Customized Universal Mobile Phone Data Cable
- PRODUCT DETAIL
A common problem encountered by data cable vendors is that customers report that the data cable cannot be used. If you are sure that the phone is sent correctly, then the customer will not use the data cable. First, check whether the software in the CD supports the customer's mobile phone model. If you don’t support it, you can go to the Internet to download a corresponding software, so the general problem is solved. The key point: the data line is universal, the software is not universal. There is no particularly good way, after all, there are too many cell phone models.
Method of making mobile phone data line
The original mobile phone data cables are expensive, which discourages many users. Through the analysis and research of the data lines and schematic diagrams of various models of Siemens, Samsung, Alcatel, Lenovo, etc., the author found that most models on the market have the same data line principles, but the interface shape and definition are different. The data lines of many models can be self-made, as long as you make appropriate changes according to the definition of the data line interface of the actual model. This article takes Siemens 6688, 6618, 3618 and other mobile phones as examples to introduce the production of mobile phone data lines in detail for your reference.
Let's first look at the definition of the computer RS232C port (serial port, as shown in the figure):
① Carrier detection (DCD)
② Receive data (RXD)
③ Send data (TXD)
④ The data terminal is ready (DTR)
⑤ Signal ground wire (SG)
⑥ Data ready (DSR)
⑦ Request to send (RTS)
⑧ Clear to send (CTS)
⑨ Ringing indication (RI)
The signal is EIA level (-3--15V, +3-+15V). The interface (picture) definition of Siemens 6688 and other mobile phones:
① Ground wire, used for the negative pole of the charger and the ground of the data wire
② Left channel of earphone
③ Charger positive
④ Empty, don’t short-circuit with other pins
⑤ Data OUT
⑥ Data IN
⑧ The functions of the feet are the same. Switches (one of them is shorted to ground first, and the other is connected to the switch on the headset)
⑨ Ground, often used for MIC ground
⑩ MIC positive
⑾ Earphone right channel
⑿ The earphone is grounded. The signal is CMOS/TTL (0-3. 3V) level. Because the electrical characteristics of the computer serial port and the mobile phone data port (TTL circuit) are different, signal conversion must be performed to enable the two to communicate with each other.
Working principle of mobile phone data line (see picture): In RS232C, -5V to -15V represents 1, and +5V to +15V represents 0; In the TTL circuit, greater than 3V represents 1, and less than 0.2V represents 0. The MAX232 integrated circuit (MAX232 pin definition is shown in Figure 4) realizes the conversion of RS232C and TTL circuits, in which pin ⑧ receives the TXD (transmit data) signal sent from the 3 pin of the serial port, and outputs the signal from pin ⑨ to the 6 pin IO of the mobile phone after conversion. —RXD (data receiving) on; ⑩ The pin receives the IO_TXD (data transmission) signal sent from the mobile phone. Output from pin ⑦ to the 2-pin RXD (receive data) and 1-pin DCD (receive line signal detection) of the serial port. The working power of MAX232 is provided by the serial port. The 12V voltage output from the 4, 6, 7 and 8 pins of the serial port is rectified by two 1N14148 diodes, and then the voltage of 5V is stabilized by the 78L05 zener tube and output to pin ⒃ of MAX232 for the integrated block to work. The 5V power supply is also sent to the 3-pin of the plug, which can charge the phone. If you don’t want to use the charging function, you can not solder the 3-pin or add a small switch on the front. The 4 capacitance parameters of MAX232 have an influence on the transmission speed of the data line, and the manufacturer's recommended value of luF is used here (0.1uF for MAX232A and MAX3232). The capacitors of 470uF and 47uF are power filter capacitors. If you want the circuit to have a data transmission instruction function, you can add the instruction circuit in Figure 5.
Cell phone data line component selection:
The core of this circuit is the MAX232 integrated block. There are two common packages, one is dual in-line type, which is slightly larger in size and easy to solder; The other is a patch type, which is smaller in size. In addition, if you cannot find MAX232, you can also use RS232 transceiver integrated blocks such as MAX232A, HIN232, MAX220, MAX3232, IL32, etc. The pin definitions are the same as MAX232, and the first two integrated blocks are faster. 78L05 has the same appearance as ordinary transistors, so please pay attention to the pin definitions when purchasing. If the fever is found to be serious, it can be replaced by 7805, or a 1V voltage regulator tube and a current limiting resistor can be used instead. The welding of capacitors should pay attention to distinguish the positive and negative poles. It is better to add a 0.1uF CBB capacitor to both ends of the filter capacitor. The 4 parameter capacitors are best to use high-quality capacitors such as tantalum capacitors, and the capacity of luF or 0.1uF can be selected according to the different integrated blocks. The more difficult thing to find is the mobile phone plug, but it can be obtained from a waste charger with the same type of interface, but please note that all metal pins must be complete. The cable uses a shielded 6-core cable. The above materials can be purchased at electronic component stores or computer network consumables stores, and you can buy all of them at about 10 yuan.