RS232 - RS422 CONVERTER

[HellasTechn]

HELLO !

I am looking for some converter that can convert rs232 to rs422 and at the same time rs422 back to rs232. In other words i need to connect the converter to my laptops rs232 serial port and exchange data between an rs422 device. Probably something that can be powered from a 5v usb port so that i dont need to carry an external power adapter and costs like 10-20 USD ?

P.S. Yes my laptop does have a serial port

Thank you !

 

[Harald Kapp]

Have you tried Google or another search engine? I get lots of hits. Although cost is typically quite a bit more than your stated goal. These adapters are usually not USB powered.
Why not use a USB <> RS422 adapter? That solves at the same time your second issue, the power suply via USB.

 

[HellasTechn]

Why not use a USB <> RS422 adapter? That solves at the same time your second issue, the power suply via USB.

Because i work on old GPS receivers and compasses that communicate via RS422 while i practice ways to interface them with microcontrollers that use rs232 (either ttl or cmos voltage levels).
Though your idea is not that bad.

One other alternative i see is for me to build such a converter with a max232 and a ds8921 chip. I could combine the typical circuit diagrams of these chips and power them with 5V from a usb.

That should be simple enough. Though i was really hoping to avoid that.

 

[AnalogKid]

https://www.ebay.com/sch/i.html?_from=R40&_nkw=RS422-RS232+converter&_sacat=0&_sop=15

https://www.ebay.com/itm/RS-232-To-...151277?hash=item2809fb3a6d:g:64EAAOSwFL9Tvfx8

I'm not wild about this device getting its operating power from the RS232 port. Sounds like it is diode OR-ing several pins together. It is a gamble, but for $12 it is a cheap gamble.

ak

 

[Minder]

The one in the second link can be had for 1/4 the price ebay 152979237575
I have used these in the past and work well, no separate power required.
M.

 

[AnalogKid]

You're right, same thing, better price. Don't know why that one didn't come up in my search.

https://www.ebay.com/itm/RS232-to-R...914970?hash=item1ed2b23bda:g:LRYAAOSwPPpaQe-K

Similar item, different company, Still can't get Minder's to come up in a general search. My kung-fu is weak.

ak

 

[Harald Kapp]

Jassu Constantine.

microcontrollers that use rs232 (either ttl or cmos voltage levels)

You led me on the wrong path by what I think is a misunderstanding on your side.
RS232 is a standard that operates on comparatively high voltage levels (+- 15 V). RS232 can be and is typically used to communicate via a UART protocol.

When you mention TTL or CMOS levels, you mean the UART interface of the microcontroller. This is not RS232! You can directly create an RS422 interface to the UART port of a microcontroller. E.g. Maxim offers few easy to use componnets that can be powered from the microcontroller's 5 V or 3.3 V supply, see here. These chips are not expensive and easy to handle. The question is whether you use full duplex (separate TxD and RxD lines) or half duplex (shared TxD/RxD line). You'll have to chose the appropriate chip and you need to make teh software fit for handling simultaneous Tx/Rx (full duplex) or alternating Tx/Rx (half duplex).

 

[Minder]

You're right, same thing, better price. Don't know why that one didn't come up in my search.
Similar item, different company, Still can't get Minder's to come up in a general search. My kung-fu is weak.

ak

All you need to do is go to Any ebay listing and substitute the 12 digit number with the the one in the listing URL and delete everything after it.
I use these for equipment that has RS485 modbus inputs from my laptop COM port.
M.

 

[AnalogKid]

All you need to do is go to Any ebay listing and substitute the 12 digit number with the the one in the listing URL and delete everything after it

I know that part. But I can't seem to hit the right combination of words to have that part come up in a general search. For example, changing from "RS232-RS422" to "RS232 to RS422" got me closer, but your part still did not come up. Not exactly the end of the world.

ak

 

[Minder]

Odd? I just entered RS232 RS485 in my search and it is at the top.
I guess RS485 makes the difference.
M.

 

[HellasTechn]

You led me on the wrong path by what I think is a misunderstanding on your side.

Okay i think i know now what the confusion is. I should have explained better.

I need the converter to to enable my laptop to receive rs422 and also transmit rs422 to devices such as GPS and compass.
Why do i need that ? because i try to figure out ways to interface microcontroller with the above rs422 devices.
The converter i am looking for is not to be used between the rs422 devices and the microcontrollers but between the rs422 devices and my laptop.

 

[HellasTechn]

Odd? I just entered RS232 RS485 in my search and it is at the top.
I guess RS485 makes the difference.
M.

Since my knowledge about serial communication is very limited, the next question that pops into my mind is this:
is the rs485 standard compatible with the rs422 ? Can i use and wire the above converter as i would with an rs232 to rs422 ?

I searched and found this:
http://www.ti.com/lit/an/slla070d/slla070d.pdf

Paragraph 2 (if i remember correctly) states that rs422 and rs485 appear to be similar but they are distinct and interchangeability
is determined by the bus architecture.

 

[AnalogKid]

For point-to-point connections (non-bused), 422 and 485 are essentially identical. 422 allows multiple receivers on one line, but only one driver. 485 allows multiple drivers and receivers on one line.

ak

 

[HellasTechn]

Thank you all !!!