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Serial interface parts

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DSGarcia

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I am looking for an RS-232 driver (2 lines) as well as an RS422/485 receiver (only need one port). Supply voltage is 5VDC.

There appears to be so many parts and options; I would like to know what are the common parts.

I would like to avoid parts that require external charge pump capacitors if possible.
Thanks,
Dale
 
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For RS232, you can use the (DM)1488/1489. But it requires +/-12V.
For RS422, the 75176 is a handy part.

All of these are old technology, and cheap. You didn't mention price, availability, so I just picked the old standards.

If you can tolerate relaxed RS232 voltage levels, the LTC1387 will do both jobs in one package.
 
MAX232 is what I use. Dual driver/receiver for RS232. Uses +5 volt supply only, and then uses charge pump capacitors to get the 232 line voltages it needs. If you are in the US you can get free samples from TI. Available both in DIP and SOIC.

https://focus.ti.com/docs/prod/folders/print/max232.html

Scroll down for the example circuit, it is very simple. 25V 1uF ceramics will satisfy for all the capacitors you need.
 
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APPLICATION NOTE 882 RS-232 Features Explained

They have various version that use .1 uF caps. Not cap free but the .1uF are small and inexpensive.

The MAX202 can be had here. You can also get version with ESD protection and lower power needs but these advanced features come at a price.

I seem to recall having seen devices that do not require caps but do not know where. May be wrong about that.
 
We really need to know the full application, there may be no need for a MAX232 or similar? - something as simple as a single resistor may be all that's required?.
 
Nigel,
I think I have the information I need now, but since you asked, I will try to explain my task (and to perhaps simplify my solution a little).

Originally, I posted a question about converting RS-422/485 to RS-232 here: https://www.electro-tech-online.com/threads/rs-422-485-to-rs-232.29341/

I really did not understand the solution because the voltage specifications between the two standards did make sense to me with the proposed solutions.

Anyhow, I now have a new twist on the specifications that changed the problem. My single board computer has one RS 422/485 port available. I now need to communicate with two different serial (RS-232) devices (one at a time), but only need to transmit data.

My thought was to convert the RS 422/485 output from the SBC to digital logic. Using a couple of AND gates, I can then route the digital signal into the input of one of two RS-232 drivers.

Currently, I am thinking of using the MAX202 or 232, the SN65176, and a 74HC08 AND chip to select between the two RS-232 drivers.

I suspect that a diode and resistor may handle the conversion from the RS-422/485 port to the input of my AND gates but I am still not smart enough to know how to do this. Perhaps you can make a suggestion for this.

Thanks,
Dale
 
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