【正文】 decimal point es on. Using the jumpers switch through the memorized pulse durations that the PIC16C57 will have stored in its memory. If all of the reading except the first are below 40h, the infrared format is a modulating one. If half or more of the values show up as 0FFh, then the remote is nonmodulating.If the remote control is modulated, switch to a demodulating IR receiver. With the option selector still at 1, press a button on the remote control again until the decimal point es on. The series of memorized pulse durations will now probably include a lot of FFh values. If so, move the Option selector up until the values are in the 7h to 1Fh range. The Option selector has the optimum value for the option divisor to be used in the TMR0 register. To optimize range and reliability, several demodulating receivers may be tried. These are available from Sharp or Lite On. The modulating frequencies that are presently used are kHz, kHz, kHz, , 38 kHz, 39 kHz, 40 kHz, kHz, 48 kHz, and kHz[2]. The most mon are round 40 kHz. The best match for your remote control will give the longest range and most consistent results.Step 4:Decoding ones and zerosThe next step is to map out the characteristic pulse and gap lengths that represent ones and zeros. By pressing the same button on the remote, write down the series of numbers read by the PIC16C57 running the MEASURE .ASM program. Each odd numbered entry is the duration of a burst of IR from the remote control. Each even numbered entry is the duration of a gap between bursts of infrared. The lengths of these gaps and bursts define ones and zeros. Their order will depend on which button is pressed. Once the characteristic lengths have been discovered for a one and a zero, an algorithm can then be created with a counter to translate the lengths into ones and zeros.Step 5:Finding the Command LengthPress the same button again. The mand duration can also be found. This is necessary to determine if a button is being held down or a new mand of the same type is being issued. Most remote controls repeat the mand as long as the button is held down, the repetitions separated by a long dark time, usually 0FFh on an even numbered no long even numbered counts can be found, consider that some mands can be longer than 64 transitions. The option to delay counting is available for this reason. Insert jumper 1 and MEASURE. ASM will only start storing transition times after the 32nd transition.Step 6: Translating lengths to bitsOnce the characteristic lengths of ones and zeros have been found and the length of the typical mand has been found, a program can then be written to decode these lengths to ones and zeros and display them on the two digit display. Also a HOLD flag can be created which will be true as long as the button is being held down. Usually 1/8 second between mands indicates a new mand. Use this value to time out HOLD times and times between mands. is an example of a program that translates the gap lengths of the NEC6121 format to the four bytes that make up the information in each mand.Step 7:Create a button to code cross reference table implements a lookup table to translate the codes received to the actual button pressed. A counter is loaded with the highest number button that can be pressed, and the code is then looked up and pared with the code that was received. If no match, the counter is decremented until a match is found. When found, the counter then has the button number that was pressed. Note too, that more checking may be done at this level on some formats, such as having an address, a plement of the code following the code itself for checking. The result from all of the steps in decoding is that if a button is pressed on a remote control, that button number appears in a PIC16C57 file location. A mand such as channel up or channel down will appear as two set flags, one to indicate the mand, the other to indicate that it is active, HOLD. From this point the application can access these flags and files to respond appropriately.Note the following details of the code protection feature on PICmicro 174。, a short gap or burst is interpreted as a 39。