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I picked up a USB serial null modem cable, so that I can connect up to a headless linux box. As a quick test, I plugged the device into the usb null modem, and the other end I connected to a windows pc. I opened up a terminal on the windows side, with 115200 8N1. On the linux side I opened minicom with the same params.

My problem is that I can type one way from the pc and see the text on the linux minicom side. If I type on the linux side it doesn't show on the pc side. If I reverse the cable it reverses the process. I bet this is a simple issue but I haven't dealt with serial comms in ages.

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Try flipping your hardware control setting (i.e. if it's XON/XOFF or Software, set it to CTS/RTS or Hardware) – LawrenceC Mar 13 '11 at 23:10

Sounds like you do not have a fully wired cable in there somewhere. If reversing the cable changes things, the CD might be clipped on one side or cross wired. If you are using the typical Cisco RJ45 to DB9 in the cable path, that will drop CD. (Very annoying when working with full PCs or single board computers that care about CD.)

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Turn off your hardware flow control.

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