USB to UART serial converter.

[HellasTechn]

i am exercising the best tactic to destroy a topic .

Sorry for that people.

 

[CDRIVE]

Oh,
He absolutely has the sand alone chip,that is what's on the module( #69).
It connects directly to USB and produces CMOS(TTL compatible) interface to the "rs-232 side".
From #73 you can confirm that the levels are 0-3.5v.
That isn't RS-232 compatible thus a rs-232 transceiver is absolutely needed !

Somewhere in this exceedingly lengthy thread something was said by Constantine that implied or possibly stated that this is one way communication from a PC to a uC. If so I see no need for RS232 voltage levels. A USB/TTL board (The Link he posted) should fill the bill.

Chris

 

[dorke]

Somewhere in this exceedingly lengthy thread something was said by Constantine that implied or possibly stated that this is one way communication from a PC to a uC. If so I see no need for RS232 voltage levels. A USB/TTL board (The Link he posted) should fill the bill.

Chris

Not so simple,
The TTL input will be smoked by the levels of the RS-232 voltages especially the negative voltage.
A double clamp should be implemented to +VCC and GND to prevent that destruction.

 

[CDRIVE]

Not so simple,
The TTL input will be smoked by the levels of the RS-232 voltages especially the negative voltage.
A double clamp should be implemented to +VCC and GND to prevent that destruction.

You're talking Apples. I'm talking Pears. What RS232 levels?? There are none in this scenario. That USB/TTL board never sees RS232 (+ -) voltage levels. It's a virtual (USB) serial port with CMOSTTL outputs only... There's no RS232 or TTL Inputs whatsoever. It's a one direction Output device. It's outputs are totally compatible to drive the serial input ports of a uC. I also gave Constantine a Common Base level up shifter if he needs to jack the +3.3V up to +5V.
Did you read my previous reply?

Chris

Correction: It is a USB/TTL bidirectional device but that doesn't change the fact RS232 voltages are non existent.

 

[dorke]

Chris,
This thread has become a spaghetti bowl...
I didn't go through each and every post.
If what you are describing is indeed the case then there is no problem.

But still,
One has to ask about the distance between the PC and the uC board.
For a very short distance say 1meter or so ,it will work.

Not so for longer distances.
If a longer distance is needed rs-232 (or other comm signal) should be used.

 

[Harald Kapp]

The serial resistors limit the input current.
However, in order to prevent the MAX232 from operating from RS232 power they need to be fairly high. On the other hand the input resistance of the MAX232 can be as low as 3 kΩ (datasheet, chapter 7.7). Therefore the series resistors need to be fairly low for correct operation of the MAX232 on both driver and receiver side. This is a contradiction. You may get the circuit working with the series resistors but reliability will not be as good as you'd probably expect.
The transistor circuit shown by Chris in post #61 doesn't have this issue.

Probably because EB is unaware that you've shifted this thread from the MAX232 to a CP2102.

The MAX232 is a physical level converter (TTL<>RS232) whereas the CP2012 is a logical level converter (USB<>UART). These are completely different items.

It is just that i didnt want to make an other thread about rs232

You should have done. Things are getting a bit confused now, it seems.

 

[CDRIVE]

I asked Constantine to open a new thread, then I will move posts #68++ there.
I hope this will sort out things a bit.

Uh-Oh. Post 68! It would appear that it was non other than me that derailed the train and caused this sloppy mess!
Your Honor, I ask mercy from the court because this thread is not Constantine's first battle with MAX232, 3232 chips. He's been battling with them in other threads too. In my defense I thought a 'No Contact' protection order was long overdue.
Chris

 

[HellasTechn]

I'm going crazy! Anyone wanna come?

It would appear that it was non other than me that derailed the train and caused this sloppy mess!

Thank you so so much sir Chris for all the effort you have put to pass me knowledge about rs232 and more...

Your assistance is highly appreciated.

 

[HellasTechn]

Thank you Dorke, Harald kapp, Electrobrains and all people who posted here to my assistance !
I really need and ask for your help and welcome it !

 

[HellasTechn]

Anyway, after connecting it to a pc usb port and transmitting characters the Oscilloscope revealed that the output of the chip is the pin marked as TXD... so the TXD should connect to the RXD of the receiver board or whatever it is that needs the serial from the converter.