simplest way to switch from rs485 to rs232 circuit

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#1
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I have an atmel chip uart connected to a MAX3485 chip which outputs differential RS485 signal...I want to be able to make the output available from my device easily convertible from RS485 to RS232.

For example if the user wants to use the port as RS232 all he has to do is remove say 2 jumpers or rearrange them and bang he has RS232 interface instead of RS485.

I am trying to think what would be the simplest way of doing this. :shock:

Any idea?

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Linear Tech makes some combo RS232/RS485 chips. I think that the old AppleTalk interface used these. The network was basically RS485 but was ground-centered and you could use one side for RS232, quite effectively, No jumpers.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Ah yes I found some of those ISL3330 and ISL3331 and then some LCT28xx series...
I realised after I posted here that just merely bypsassing the micro usart to the user access ports will not solve the problem...hence the jumper option not possible as the output from micro is in 0-3.3V format...its needs to be true RS232 signal levels....hence looks like those dual mode chips above. Thanks...think for now I will just keep my circuit simple and only implement RS485... :)

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There are chips that do 3.3V to rs232.

Imagecraft compiler user

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In fact LT has a nifty 1.7V RS232 chip with a very simple switch-mode converter to generate more than +5V and a standard charge-pump to make -5V. Semi-spendy but to get real RS232 out of a sub-2V system, its fantastic.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!