Signal Analyzer for Infrared Remote Control

Transcription

1 More products at Document: Datasheet Date: 26-Jul-13 Model #: 1145 Product s Page: Signal Analyzer for Infrared Remote Control The board receives IR signals from existing remote controls and displays the waveform on PC through USB interface. It is powered from USB itself and uses inbuilt windows driver. PC software can show complete capture signal or you can zoom to particular signal area of interest. The captured information can be used to view, recognize or reproduce the signal. Anyone ever tried to decode an IR remote would know how difficult it is to create programming to decode the signal without accurately measuring signal length. During our development work, we came across many remote controls of different kinds and all kind of formats from our customers, so we developed a solution which can easily capture the remote control signals without the need to open it or destroy it. After we got the accurate data from remote controls, we used that information to identify the type of remotes and make decoder program. We also used this information to create encoders ICs for IR remote controls.

2 Features The board is designed with high-speed USB micro-controller and high accurate measuring in micro second resolution. Receive the signals directly from the remote controller, no need to destroy or open the remote controller when testing. The intact waveform can be showed clearly and steadily on PC; most of the oscilloscope doesn t show this way. It can test the width of pulse, the length of code, Number of bits, lead code, system code, key code, repeat code, etc Support 35 to 41KHz signals carriers remotes from all are between this frequency. Uses inbuilt windows USB drivers so no need to install or troubleshoot external drivers. Appears to windows as HID input device. The program run under Windows XP or Windows 7/8(32 & 64 bit OS), the interface is functional, friendly & easy to use. Supports any waveform Zoom in, Zoom out & bit number indicator. Get time between any two points. Receive correctly the commands from TV, VCR, VCD, DVD, AC remote controllers, or any. More Images 2 Sunrom Technologies Your Source for Embedded Systems Visit us at

3 PC Software Download software setup from the product page After running setup you will get icon on desktop or start software from start menu. You can connect the board to USB before starting software or after starting. Sequence does not matter as the software will keep searching for hardware until found. This makes the solution truly plug and play. This PDF file also opens when you click on View Help button. If you have not connected the hardware to USB you will get following message. Now it s time to get an infrared remote in front of board and press any key to start using. 3

4 Here is the screen for RC5 type remote control. We can now zoom into particular sample. To zoom in select mouse from left to right. Zoom out by selecting right to left. Here is the zoomed signal, you can zoom even further to each bit. On top you can see bit numbers, and below are timings. 4

5 NEC type remote signals looks like this, You can see the starting signal and then repeat pulses. Let s zoom into signal to view its more details. 5

6 Locating type of protocol of your remote Once you have information of what type of signal your remote is transmitting, it s time to identify the type of protocol it is following. Normally you will come across major three types of protocol in use in today s products unless you are using some custom remote or obsolete remote. 1. Philips RC5 Protocol 2. NEC Protocol (Also called JVC protocol, Most Widely used in AC remotes) 3. Sony SIRC Protocol Let us cover each protocol details in this document Philips RC5 Protocol The RC5 code from Philips is possibly the most used protocol by hobbyists, probably because of the wide availability of cheap remote controls. The protocol is well defined for different device types ensuring compatibility with your whole entertainment system. Features of Protocol 5 bit address and 6 bit command length Bi-phase coding (aka Manchester coding) Carrier frequency of 36kHz or 38kHz Constant bit time of 1.778ms (64 cycles of 36 khz), Different timing for 38Khz, Should be adjusted in decoder part by monitoring first two bits. Manufacturer Philips Modulation RC5 Modulation The protocol uses bi-phase modulation (or so-called Manchester coding) of a 36kHz IR carrier frequency. All bits are of equal length of 1.778ms in this protocol, with half of the bit time filled with a burst of the 36kHz carrier and the other half being idle. A logical zero is represented by a burst in the first half of the bit time. A logical one is represented by a burst in the second half of the bit time. The pulse/pause ratio of the 36kHz carrier frequency is 1/3 or 1/4 which reduces power consumption. Protocol The drawing below shows a typical pulse train of an RC-5 message. This example transmits command $35 to address $05. 6

7 RC-5 Pulse Train The first two pulses are the start pulses, and are both logical "1". Please note that half a bit time is elapsed before the receiver will notice the real start of the message. The 3rd bit is a toggle bit. This bit is inverted every time a key is released and pressed again. This way the receiver can distinguish between a key that remains down, or is pressed repeatedly. The next 5 bits represent the IR device address, which is sent with MSB first. The address is followed by a 6 bit command, again sent with MSB first. A message consists of a total of 14 bits, which adds up to a total duration of 25 ms. Sometimes a message may appear to be shorter because the first half of the start bit S1 remains idle. And if the last bit of the message is a logic "0" the last half bit of the message is idle too. As long as a key remains down the message will be repeated every 114ms. The toggle bit will retain the same logical level during all of these repeated messages. It is up to the receiver software to interpret this auto repeat feature. NEC Infrared Transmission Protocol The NEC IR transmission protocol uses pulse distance encoding of the message bits. Each pulse burst (mark RC transmitter ON) is 562.5μs in length, at a carrier frequency of 38kHz (26.3μs). Logical bits are transmitted as follows: Logical '0' a 562.5μs pulse burst followed by a 562.5μs space, with a total transmit time of 1.125ms Logical '1' a 562.5μs pulse burst followed by a ms space, with a total transmit time of 2.25ms When a key is pressed on the remote controller, the message transmitted consists of the following, in order: a 9ms leading pulse burst (16 times the pulse burst length used for a logical data bit) a 4.5ms space the 8-bit address for the receiving device the 8-bit logical inverse of the address the 8-bit command the 8-bit logical inverse of the command a final 562.5μs pulse burst to signify the end of message transmission. The four bytes of data bits are each sent least significant bit first. Figure 1 illustrates the format of an NEC IR transmission frame, for an address of 00h( b) and a command of ADh ( b). Example message frame using the NEC IR transmission protocol. 7

8 Notice from Figure 1 that it takes: 27ms to transmit both the 16 bits for the address (address + inverse) and the 16 bits for the command (command + inverse). This comes from each of the 16 bit blocks ultimately containing eight '0's and eight '1's - giving (8 * 1.125ms) + (8 * 2.25ms). 67.5ms to fully transmit the message frame (discounting the final 562.5μs pulse burst that signifies the end of message). Repeat Codes If the key on the remote controller is kept depressed, a repeat code will be issued, typically around 40ms after the pulse burst that signified the end of the message. A repeat code will continue to be sent out at 108ms intervals, until the key is finally released. The repeat code consists of the following, in order: a 9ms leading pulse burst a 2.25ms space a 562.5μs pulse burst to mark the end of the space (and hence end of the transmitted repeat code). Figure illustrates the transmission of two repeat codes after an initial message frame is sent. 8

9 Sony SIRC Protocol It appears that 3 versions of the protocol exist: 12-bit (described on this page), 15-bit and 20-bit versions. The 15-bit and 20-bit versions differ in the number of transmitted bits per command sequence. Features 12-bit, 15-bit and 20-bit versions of the protocol exist (12-bit described here) 5-bit address and 7-bit command length (12-bit protocol) Pulse width modulation Carrier frequency of 40kHz Bit time of 1.2ms or 0.6ms Modulation SIRC Modulation The SIRC protocol uses a pulse width encoding of the bits. The pulse representing a logical "1" is a 1.2ms long burst of the 40kHz carrier, while the burst width for a logical "0" is 0.6ms long. All bursts are separated by a 0.6ms long space interval. The recommended carrier duty-cycle is 1/4 or 1/3. Protocol The picture above shows a typical pulse train of the SIRC protocol. With this protocol the LSB is transmitted first. The start burst is always 2.4ms wide, followed by a standard space of 0.6ms. Apart from signaling the start of a SIRC message this start burst is also used to adjust the gain of the IR receiver. Then the 7-bit Command is transmitted, followed by the 5-bit Device address. In this case Address 1 and Command 19 is transmitted. Commands are repeated every 45ms(measured from start to start) for as long as the key on the remote control is held down. 9