Serial expansion card development history

Device network has become a consensus and inevitable trend. In order to get higher efficiency and strive for competitive advantages, the establishment of a networked system has become a top priority. The Application of serial port card is the earliest in the computer, the external interface is the RS-232 interface, and then extended to the RS-232 and RS-422, RS-485 interface form.

Figure 1 Serial Port product Workflow

As a serial port product, the core working mechanism is as follows: after data is generated from the production end (usually PC or various specialized machine devices, transmits data to the 16C550 series UART (Universal asynchronous transceiver) through the parallel data bus, and then passes through the serial bus to a small chip. As a converter, the chip sends the data signal conversion format to an external interface and transmits it to the receiver. the entire workflow is shown in step 1.

The Application of ASIC technology greatly reduces the number of traditional IC, built-in automatic data Direction Control (ADDC) function, RS-485 half duplex in the RS-232 comport control is simpler, at the same time, RS-485 programming is also relatively simple, the development time is reduced.

For multi-serial port cards, the difference between the workflow and single-port serial port cards is not very big in terms of working mechanism. The focus is only on the number of UART cards. Multi-serial port cards can be divided into synchronous and asynchronous cards, for example, in the product provided by micro-embedded, there are two synchronous serial port cards and many asynchronous multi-serial port cards. Currently, most asynchronous communication multi-serial port cards are extended on the CPU card bus and become an intelligent interface card to save the time consumed by the host CPU to transport data and improve work efficiency, for example, an intelligent serial port card with two interfaces is shown in figure 2.

Figure 2 smart multi-serial-port card Workflow

The micro-embedded series multi-serial port cards are very suitable for the harsh environment of industrial sites. This series of products reduce the system wait time to as little as possible, improving the working time and stability. For micro-embedded series multi-serial card products, the most notable feature is the provision of RS-232 and RS-422/485 mutual interface conversion, and optional photoelectric isolation (Optical Isolation) and the surge protection function (Surge Protection) to improve the stability of system operation.

Figure 3 network serial port card Workflow

At present, a large number of network systems are established and are in demand for a longer distance. network serial ports are called out to integrate the corresponding OS into the firmware (including CPU, Ram, OS, and so on, it is equal to "placing" the required software in the interface card. In this way, the information is no longer as in the past, just transferred data at close distance, and the control of distant devices is achieved, it needs to be implemented through the network. Therefore, the Protocol applied to spread data on the network must be written into the data packet before transmission.

Figure 4 connected servers of Serial Devices

As shown in figure 3, data is converted into data packets by using the TCP/IP protocol, as a packet that contains the TCP/IP protocol and can be identified and transmitted by the network, it is transmitted from the control end to the device end through the network or from the device end to the control end, this completely breaks the restrictions on data transmission due to the data format of the serial port. Data is transmitted over the network to a host farther away, or even over the Internet, extend the transmission distance to an infinite number. For micro-embedded serial port equipment servers, it is more important to fully integrate the conversion work into the product. Through this work, the traditional interface and operation methods are maintained for the customer, so that the customer does not have to force themselves to adapt to the "network" problem. The network transmission capability is achieved through the same operation form as the ordinary serial port. What is included in the TCP/IP package is no longer simple raw data, but data automatically compiled by firmware. After the data arrives at the destination address, the installed driver automatically performs a reverse operation on the compilation to obtain the original data, ensuring effective transmission. At the same time, the user can avoid tedious compilation.