Anti Shaking RS485 2.0MP CCTV IP Camera Robot Mounted FCC

The RS485 standard allows the user to configure inexpensive local networks and multidrop communications links using twisted pair wire. To provide a convenient means of attaching two grounds to the serial cable, there are several pins (labeled DGND) on the communications connector that are connected to the controller’s ground plane. For RS485 operation: Install the jumper shunt across the two pins closest to the J3 silk screen. For RS232 operation: Install the jumper shunt across the two pins closest to the crystal (the default configuration). The status of a device as master or slave determines how the various pins must be configured. Also, in the diagram, the master’s /SS (slave select) is configured as an output. The receiver input has a fail-safe feature that guarantees logic high output if the input is open circuit. The driver is limited for short-circuit current and the driver outputs can be placed at a high impedance state through the thermal shutdown circuit.

This cable is usually 24AWG. Category-5 cable will generally work well in most instances even though its characteristic impedance is 100 Ohms. In general RS485 is designed for multi-drop, "daisy-chain" operation over a single twisted pair cable with a nominal characteristic impedance of 120 Ohms. We can gain insight into the operation of the RS232 protocol by examining the signal connections used for the primary serial port in Table 11 5. The transmit and receive data signals carry the messages being communicated between the QVGA Controller and the PC or terminal. Given the availability of ready-made communications cables, it is not necessary to study or understand the following descriptions of cable connections. The advantage of such a multi-drop RS-232 network is that the communications are full duplex, with each communicating party capable of simultaneous transmission and reception of data. This cable structure helps maintain stable data transmission in electrically noisy environments. Many terminals and PCs, however, do rely on hardware handshaking to determine when the other party (in this case the QVGA Controller) is ready to accept data. The entire daisy chain network is ultimately connected to a PLC (Programmable Logic Controller), facilitating data exchange between multiple devices and the central control system.

Only end devices will have a single pair of wires terminated into the communication connector, except for necessary End of Line (EOL) terminators or bias circuits. While RS422 is comparable to RS485, it is limited to unidirectional data traffic, and is terminated only on the end of the line opposite the transmitter. While RS485 is a 2-wire standard, it does offer 32 nodes on a network, on the other hand RS422 (a 4-wire standard) only specifies up to 10 nodes. While handshaking is still with us, it is usually best to disable it in software (if possible) and/or "loop-back" the pairs of signals (RTS to CTS, DTR to DSR, etc.) While RS232 was rumored to be on the "way out" with the advent of many of the new communications standards, it is still alive and well today. The primary and secondary serial communications ports are accessible through the QVGA Controller's 10 pin, dual row Communications Connector (H14) and through the individual Serial 1 and Serial 2 connectors. These standard 9-pin serial connectors are located on the top edge of the QVGA Controller.

Most computers conform to IBM PC AT-compatible RS232 interfaces which use 9-pin D-Type connectors, consequently the QVGA Controller brings out its serial ports to two female 9-pin D-Type connectors. It also has onboard LEDs to display the current state of the chip i.e. whether the chip is powered or its transmitting or receiving data making it easier to debug and use. They have Shielding Jacket over the insulation layer to protect against the Electromagnetic Interference and also each pair of wires is twisted together to prevent any current loop formation and thus much better protection against the noise. The receiver load impedence is 12K ohms (or higher) and transmitter "leakage" current is ±100µA (or less) in either the powered or unpowered state. 12V. A driver in the high impedence (off) state is able to remain in this state over the common mode range, what is rs485 cable whether power is applied or not. The main reason behind using these Ethernet Cables over normal wires is that they provide much better protection against noise creeping in and distortion of the signal over high distances. Connect the shielding net to the main communication wire shielding and then ground it.