The module must be modulated with signal to work normally, common fixed code coding devices such as PT2262/2272, as long as they are directly connected, it is very simple, because it is a special coding chip, so the effect is very good, and the transmission distance is very long.
Another important use of the module is to cooperate with the single-chip microcomputer to achieve data communication, at this time there are certain skills:
1. Reasonable communication rate
The maximum transmission data rate of the data module is 9.6KBs, which is generally controlled at about 2.5k, and too high the data rate will reduce the receiving sensitivity and increase the bit error rate or even fail to work at all.
2. Reasonable information code format
When the microcontroller and module work, they usually define their own transmission protocol, no matter what modulation mode is used, the information code format to be transmitted is very important, which will directly affect the reliable transmission and reception of data.
The code group format is recommended
Preamble + Sync Code + Data Frame, the length of the preamble should be greater than 10ms to avoid background noise, because the first bit of the data received by the receiving module is very easy to be interfered with (i.e., zero level interference) and cause the received data error. Therefore, CPU decoding can be used to add some garbled codes before the data identification bit to suppress zero-level interference. The synchronization code is mainly used to distinguish it from the preamble code and data. There are certain characteristics that allow the software to identify the sync code through a certain algorithm and prepare for the received data.
The data frame should not be non-zero-return code, let alone long 0 and long 1. Use Manchester code or POCSAG code, etc.
3. The interference of single-chip microcomputer to the receiving module
It is generally normal when the single-chip microcomputer simulates 2262, but the single-chip microcomputer simulates 2272 when decoding, it is usually found that the remote control distance is shortened a lot, this is because the frequency multiplier of the clock frequency of the single-chip microcomputer will interfere with the receiving module, the electromagnetic interference of the single-chip microcomputer of the 51 series is relatively large, the 2051 is slightly smaller, and the PIC series is relatively small, and we need to adopt some anti-interference measures to reduce interference.
For example, the single-chip microcomputer and the remote control receiving circuit are powered by two 5-volt power supplies respectively, and the receiving board is powered by a 78L05 alone, and the clock area of the single-chip microcomputer is far away from the receiving module, reducing the working frequency of the single-chip microcomputer, and adding shielding in the middle.
It is best to make an isolation circuit when the receiving module interfaces with the 51 series single-chip microcomputer, which can better curb the electromagnetic interference of the single-chip microcomputer to the receiving module.
When the receiving module is working, the output is generally a high level pulse, not a DC level, so it can not be tested with a multimeter, and a light-emitting diode can be connected in series with a 3K resistor to monitor the output status of the module during debugging.
When the wireless data module and PT2262/PT2272 and other special codec chips are used, the connection is very simple, as long as it is directly connected, the transmission distance is ideal, generally more than 600 meters, if it is used with a single-chip microcomputer or microcomputer, it will be interfered by the clock of the single-chip microcomputer or microcomputer, resulting in a significant decrease in the transmission distance, and the general practical distance is within 200 meters.