So I am using an code and trying to communicate to another device using a usart. i have noticed that i must connect the transmit line of the usart to the transmit line of my rs232 level shifter to get things to display on my computer, why is this?
thank you.
Hello, The TX and RX indications are given to I/O lines following the RIAE or RS232 specifications for DB25 connectors, which are male and female (of course) and in some situations don't reflect the actual data direction, which can be confusing so tx is sometimes receiving. I think it is bi.
If you are into microcontrollers, some of them has built in TX/RCV for RS232. no need for level shiftars. RS485 is better becoauz you do not need the -12V for a logic 1.
Bye
Doesn't that require that the other side is also using RS485? The best interface is quite often the interface used by the other side...
By the way - need what -12V? Many serial interfaces for use at higher speed or longer distances needs negative voltages, unless they are using differential lines. But most trasceivers for such use has built-in voltage doublers and voltage inverters.
total gobbelygook 1) there are (as far as I know) no '51s with built in RS232 transcievers, if some exist I would liketo know. 2) there has not been a need for -12 to drive -232 for AGES, the MAX232 family has been around for a loooong time.
Erik
Is that true? You should connect + and - 12v. to the chip then, or are there switchers inside like in the Maxim 242 chips? Are you think on this?:
I haven't seen one with a built-in transceiver.
It is a bit problematic since you use a different technology when you design a microcontroller than you use for a transceiver since one is optimized for high speed and low power with digital signals, while another is optimized for high voltages and good tolerance to ESD and other abuse.
But jsut as Erik noted: Todays traceiver solutions normally generates their own voltages, to allow them to be fed from a single 3.3V or 5V power source.
Well, I've never seen a microcontroller with built-in RS232 transceivers!
Yes - the "Tx" and "Rx" names refer to the Lines - not to the pins.
So the line that carries carries "Transmit data" must clearly have an input at one end of it, and an output at the other!
Similarly for "Receive data".
Another way to make sense of it is to think that "Tx" refers to data "to be transmitted"...
Hi. if you are into microcontrollers, some of them has built in TX/RCV for RS232. no need for level shifters.<?i>
Only if you connect on logic level (ttl) you can leave out a level shifter IC (bucket device?). But then you should'nt call that RS232, because that implies using + and minus negative voltages.
So you can definitly not connect a port chip without a levelshifter (max232) to an RS232 device, cause the chip is all ttl only ever and maybe cmos sometime.