Signal Analyzer for Infrared Remote Control Features - Sunrom ...

PC SoftwareDownload software setup from the product pagehttp://www.sunrom.com/178After 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 untilfound. 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.3Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com

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.5Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com

Locating type of protocol of your remoteOnce you have information of what type of signal your remote is transmitting, it’s time to identify thetype of protocol it is following. Normally you will come across major three types of protocol in use intoday’s products unless you are using some custom remote or obsolete remote.1. Philips RC5 Protocol2. NEC Protocol (Also called JVC protocol, Most Widely used in AC remotes)3. Sony SIRC ProtocolLet us cover each protocol details in this documentPhilips RC5 ProtocolThe RC5 code from Philips is possibly the most used protocol by hobbyists, probably because ofthe wide availability of cheap remote controls.The protocol is well defined for different device types ensuring compatibility with your wholeentertainment 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 beadjusted in decoder part by monitoring first two bits.• Manufacturer PhilipsModulationRC5 Modulation The protocol uses bi-phase modulation (or so-called Manchester coding) of a36kHz IR carrier frequency. All bits areof equal length of 1.778ms in thisprotocol, with half of the bit time filledwith a burst of the 36kHz carrier and theother half being idle. A logical zero isrepresented by a burst in the first half ofthe bit time. A logical one is represented by a burst in the second half of the bit time. Thepulse/pause ratio of the 36kHz carrier frequency is 1/3 or 1/4 which reduces power consumption.ProtocolThe drawing below shows a typical pulse train of an RC-5 message. This example transmitscommand $35 to address $05.6Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com

RC-5 Pulse TrainThe first two pulses are the start pulses, and are both logical "1". Please note that half a bit time iselapsed 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. Thisway 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 isfollowed 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 amessage may appear to be shorter because the first half of the start bit S1 remains idle. And if thelast 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 retainthe same logical level during all of these repeated messages. It is up to the receiver software tointerpret this auto repeat feature.NEC Infrared Transmission ProtocolThe NEC IR transmission protocol uses pulse distance encoding of the message bits. Each pulseburst (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 1.6875ms space, with a total transmit time of 2.25msWhen 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 IRtransmission frame, for an address of 00h(00000000b) and a command of ADh (10101101b).Example message frame using the NEC IR transmission protocol.7Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com

Notice from Figure 1 that it takes:• 27ms to transmit both the 16 bits for the address (address + inverse) and the 16 bits for thecommand (command + inverse). This comes from each of the 16 bit blocks ultimatelycontaining 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 thatsignifies the end of message).Repeat CodesIf the key on the remote controller is kept depressed, a repeat code will be issued, typically around40ms 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. Therepeat 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 repeatcode).Figure illustrates the transmission of two repeat codes after an initial message frame is sent.8Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com

Sony SIRC ProtocolIt appears that 3 versions of the protocol exist: 12-bit (described on this page), 15-bit and 20-bitversions. The 15-bit and 20-bit versions differ in the number of transmitted bits per commandsequence.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 0.6msModulationSIRC Modulation The SIRC protocol uses a pulse width encoding of the bits. The pulserepresenting a logical "1" is a 1.2ms long burst of the 40kHz carrier, while the burst width for alogical "0" is 0.6ms long. All bursts are separated by a 0.6ms long space interval. Therecommended carrier duty-cycle is 1/4 or 1/3.ProtocolThe picture above shows a typical pulse train of the SIRC protocol. With this protocol the LSB istransmitted first. The start burst is always 2.4ms wide, followed by a standard space of 0.6ms. Apartfrom signaling the start of a SIRC message this start burst is also used to adjust the gain of the IRreceiver. Then the 7-bit Command is transmitted, followed by the 5-bit Device address. In this caseAddress 1 and Command 19 is transmitted.Commands are repeated every 45ms(measured from start to start) for as long as the key on theremote control is held down.9Sunrom Technologies Your Source for Embedded Systems Visit us at www.sunrom.com