UART to RS-232

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UART to RS-232

Unread postby Motozoic » Fri Jul 06, 2018 9:22 am

I've got a couple of questions, hoping I can get some help here:

  • I understand that my XU4S has a 1.8V TTL UART exposed on the 4-pin Molex connector, but does anyone have the pinout for this connector?
  • I need to interface the UART to an RS-232 connection on an external device. Does anyone know if there is an RS-232 transceiver that will work for the 1.8V TTL level UART in this case? I've used the MAX232 chip before, but the datasheet says that the minimum TTL voltage must be 3.0V. I was looking at this Linear device and it looks like it might work for 1.8V TTL? https://www.digikey.com/product-detail/ ... ND/1620314
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Re: UART to RS-232

Unread postby odroid » Fri Jul 06, 2018 9:57 am

4pin pinout is available in this wiki page.
https://wiki.odroid.com/accessory/devel ... _connector
But the 4pin /dev/ttySAC2 is assigned to the system console IO.

So you have to use another UART /dev/ttySAC0 in 30pin header for general purpose communication.
https://wiki.odroid.com/odroid-xu4/appl ... /gpio/uart

The Linear device seems to be fine.
Or, use a cheap level shifter board with a normal MAX232 something like this.
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Re: UART to RS-232

Unread postby Motozoic » Fri Jul 06, 2018 11:08 am

Thanks for the response.

Unfortunately however, I am using an XU4S (HC1), which does not appear to have any headers exposed. Would it be safe to say that implementing a serial port for custom purposes is not possible on this board?
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Re: UART to RS-232

Unread postby tobetter » Fri Jul 06, 2018 12:05 pm

Motozoic wrote:Thanks for the response.

Unfortunately however, I am using an XU4S (HC1), which does not appear to have any headers exposed. Would it be safe to say that implementing a serial port for custom purposes is not possible on this board?

I guess you would be able to use the UART for the generic serial port if you give up a console through the same port and can make SSH connection through the network. You will need to change the kernel command line to set the console to another one. Another option is to add USB-to-UART dongle.
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Re: UART to RS-232

Unread postby mad_ady » Fri Jul 06, 2018 2:11 pm

There's a guide on how to turn the serial port into a general purpose serial port on the wiki. You also need to recompile uboot and have it use the other, unexposed serial port.
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Re: UART to RS-232

Unread postby odroid » Sat Jul 07, 2018 7:15 pm

Right. I forgot this nice wiki page.
https://wiki.odroid.com/odroid-xu4/trou ... le_console
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Re: UART to RS-232

Unread postby Motozoic » Wed Jul 11, 2018 3:08 am

Thanks for providing that link... I'll give it a shot and see where I end up!
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