CN208953988U - A kind of tablet computer with RS232 interface - Google Patents

Abstract

The utility model relates to a kind of tablet computers with RS232 interface, including tablet computer shell and the PCB main board for being installed in tablet computer, PCB main board is equipped with the control module for exporting ttl signal, control module is equipped with ttl signal output end, ttl signal output end output level is 1.8V, PCB main board is additionally provided with RS232 interface, first level shifting circuit and second electrical level conversion circuit, the input terminal of first level shifting circuit be electrically connected with ttl signal output end with by TTL low transition be TTL high level, the input terminal of second electrical level conversion circuit is electrically connected so that TTL high level is converted to RS232 level with the output end of the first level shifting circuit, the output end of second electrical level conversion circuit is electrically connected with RS232 interface, the utility model can lead to The external computer equipment of RS2332 interface is crossed, realizes the data communication of tablet computer and computer equipment, it is user-friendly.

Description

A kind of tablet computer with RS232 interface

Technical field

The utility model relates to technical field of electronic products, more particularly to a kind of tablet computer with RS232 interface.

Background technique

As modern science and technology is maked rapid progress, tablet computer can plug-in external equipment (computer main equipment or other from setting It is standby) Lai Jinhang Function Extension and data communication, improve the function and performance of product, tablet computer is usually using 1.8VTTL level With peripheral device communication.Tablet computer product on the market is substantially without RS232 interface at present, but passes through in tablet computer needs The external computer equipment of RS232 interface carries out function when carrying out function and behavior extension, not then to be available this kind of RS232 interface Extension and data communication, use are very inconvenient.

Utility model content

To solve the above problems, the utility model provides a kind of tablet computer with RS232 interface, with RS232 Interface, it is user-friendly.

To solve above-mentioned purpose, the following technical solution that the utility model uses.

A kind of tablet computer with RS232 interface, including tablet computer shell and the PCB master for being installed in tablet computer Plate, PCB main board are equipped with the control module for exporting ttl signal, and control module is equipped with ttl signal output end, ttl signal output End output level is 1.8V, which is characterized in that PCB main board is additionally provided with RS232 interface, the first level shifting circuit and second electrical level Conversion circuit, the input terminal of the first level shifting circuit be electrically connected with ttl signal output end with by TTL low transition for TTL High level, the input terminal of second electrical level conversion circuit are electrically connected with by TTL high level with the output end of the first level shifting circuit RS232 level is converted to, the output end of second electrical level conversion circuit is electrically connected with RS232 interface.

As the further scheme of the utility model, the first level shifting circuit is equipped with for being by TTL low transition First electrical level transferring chip of TTL high level, the first electrical level transferring chip are set as SGM4553 chip, to be used for 1.8VTTL Low transition is 3.3VTTL high level.

As the further scheme of the utility model, second electrical level conversion circuit is equipped with for being converted to TTL high level The second electrical level conversion chip of RS232 level, second electrical level conversion chip are set as MAX232 chip, by 3.3VTTL high electricity Flat turn turns to RS232 level.

The beneficial effects of the utility model are as follows:

After TTL low transition is first TTL high level using the first level shifting circuit by the utility model, the is recycled TTL high level is converted into RS2332 level by two level shifting circuits, and is sent to RS2332 interface, by RS2332 interface outside Computer equipment is connect, realizes the data communication of tablet computer and computer equipment, it is user-friendly.

Detailed description of the invention

Fig. 1 is the schematic block circuit diagram of the utility model；

Fig. 2 is the circuit diagram of the utility model.

Specific embodiment

The utility model is further described below in conjunction with attached drawing.

Referring to figs. 1 to Fig. 2, a kind of tablet computer with RS232 interface, including tablet computer shell and it is installed in plate The PCB main board of computer, PCB main board are equipped with the control module 1 for exporting ttl signal, and control module 1 is exported equipped with ttl signal End, ttl signal output end output level are 1.8V, and PCB main board is additionally provided with RS232 interface 4, the first level shifting circuit 2 and the Two level shifting circuits 3, the input terminal of the first level shifting circuit 2 are electrically connected to turn TTL low level with ttl signal output end It is changed to TTL high level, the input terminal of second electrical level conversion circuit 3 is electrically connected to incite somebody to action with the output end of the first level shifting circuit 2 TTL high level is converted to RS232 level, and the output end of second electrical level conversion circuit 3 is electrically connected with RS232 interface 4, this is practical new TTL low transition is first recycling second electrical level conversion circuit 3 after TTL high level using the first level shifting circuit 2 by type TTL high level is converted into RS2332 level, and is sent to RS2332 interface, by the external computer equipment of RS2332 interface, Realize the data communication of tablet computer and computer equipment, it is user-friendly.

Referring to Fig. 2, first level shifting circuit 2 of the present embodiment is equipped with for being TTL high level by TTL low transition The first electrical level transferring chip, the first electrical level transferring chip is set as SGM4553 chip, for turning 1.8VTTL low level It is changed to 3.3VTTL high level, wherein the 7th pin of SGM4553 chip and the 8th pin are respectively connected to TTL signal output end 4th pin at the end TXIN and the end TTL signal output end RXIN, SGM4553 chip passes through parallel connection first resistor R1 and second resistance R2 is connect with the first pin of SGM4553 chip and the 8th pin respectively, and the first pin of SGM4553 chip passes through parallel connection first 8th pin of capacitor C1 ground connection, SGM4553 chip is grounded by the second capacitor C2 of parallel connection, and Fig. 2 shows the second electricity of the present embodiment Flat conversion circuit 3 is equipped with the second electrical level conversion chip for TTL high level to be converted to RS232 level, second electrical level conversion Chip is set as MAX232 chip, converts RS232 level for 3.3VTTL high level, the second pin of SGM4553 chip is logical It crosses series connection 3rd resistor R3 connect with the 11st pin of MAX232 chip, the third pin of SGM4553 chip, which passes through, connects the Four resistance R4 are connect with the 12nd pin of MAX232 chip, the second pin of MAX232 chip by series connection third capacitor C3 and 4th capacitor C4C4 ground connection, and the second pin of MAX232 chip can 5th capacitor C5 of parallel connection be grounded, the tenth of MAX232 chip the Three pins and the 14th pin are exported to the end TXD_OUT of RS232 interface 4 and the end RXD_OUT, and the present embodiment utilizes SGM4553 Chip first does 1.8VTTL low level to 3.3VTTL high level and converts, and then recycles MAX232 chip 3.3VTTL high level Conversion is to RS232 level, and circuit design is reasonable, and transmission performance is more stable.

Above-described embodiments merely represent several embodiments of the utility model, the description thereof is more specific and detailed, But it should not be understood as limiting the scope of the patent of the utility model.It should be pointed out that for the common of this field For technical staff, without departing from the concept of the premise utility, various modifications and improvements can be made, these all belong to In the protection scope of the utility model.Therefore, the scope of protection shall be subject to the appended claims for the utility model patent.

Claims (3)

1. a kind of tablet computer with RS232 interface, including tablet computer shell and the PCB main board for being installed in tablet computer, PCB main board is equipped with the control module for exporting ttl signal, and control module is equipped with ttl signal output end, ttl signal output end Output level is 1.8V, which is characterized in that PCB main board is additionally provided with RS232 interface, the first level shifting circuit and second electrical level and turns Change circuit, the input terminal of the first level shifting circuit be electrically connected with ttl signal output end with by TTL low transition for TTL high Level, the input terminal of second electrical level conversion circuit are electrically connected to turn TTL high level with the output end of the first level shifting circuit It is changed to RS232 level, the output end of second electrical level conversion circuit is electrically connected with RS232 interface.

2. a kind of tablet computer with RS232 interface according to claim 1, which is characterized in that the first level conversion Circuit is equipped with the first electrical level transferring chip for by TTL low transition being TTL high level, the setting of the first electrical level transferring chip For SGM4553 chip, with for by 1.8VTTL low transition for 3.3VTTL high level.

3. a kind of tablet computer with RS232 interface according to claim 2, which is characterized in that second electrical level conversion Circuit is equipped with the second electrical level conversion chip for TTL high level to be converted to RS232 level, the setting of second electrical level conversion chip For MAX232 chip, RS232 level is converted by 3.3VTTL high level.