Serial Communication RS232 & RS485 

Real talk

I thought about the very same thing and was 100% sure the first comment was gonna be something about that

You are welcome!

Glad it was helpful!

You are welcome!

Yep! You are correct!

so you know now how to program such a connection

@@Cien_Swiatla when I was in school I knew! Now I forgot

@ :-)

Late to the party here, I know. The difference has to do with noise sensitivity. Look up the term "common mode rejection".

Shjdbbsjxhbsjdhdhsihshdihdhdjhxjjxhsisbdhkdhdbdihshdhudhdhdhhsudhshishshidhshdihdhdjjxhdhdjhdhdjhsjshixhhv

Hsjsjhsudjhdhduhdhdihsishdidhhxjdhdhhxhxhjxhshjdhdjdhjxjxudhhsijdjxjjxjxjuxjjdjdjjdjdhdhbsjshshiehevidhdushsuhzu

Jsjshjdjhhsihudijdbddhjdhshidhsbishshidvsidhhsisbshixbdjdjjdhdhdjhdhdhjdhdhjdjdjdjjdjdhdhdihdhdihdhdihxjdjdjjxhhxdjhdkdjkdjdjdjjdjdjdjjxjxjxhxh

Djhsidhdjixjdjhsishhishdhidhdihdhdbdbdkdbjdbdjdjjdhsuhxhxhddhhdhdhduhzhdusuuxuuhxjdjidjxjxjdhhdjdhdihxjdhdhg

Jdhshsishidhsisjjddhdjshhdhdhxhhshzhhxhxhxhhxudhxhhxhshxhhxhxhixhhdihdhdihxhxiuxhxhhxjxhhdhdhdhsvidhdihh

No. The 120 ohm resistor is a termination that absorbs the signal to prevent it from reflecting back to the source. If allowed to reflect back to the source, the signal will either add to or subtract from signal coming from the source. A 120ohm resistor is placed a both ends (Rx and Tx). Doing matches matches impedance at both ends.

on rs 232 there is no voltage induced in 2nd wire because that was ground...even if any voltage is induced that will be send to ground any ways in 485 the signal is taken from an opamp (you can consider it as an opamp they are actully driver circuit which works some what like opamp) on both side so difference in signal is taken at last in rs 485 opamp is switched from receiving to transmitting mode when needed

You probably dont give a damn but does anyone know a tool to log back into an Instagram account?? I somehow lost my password. I appreciate any help you can offer me.

@Tyler Micah instablaster ;)

@Dennis Alfred I really appreciate your reply. I got to the site on google and im trying it out now. I see it takes a while so I will reply here later when my account password hopefully is recovered.

@Dennis Alfred it worked and I finally got access to my account again. I am so happy! Thanks so much you saved my account!

@Tyler Micah happy to help =)

Federico Pinto i2c which is rs232 uses clock and data, and tx and rx which is rs485 so they're different

as far as i Can think ...ground never becomes high. So there is no high state in ground wire which should get effected by noise. And as we know the ground is reference in 232 , the refrence remains stable in 232 with respect to data cable which gets affected by noise leading to error in data loging whereas there is no reference in 485 , no refernece means no comparison. Again thats as far as i can think. Hehe . Hope soemone guides me too if i am wrong. Thanks.

Do you mean after the transmitting device finnshs sending a message and the receiving device then transmits an acknowledge back but before the receiving device turns its driver around again to get ready for the next message, the transmitting device is already sending data? If so, you need to adjust a parameter sometimes called "Tx delay" on the device that's switching too fast for the slower device. Hope that makes sense in layman's words. But before this make sure both ends are using the same baud rate settings.

Multi point in enineering terms. Out in he field we say multi drop only as a trade buzz word.

Kriti is correct. he is actually talking about RS422, RS422 is a multidrop protocol and RS485 is a multipoint protocol.... not a buzz word but slightly different protocols.

RS485 allows for multiple devices to either transmit or receive, depending on their unique device ID that gets sent out by the master device. RS485 is definitely a multi point protocol.

Means the same thing, multi drop, multi point.

megaspeed2v2 why is the resistance of "ground" any less than the resistance of the wires carrying the other signals? Are the wires carrying the transmission signals and the ground wire not the same thickness and roughly the same length? Separately, assuming the ground wire is a much lower resistance than the wires carrying the transmission signals, why would that cause the chip to be unable to see any induced voltage (noise)? Would not the only difference caused by having a much smaller resistance wire be a larger current?

+megaspeed2v2 When you say "ground," you are referencing the ground plane of the PCB right? The chip is not connected to physical earth ground through a water pipe or something like in the main breaker in a house, correct? So you seem to be saying that the resistance between the ground wire and the ground plane is very low. If there is an induced voltage on the ground wire, would it not make its way to the ground plane? If the induced voltage makes its way to the ground plane, and the ground pin of the chip is connected to the ground plane, and the chip uses the GND pin as a 0v reference, would that reference not be shifted by the induced voltage?

***** maybe ive said something wrong in my previous comments so can i start again. The noise may be induced onto the ground wire but that noise is pulled to ground since the other side of the connection is on ground which is ALWAYS 0v relative to any pin on the chip even if noise gets on the wire that wire will be at 0v while the signal wire will still be at 0.1vp-p for example if there were 0.1vp-p of noise so the noise isnt removed from the resulting signal. For noise removal to be done, the signal has to be send along with another copy of itself on a second input wire, difference being that the copy is 180 degree phase shifted before being sent along its way, (what happens if you add those two together? you get an output of 0v as the 180 degree shifted signal cancels the original but however, once the signal from each output reaches the input of the next device that device then shifts the one signal back to its original phase, the point of this is that noise adds itself in after the first phase shift and before the second one so when that second shift is done, the noise on the second wire will be 180 degrees out of phase with the noise on the first wire and so cancels eachother out whereas the signals on each of the two cables are returned to in-phase with eachother so the pass through unharmed. ^i guess you can see by my wall of text why he simplified the explanation in the video xD

megaspeed2v2 Thank you for your responses, but with all do respect I don't believe you have addressed my question. Wouldn't the fact that the noise is pulled to ground, "which is ALWAYS 0v relative to any pin on the chip," cause a problem? If the chip expects ground to ALWAYS be 0v, but then a noise signal is pulled to ground causing it NOT TO BE 0v, would then all the readings not be off because what the chip sees as its 0v reference is actually 0.1vp-p (in your example)? Am I misrepresenting something in my scenario, or are one of the assumptions explicit in what I am saying false?

***** i did address your question, ground is always 0v relative to everything else in the system. that is your answer. any noise on the ground wire doesn't cause ground to no longer be relative 0v because if it did then it wouldn't be ground.