Remote Control & Receiver

This 60-key remote (RC-319S) is for the entire 2nd generation INTEC275 components (amp, 2 tape decks, tuner, MD player, and CD player). The INTEC275 CD player receives commands from this remote with a Sharp GP1U571X IR detecting unit (one on the PCB).

This detector is no longer produced (recall that the CD player is manufactured in the late '90). For the PC mod, I will use compatible detector from Sharp (GP1UM271RK0F, shown on the left above). This unit has the same band-pass filter center frequency (38 kHz) as GP1U51X and also has the exact same height profile as GP1U571X. The latter guarantees the GP1UM271RK0F to fit properly with the front panel plastic molding.

Experimenting with GP1U571X and the Onkyo remote

To test the IR detector, I hooked it up straight to 5V source and scope probe:

Here's the signal received when POWER button is pressed:

The detector outputs low (0 V) or high (4.5 V) levels. The output signal is normally high, and the beginning of received message begins with an extended period of low level (~9.11 ms), followed by a shorter period of high (~4.45 ms). The ensuing pulsing pattern defines the remote control command. But how is the information coded?

Upon closer inspection, we see that the low period duration is consistent all the time (~0.61 ms) while the high period duration is bi-modal (either 0.52 ms or 1.63 ms long). Hence, most likely it is pulse-length coded. There are 32 high periods during pulsating period; therefore, each button is coded with 32 bits (4 bytes).

For our convention, we let the short period to represent 0 Bit and the long period to represent 1 Bit. Also, the bits are transmitted in MSB first fashion. Accordingly, the 32-bit codes (in hex) associated with all 60 keys are listed below.

Row	Col	Code	Button Name
1	1	0x4bb520df	POWER
1	2	0x4bb59b64	SPEAKER A
1	3	0x4bb55ba4	SPEAKER B
1	4	0x4b36f807	INPUT SELECTOR PREV
1	5	0x4b367887	INPUT SELECTOR NEXT
2	1	0x4bb510ef	SLEEP
2	2	0x4b3612ed	TIMER
2	3	0x4b36c23d	TIMER SETTING PREV
2	4	0x4b3642bd	TIMER SETTING NEXT
2	5	0x4b36629d	TIMER ENTER
3	1	0x4bb548b7	DECK-A REWIND
3	2	0x4bb58877	DECK-A FAST FORWARD
3	3	0x4bb5708f	DECK-A REVERSE PLAY
3	4	0x4bb530cf	DECK-A STOP
3	5	0x4bb5b04f	DECK-A FORWARD PLAY
4	1	0x4bb558a7	DECK-B REWIND
4	2	0x4bb59867	DECK-B FAST FORWARD
4	3	0x4bb56897	DECK-B REVERSE PLAY
4	4	0x4bb5c837	DECK-B STOP
4	5	0x4bb5a857	DECK-B FORWARD PLAY
5	1	0x4bb518e7	DECK-B RECORD/PAUSE
5	2	0x4bb5906f	TUNER FM
5	3	0x4bb550af	TUNER AM
5	4	0x4bb5807f	TUNER PRESET PREV
5	5	0x4bb500ff	TUNER PRESET NEXT
6	1	0x4b7422dd	MD REPEAT
6	2	0x4b7458a7	MD RECORD
6	3	0x4b7438c7	MD STOP
6	4	0x4b74f807	MD PAUSE
6	5	0x4b74d827	MD PLAY
7	1	0x4b74609f	MD DISPLAY
7	2	0x4b74e01f	MD SCROLL
7	3	0x4b7450af	MD RANDOM
7	4	0x4b747887	MD PREV TRACK
7	5	0x4bb5d827	MD NEXT TRACK
8	1	0x4bb57986	CD DISC
8	2	0x4b361ae5	CD DISPLAY
8	3	0x4bb538c7	CD STOP
8	4	0x4bb5f807	CD PAUSE
8	5	0x4bb5b847	CD PLAY
9	1	0x4bb50af5	CD 1
9	2	0x4bb58a75	CD 2
9	3	0x4bb54ab5	CD 3
9	4	0x4bb57887	CD PREV TRACK
9	5	0x4bb5b847	CD NEXT TRACK
10	1	0x4bb5ca35	CD 4
10	2	0x4bb52ad5	CD 5
10	3	0x4bb5aa55	CD 6
10	4	0x4b36ea15	CD RANDOM
10	5	0x4bb5a05f	MUTING
11	1	0x4bb56a95	CD 7
11	2	0x4bb5ea15	CD 8
11	3	0x4bb51ae5	CD 9
11	4	0x4b366a95	CD REPEAT
11	5	0x4bb540bf	VOLUME UP
12	1	0x4bb55aa5	CD --/---
12	2	0x4bb59a65	CD 10/0
12	3	0x4bb5eb14	CD MEMORY
12	4	0x4bb51be4	CD CLEAR
12	5	0x4bb5c03f	VOLUME DOWN

Note that the 8 MSBs (i.e., the first 2 hex digits) are always 0x4b, which can be used to identify the remote quickly. Otherwise, the codes appear fairly random. It would be interesting to know how they are chosen.