 commands per device were insufficient. Many devices still use the original system. A control bit which toggles with each button press. This allows the receiving device to distinguish between two successive button presses (such as "1", "1" for "11") as opposed to the user simply holding down the button and the repeating commands being interrupted by a person walking by, for example. A five-bit system address that selects one of 32 possible systems. A six-bit command that (in conjunction with the field bit) represents one of the 128 possible RC-5 commands.
The 36 kHz carrier frequency was chosen to render the system immune to interference from TV scan lines. Since the repetition of the 36 kHz carrier is 27.778 μs and the duty factor is 25 %, the carrier pulse duration is 6.944 μs. Each bit of the RC-5 code word contains 32 carrier pulses, and an equal duration of silence, so the bit time is 64×27.778 μs = 1.778 ms, and the 14 symbols (bits) of a complete RC-5 code word take 24.889 ms to transmit. The code word is repeated every 113.778 ms (4096 ÷ 36 kHz) as long as a key remains pressed. (Again, please note that these timings are not strictly followed by all manufacturers, due to a lack of widespread distribution of accurate information on the RC-5 protocol.)
System and command codes
While the RC-5 protocol is well known and understood, what is not so well documented are the system number allocations and the actual RC-5 commands used for each system. The information provided below is the most complete and accurate information available at this time. It is from a printed document from Philips dated December 1992 that is unfortunately not available in electronic format (e.g., PDF), nor is an updated version available. This information is provided so that companies that wish to use the RC-5 protocol can use it properly, and avoid conflicts with other equipment that may or may not be using the correct system numbers and commands.
Accuracy of information
The information in the tables on this page is known to be accurate. Yet it is also clear that there are many gaps in these tables. For example, there is no category listing for DVD players in the system table. (They were not developed until five years after the date of publication of the material from which this information was obtained.) It would obviously be useful therefore to expand these tables with known accurate information. At this time, there are only a few possible ways to do so.
The first would be to capture the IR bitstream from the handset of newer Philips products, such as DVD players and analyze them to see what system number is used. The other would be to use the popular Philips Pronto series of programmable remote controls. These can be programmed to operate Philips components using the RC-5 protocol. Again, the bitstream output of the handset would need to be captured and analyzed. The only other way is to obtain the appropriate documents directly from Philips.
System number allocations
+ Table 1: System number allocations for RC-5 System number Description Command tables 0 TV 1 (TV receiver 1) 2, 3, 4a 1 TV 2 (functions and command numbers as system 0) 2, 3, 4a 2 Txt (teletext) 2, 3, 5 3 Extension to TV 1 and TV 2 2, 4b 4 LV (LaserVision player) 2, 3, 6 5 VCR 1 (video cassette recorder 1) 2, 3, 7a 6 VCR 2 (functions and commands as system 5) 2, 3, 7a 7 Reserved 8 Sat 1 (satellite TV receiver 1) 2, 3, 8 9 Extension to VCR 1 and VCR 2 2, 7b 10 Sat 2 (functions and commands as system 8) 2, 3, 8 11 Reserved 12 CD-Video (compact disc video player) 2, 3, 9 13 Reserved 14 CD-Photo (photo on compact disc player) 2, 3, 10 15 Reserved 16 Preamp 1 (audio preamplifier 1) 2, 11 17 Tuner (radio tuner) 2, 12 18 Rec 1 (analog cassette recorder) 2, 13 19 Preamp 2 (functions and commands as system 16) 2, 11 20 CD (compact disc player) 2, 14 21 Combi (audio stack or record player) 2, 15 22 Sat (audio satellite) 2, 16 23 Rec 2 (functions and commands as system 18) 2, 11 24 Reserved 25 Reserved 26 CD-R (compact disc recorder) 2, 17 27 Reserved 28 Reserved 29 Lighting 30 Reserved 31 Reserved
System number recommendations
As can be seen, this information is out of date. There are no longer any systems using CD-Video or CD-Photo, for example. In addition, many of the "Reserved" system numbers have no doubt been allocated by Philips during the intervening 16 years. In order to maintain compatibility, it would be helpful to obtain this information. Unfortunately, this has proven to be difficult.
When designing a product using the RC-5 protocol, the designer must follow the published information as closely as possible. For example, one surround-sound processor from a US specialty manufacturer used the system number 16, designated for "Preamp 1". This caused many problems with home theater installations that also included a separate two-channel preamplifier, which if of US or European origin, would also use the RC-5 protocol with system number 16. If the designers of the surround-sound processor had the correct information available to them, it would have been obvious that a better choice would have been to use system number 19, designated for "Preamp 2", as this would have avoided needless conflict between products.
Command tables
Over time, the information will also be added for the command tables so that all of the available information regarding the RC-5 protocol is gathered in one place. The information in the command tables shown in standard font was obtained from the Philips publication referenced at the bottom of this page. Information in italics is information that is known to be accurate, as it was derived by one of the methods described above.
+ Table 2: RC-5 commands common to all systems Command Function Command Function 0 to 9 Digit entries 0 to 9 78 Decrease linear control setting 16 Increase sound volume 80 Move cursor or actuator upwards 17 Decrease sound volume 81 Move cursor or actuator downwards 18 Increase screen/display brightness 82 Switch screen/display menu on 19 Decrease screen/display brightness 83 Switch screen/display menu off 22 Increase bass response 84 Display A/V system status 23 Decrease bass response 85 Move cursor or actuator to the left 24 Increase treble response 86 Move cursor or actuator to the right 25 Decrease treble response 87 Acknowledge; execute function selected by cursor 26 Shift sound balance to the right 118 Select functions defined as sub-mode 27 Shift sound balance to the left 119 Select functions defined as options sub-mode; e.g., calendar, alarm, time 63 Select system mode of RC transmitter 123 Connect two items via Euroconnector 71 Dim local display 124 Disconnect two items connected via Euroconnector 77 Increase linear control setting
+ Table 3: RC-5 commands common to all video systems except TV and VCR extension systems 3 and 9 Command Function Command Function 20 Increase color saturation 95 Select PIP source 21 Decrease color saturation 96 Mosaic/multi-PIP 88 PIP on/off 97 Digital noise reduction of picture 89 PIP shift 98 Store main picture 90 PIP/main picture swap 99 PIP strobe; displays a photo-finish 91 Strobe main picture on/off 100 Recall main stored picture 92 Multi-strobe 101 PIP freeze 93 Main picture frame frozen 102 Step up PIP options and display source 94 3/9 multi-scan: (search for 9 TV pictures and display in 9 PIPs) 103 Step down PIP options and display source Commands for video extension systems 3 (TV) and 9 (VCR) which use the common video command numbers are given in Tables 4b (TV) and 7b (VCR).
+ Table 4a: Additional RC-5 commands for TV 1 and TV 2 (systems 0 and 1) Command Function Command Function 10 1/2/3 digit entry 59 View data; advance (USA only) 11 Channel/program/freq; 11 (Japan) 60 TXT/TV toggle; 12 (Japan only) 12 Standby 61 System standby 13 Master mute/de-mute 62 Picture crispener (contour boost) 14 Personal preference settings 64 15 Display user info on screen 65 28 Increase picture contrast 66 29 Decrease picture contrast 67 30 Search up 68 31 Decrease tint/hue 69 32 Channel/program up 70 Audio response for speech/music 33 Channel/program down 72 34 Last viewed program/channel 73 35 Select stereo sound channel/language 74 36 Spatial stereo 75 37 Stereo/mono 76 38 Sleep timer 79 Select sound functions in sequence 39 Increase tint/hue 104 Alter PIP size step-by-step 40 Switch RF inputs 105 Select vision functions in sequence 41 Store; Vote (France only) 106 Actuate colored or other special keys 42 Display time 107 Actuate function highlighted red 43 Scan forward; increment (USA only) 108 Actuate function highlighted green 44 Decrement (USA only) 109 Actuate function highlighted yellow 45 110 Actuate function highlighted cyan 46 Secondary control/menu (USA only) 111 Index page/white function 47 Show clock 112 Next option 48 Pause 113 Previous option 49 Erase/correct entry 114 50 Rewind 115 51 Go to 116 52 Wind 117 53 Play 120 54 Stop 121 55 Record 122 Store open/close 56 External 1 125 57 External 2 126 58 127 Parental access via PIN code
+ Table 4b: RC-5 commands for TV1 and TV2 extension (system 3) other than those listed in Table 2 Command Function Command Function 10 4 default video settings (Far East) 67 Program 10 (Far East) 11 4 default audio settings (Far East) 68 Program 11 (Far East) 12 69 Program 12 (Far East) 13 70 14 72 4 default video settings (Far East) 15 73 4 default audio settings (Far East) 20 74 21 75 28 Pay TV channel + 76 29 Pay TV channel − 79 30 Radio channel + 88 Pay TV channel + 31 Radio channel − 89 Pay TV channel − 32 Tilt cabinet forward 10 degrees max 90 Radio channel + 33 Tilt cabinet backward 10 degrees max 91 Radio channel − 34 92 35 93 36 94 37 95 38 96 39 97 40 98 41 99 42 100 43 101 44 102 45 103 46 104 Tilt cabinet forward 10 degrees max 47 105 Tilt cabinet backward 10 degrees max 48 106 49 107 50 108 51 109 52 110 53 111 54 112 55 113 56 External 3 114 57 External 4 115 58 116 59 117 60 120 External 3 61 121 External 4 62 Change 4:3 picture format to 16:9 122 Channel setting menu 64 125 65 126 Change 4:3 picture format to 16:9 66 127