Important RS485 Standard Smartphone Apps > 자유게시판

Each of the 24 SMINI input lines feature optional input line filtering for maximizing immunity to electrical noise frequently encountered with pulse-type command control systems such as DCC and Railcommand. Although all the I/O lines are physically on the same SMINI card it is convenient to talk about them as being separate (I/O) cards within the same (SMINI) card. It is a complete self contained node, being sort of a gee-wiz do-all type of card. Additionally, connections between nodes should be contiguous from the computer to the first node, then on to the next and then the next. When using RS232, the serial connections between the computer and SMINI are made using the 3-pin header along the top right edge of the card. I will refer to these "cards within a card" as "Cards 0 and 1" for providing the 48-outputs and as "Card 2" for providing the 24-inputs. You will find these nomenclatures used along the left, bottom and right edges of the SMINI card.

It is like the Universal Serial Bus (USB) or ethernet that we can find in many of our modern computers. RS-485 signals transmit on a serial bus, meaning all senders (masters or managers) will be detected by all receivers. The primary difference between RS-422 and RS-485 is that RS-485 requires two wires in a single pair which all devices transmitters and receivers are connected to, and RS-422 typically uses two or more pair in which only one transmitter and up to ten receivers are connected to a single pair. Many characteristics of the transmitters and receivers are the same as RS422. There are two other devices in this figure (receiver and transciever) that are connected to the transmission line the same way. In a serial interface the receiving and transmitting devices must operate at the same baud rate. LED L2 (amber) blinks when the SMINI is receiving data from the PC and L3 (red) blinks when the SMINI is sending data back to the PC.

Commercial aircraft cabins also use RS485 for low-speed data communications. Two 5-pin headers are provided for use with RS485. The fifth, or bottom pin in each RS485 header, is provided to maintain continuity for the shield normally used with RS485 cabling. The error codes have been significantly expanded over those provided with the original Classic USIC. L1 (green) blinks to show that U1’s internal program is operating correctly and also provides error codes when not operating correctly. DIP containing a Micro-Processor Unit (MPU), 8K 14-bit words of FLASH Program Memory, 368 bytes of RAM Data Memory, 256 bytes of EEPROM data memory, a Serial Communications Interface (SCI), built-in baud generator, three programmable timers, and an abundance of I/O pins. TODO: add connectors and pins from manufacturers such as NI, B&B, ADAM, etc. Volunteers? Each railroad device being interfaced simply connects directly to one or more of these pins. If more than one segment happens to be turned on, the software within the SMINI defaults to using the baud rate corresponding to the highest switch segment with an "on" setting. The cable's length, impedance, terminations, stub lengths, and data rate will all have an impact on signal quality. The use of the terms bit and byte will become second nature as you begin to put the interface to use.

This is significant because a serial interface transmits data sequentially, one bit after another, as opposed to a parallel interface, which for example might transmit one byte (eight bits) at a time. I find it easiest to think of the SMINI card as being four cards combined into one, an SUSIC combined with two 24-bit output cards and one 24-bit input card. The SMINI includes circuitry for two 24-pin output cards and one 24-pin input card. In the RS-485 standard, one wire is labeled "A" and the other is labeled "B", and the wires are twisted together (a "twisted pair"). To be on the conservative side, it is always best to use dual twisted pair shielded transmission cable for RS485. In this case your best bet for defining how long the cable can be is to try it. This electrical noise can easily couple into the RS485 cabling to create data transmission errors. On the other hand, RS-422 commonly supports full-duplex operation, allowing for simultaneous transmission and reception of data. EIA-530 and EIA-449 are standards that specify a connector, pin assignments and RS-422 electrical levels.

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