The microcontroller boards that are used in Polish Universities are all equipped with (external - note for Majid) RS485 chips.
On Wed, Apr 21, 2021 at 4:54 PM Rob CJ <[email protected]> wrote: > Hi Majid, > > Please use Google to find out what RS485 and IIC is. Use the Jallib group > for issues with libraries and the compiler not for general questions that > you can easily find on the internet. > > Thanks. > > Kind regards, > > Rob > > ------------------------------ > *Van:* [email protected] <[email protected]> namens majid > ebru <[email protected]> > *Verzonden:* woensdag 21 april 2021 15:47 > *Aan:* jallib <[email protected]> > *Onderwerp:* Re: NT: [jallib] How to send & receive data over medium > distance > > RS485 is very powerful. > > But I don't how to implement in PIC?!? > > Is i2c the same rs485?! > > On Wednesday, April 21, 2021 at 4:41:19 PM UTC+4:30 vasile wrote: > > At 15m and 5V there is no problem with data sent in current. Using twisted > wire cable is a good habit. > From the EMI perspective twisted cable it is about half as good as a > shielded cable and has the parasitic capacity quite low compared with the > shielded cable. > RS485 (standard 32 loads) is feasible at 1Km and quite high speed. Still > there is an issue with the ground line and requires good terminators. > Data goes either on A&B plus ground cable (three wires between Tx and RX) > or just A&B (two wire cable) and ground connected to earth on the > transmitter and receiver end. > In the last configuration an issue is quite frequent caused by an offset > (variable ground potential between TX and RX). > Also lightning is a problem for outdoor cables...and nothing help... :)... > no matter how others will convince you to put three tranzorbs on each TX > and RX end. > happy communications! > > > On Wed, Apr 21, 2021 at 8:32 AM 'Oliver Seitz' via jallib < > [email protected]> wrote: > > Thanks for the additional information, 800m is something very different > from 20m ;-) > > I can imagine that 20m at 5V ground-referenced is doable, but when you're > starting, better stick to the specifications and try your luck when you > have a bit of experience. > > I myself am at a similar project, like 15 meter, and I want to use as > little standby current as possible, and no twisted pairs. It's > uni-directional, with constant-current pullup at the receiver and optically > isolated pulldown at the sender with 1200 baud... First test of the concept > in a few days ;-) > > If standby current was of no concern, I'd use RS422 or RS485 > drivers/receivers, true RS232 is old-fashioned and needs to many components. > > > Greets, > Kiste > > Am Mittwoch, 21. April 2021, 07:02:46 MESZ hat vsurducan < > [email protected]> Folgendes geschrieben: > > > > > > Oliver, I remember the problems I had with an EIA232 with +/-8V output > running at 800m at 9600bps. Everything works until due the transceiver > heating the voltage dropped at +/-7.6V...:) > The length is given by the voltage at the level converter of the > transmitter output. All level converters with charge pumps are not able to > give more than +/-8V...+/-10V in the happiest circumstances. > Oldest/goldest EIA232 worked at +/-25V up to 2km. > For 20m you do noy need any level converter at the output of your PIC, > just a twisted pair RX-GND TX-GND (CAT5 ethernet cable is perfect) and an > open collector transmitter ( a gate) with pull-up resistor in the receiver > end (at 20m distance from the transmitter). > However Majid, I think you need first to learn jal and for that there is > a learning curve which has to be passed.... > Please start with the examples, compile them, make them run, modify them > as you wish and post only when nothing works for you after three days of > trying...this will help you more than you may believe right now... > best wishes > > On Wed, Apr 21, 2021 at 7:28 AM 'Oliver Seitz' via jallib < > [email protected]> wrote: > > Hi Majid, > > > > SPI is designed for centimeters, I don't think it can work reliably over > 20 meters. > > > > RS232 at 9600 baud is ok for 150 meters, if you're using real RS232 > drivers and receivers like from the MAX232 series. The PIC controller does > not have RS232, it has a usart which handles the NRZ protocol. This > protocol is best known as being used by the RS232 interface. Therefore the > protocol itself is commonly (but wrongly) referred to as "RS232" > > > > RS232 uses negative voltages as a symbolic "1" and positive voltages for > "0". At the receiving side, the voltage must at least go higher than +3V > for "0" and lower than -3V for "1". At the sending side, voltages from up > to +15V and down to -15V are used. > > > > So, to answer your question in two simple sentences: RS232 is ok for the > job. But RS232 is not what comes out of the controller. > > > > Greets, > > Kiste > > > > > > > > > > Am Dienstag, 20. April 2021, 21:56:34 MESZ hat majid ebru < > [email protected]> Folgendes geschrieben: > > > > > > > > > > > > can i ask another question?? > > > > if it is 20 meter distance between PICs , i should use RS232 or SPI? > > > > so sorry and thanks a lot > > > > majid ebru در تاریخ سهشنبه ۲۰ آوریل ۲۰۲۱ ساعت > > > > -- > > You received this message because you are subscribed to the Google > Groups "jallib" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected]. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/jallib/1697687282.4677348.1618979276333%40mail.yahoo.com > . > > > > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/jallib/CAM%2Bj4qtaBjojssk_HHFK1M2dhhL9CNNf3mygd1F3nH0B5bck9A%40mail.gmail.com > . > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/jallib/1020737915.4719521.1618983169979%40mail.yahoo.com > . > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/jallib/22c899b2-b475-404d-9982-fb4e9ffe3169n%40googlegroups.com > <https://groups.google.com/d/msgid/jallib/22c899b2-b475-404d-9982-fb4e9ffe3169n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "jallib" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/jallib/AM0PR07MB624188EEE1255C4E45C31F80E6479%40AM0PR07MB6241.eurprd07.prod.outlook.com > <https://groups.google.com/d/msgid/jallib/AM0PR07MB624188EEE1255C4E45C31F80E6479%40AM0PR07MB6241.eurprd07.prod.outlook.com?utm_medium=email&utm_source=footer> > . > -- Vasi -- You received this message because you are subscribed to the Google Groups "jallib" group. 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