Le Anh Tu,

When you study the M3004LD data sheet you will notice that there is FLASH mode and MODULATED mode for the output that drives to the transmitter IR LED. Note that if the MODULATED mode is in use in your particular remote control the the modulation frequency is 1/12 of the oscillator frequency. Most common oscillator is 455KHz leading to an output modulation frequency of 455/12==37.9166 KHz.

You will then want to make sure that the IR receiver in the target equipment is set for a center frequency of 38 KHz. The part number for a typical receiver is TSOP1738 or TSOP1838.

Please also note that if modulation is in use and the IR receiver is of a type similar to those that I linked above (and Sharp makes similar modules in small tin boxes) then the IR receiver will filter out the modulation carrier wave of the IR signal and present the resulting envelope signal at its output. This signal will appear similar in timing as the flash mode timing that the data sheet for the transmitter shows although there will be some timing distortion caused by the receiver and stray IR light in the room.

One more thing needs to be considered. I noticed in your postings from several days ago that you indicated that this new remote control with the M3004LD is going to replace a remote control that used the PT2210 chip (datasheet here). The PT2210 chip uses the RC-5 transmission prototcol. This protocol is a Philips standard and you will find that Philips recommends that a carrier frequency of 36KHz be used for transmission of RC-5. (Note that I have visited and worked directly with the remote control engineers at Philips Corporate Design Center in Eindhoven , the Netherlands and I have written code several times to support the decoding of RC-5 protocol). You should carefully check to see if your existing hardware is setup with a 36KHz center frequency receiver or a 38KHz center frequency receiver.

It is quite possible for a new 38 KHz remote control to be received by a 36KHz IR receiver BUT you will have reduced overall perfornance. The receiver output pulse timing will be more distorted, the receiver will detect valid transmissions from shorter distances, and the receiver will be more sensitive to IR noise and multi path interference causing upset of an active transmission. I point this out just as a word of caution. After you check you may find you have no problem in your system. On the other hand you may find it necessary to substitute an alternate IR receiver in your equipment in order to obtain optimim performance. Note that if you are currently using IR receivers from Sharp or Everlight, you may want to consider switching over to the Vishay TSOP series. The TSOP product (previously from TEMIC) is far superior in terms of performance. In the TSOP series there are parts that are optimized for PCM type protocols like the M3004LD uses and then there are others that are optimized for the BIPHASE type protocols (RC-5) that the PT2210 uses. The differences in the TSOP11, TSOP12, TSOP17, and TSOP18 series parts relates to the time constants used in the demodulator inside the detector. From my experience I found the TSOP1736 and TSOP1738 worked nicely in the applications I was working with.

When I devised algorithms to decode IR remote control transmissions I had a scheme where I would use an IR detector connected to a bit on a PC parallel port, I would then write software that decoded the IR transmissions on the PC in DOS mode using Borland BC3.1. Once I learned enough about the protocol and what kind of timing measurement tolerances were needed to optimize decoding performance I would then move the algorithm to the embedded processor. (If only I had been able to do the IR decoding on the target platform in an 8051 type processor.....but no.....I was using the TPU (time processor unit) on board a Motorola MC68332 processor. Talk about something hard to learn how to program).

If you are interested in looking at the source code for one of the PC based decoding algorithms that I experimented with you can download a ZIP file of the source code here. The corresponding TPU code can be viewed in this ZIP file which I included here because the IR transmission scheme decoded by these programs in described in the TPU source code file. Note that the remote control supported by these algorithms used a combination of the NEC standard protocol which is very similar to that used by your M3004LD except it is 32 bits sequence, and a high speed BIPHASE protocol similar to RC-5. The NEC protocol at 10 Hz repeat rate was used for the normal buttons and the high speed protocol at 40 Hz repeat rate was used for the touch point arrow(s) button on the remote control. The company that makes this remote control is Interlink Electronics as their model IRC-TC which you can see on their web pages (just click the "product locator" box on the left side of the page).

Hope this info is useful
Michael Karas