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38

It signifies nothing; it's part of a sequential list of EIA standards: -


28

It's the document serial number of the standard. Same reason why the HTTP protocol is also known as RFC2616 and the Javascript programming language is also known as ECMA262. The numbers themselves have no meaning. For example while EIA232 specifies the electrical characteristics of a digital serial communications system, EIA222 specifies standards for ...


12

RS-422 and RS-485 use the same electrical interface specification. If you use that interface to build a bidirectional link on a single pair of wires, it's called RS-485, and it supports half-duplex operation. If you use that interface to build two unidirectional links on two pairs of wires, it's called RS-422, and it supports full-duplex operation. This is ...


8

Personally I wouldn't go for either RS422 or 1-wire. RS422 is really a point-to-point connection, like RS232 (and is usually used to extend RS232), and 1-wire is really only for local connections within a PCB. Instead you should use RS485. RS485 is like RS422 (RS232 with differential signalling), except it's designed to be point-to-multipoint, or fully ...


6

The problem is almost certainly in the USB buffering related to the USB-RS422 converter. USB has variable and fairly high latency. The easiest solution would just be a better RS422 interface, ideally something PCI/PCI-e based. That would solve the latency issues. You may also be able to modify the USB polling rate, though this is fairly dependent on the ...


5

On an open end, a short pulse will be reflected and travel back the line. On a shorted end, a short pulse will also be reflected, but inverted, too. A resistor dampens this effect, i.e. the amplitude of the reflected signal will be smaller. And for a certain value, the pulse will not be reflected at all. This is the value used for termination. Usually, ...


4

RS-422 & RS-485 are similar in that they both use balanced, differential signalling. All of the RS-422 & RS-485 systems that I have seen or worked with use 5V levels. A RS-422 driver is an output-only device. It will happily feed a RS-485 device so long as that RS-485 device is only ever receiving data. You will have a data collision if the RS-...


4

Isolating RS-485 lines is a good idea since they tend to go long distances and you want to avoid ground loops. You are right, it doesn't really matter where exactly the isolation occurs. That decision is part of the system-level design, with no one right universal answer. Sometimes it's easiest to isolate directly at the RS-485 bus. That simplifies the ...


4

In short: A ground is not needed, because of RS485's characteristics. Isolation is in most cases best. TIA/EIA 485 specifies that no more than ±7V of potential between the grounds of two separate devices (shown as GPD below). The correct method for designing a differential data link is without ground wires. For ground potential differences higher than ...


4

When you send a high speed signal down a cable, the current that initially flows is dictated by the voltage applied AND the characteristic impedance of the cable. For the types of cable recommended for RS485 and RS422, the cable characteristic impedance is circa 100 ohms. So if 1 volt is applied at the sending end an initial current of 10 mA flows and all ...


3

What you describe could be made to work, but each slave would have to be able to enable and disable driving the one return bus, and that bus would need to passively float to the idle level. RS-422 is not intended for this. Since the master is only either transmitting or receiving at any one time, you might as well use a single RS-485 bus. It doesn't seem ...


3

The answer, as found in some random documentation checked into GitHub, is: RS485 flow control (Driver enable feature) handling is possible through the following procedure: # Program the Baud rate, Word length = 8 bits, Stop bits, Parity, Transmitter/Receiver modes and hardware flow control values using the USART_Init() function. ...


3

You need to interface the RS422 properly to the Arduino. There are special chips that do this for you. Just like you would use a MAX232 (or similar) to interface the Arduino to an RS232 system, you need to shift the voltages to the right levels, and create or combine the differential pairs. Maxim (the makers of the MAX232 chip) make a number of chips for ...


3

RS-422 is a point to point communication connection. You can build it with one pair of wires to allow unidirectional communication between two parties (simplex, rarely used). With two pairs of wire it allows for bidirectional, duplex communication. RS-485 is a bus structured communication setup that can potentially support multi master communication. It ...


3

Most Professional broadcast equipment will use a D-Sub9 with the standard set by Sony: 7 - TX+ 2 - TX- 6 - GND 3 - RX+ 8 - RX- 4 - GND The above pinout is for a "Controlled" device such as a VTR. (for a "Controlling" device, TX becomes RX and vice versa). But as the other contributors have said, you always need to check with the manufacturer. And ...


3

What I would probably do is multiplex the serial data into a new serial datastream at higer rate, with a static interleave. Then feed the datastream through USB-UART to the computer. That way you would know that the first byte is from device 1, the second byte from device 2, the third byte from device 3 and in this case a fourth byte as CRC or sequence ...


3

If I understand the question, what this comes down to is taking time/place messages from GPS over one serial line, and correlating range data messages received over other serial lines. Ideally, the range finder messages would have their own time stamp, and if you could synchronize all the clocks, you'd be able to pin down the location where the range was ...


3

I think I can "piece together" your problem now. I am using the above system In your update, you seem to refer to the LTC2863 pinout. Therefore much of the confusion was that you originally mentioned in a (broken) link, that you were using the LTC2862 not the LTC2863. :-( Assuming you really did mean LTC2863, then: I am using the LTC2863 which has ...


3

If the resistor is too large, you will get incomplete damping of the fast edges of the signal, resulting in increased "ringing" and longer settling times. This recent question mentions a way of estimating this graphically.


3

RS = recommended standard RFC = request for comment, numbers don't have any real meaning


3

All of your parts will "work", in the sense that they will allow simple communication between the encoder and your Arduino. They will not, however, do what you want. The labels on the encoder lines establish that they are quadrature encoded with a home line which will become active once per revolution. This is not serial communication in the same sense as, ...


3

To answer this I need to explain a few things. (TL;DR? See Consequences below.) Voltages There are a number of different serial hardware solutions, to solve different problems. TTL: The Arduino's serial connection (TX and RX) are at "TTL levels", which means 0-5V. RX needs to be within this range to be detected, and TX will only be 0 or 5 volts - ...


3

So, your A and ~A form a differential pair – and as it's only required that the relative voltage of these reflect the data signal, a totally legal differential signal would fix A at 6 V, and make ~A alternate between 4.5 V and 7.5V (if you're going for a 1.5V differential voltage). AC coupling might also be part of the line driver - if the protocol ensures ...


3

Basically the standard defines it, by specifying how much a single receiving unit can load the bus (with resistance and capacitance), and how much load on a singly-terminated bus a single driving unit must be able to drive. The numbers are just selected so that a standard driver can drive a singly-terminated bus with ten standard receivers. Sometimes modern ...


2

A design I have used for a while now and that seems to work very well, is to use TI ISO7221A for UART (TTL) isolation, and then a driver on the nonisolated side, i.e. MCU->ISO7221->driver. I use this with an FTDI FT231 virtual serial driver, but if you prefer bare RS232 you can just use a MAX3232 instead. The advantage of this design is that it is a fair ...


2

The Due, which is really a Atmel AT91SAM3X8E, only has 4 full hardware serial interfaces (though there is an additional UART which may work). The first thing I'd strongly reccomend is to stop thinking of the board as an "Arduino". The Arduino tools just paper over the actual device. It's a AT91SAM3X8E dev board. That said, the first place to start is to ...


2

In some applications, common-mode voltage bears zero (or nearly zero) significance. For example, and RS422 driver can drive (at the far end) an optoisolator. Since the only load on the twisted pair is the LED in the optoisolator, common-mode voltage need only be held lower than enough to arc across the PC board... one might get 240VAC common-mode induced ...


2

In normal serial communications links, you actually need two wires - one is the signal and one is the ground. The ground stays at zero volts and the signal wire swings between 2 voltages that represent data bits 0 and 1 respectively (in RS232, the signal swings between +25 volt and -25 volts). Using voltage to signal is not great for long wires going though ...


2

You could AC-terminate the pair, as described in this application note, but take care to read the caveats. @Ignacio's suggestion of using a polyfuse as part of the termination resistor might be a better general solution.


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