Connect to embedded device through serial, possible and how?

Question

I have a device with embedded linux. I need to access the CLI of this device, and found a RS232 port in the motherboard. Can I access CLI with putty, using this RS232 port?

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• Frog: If it’s running getty on that port then you’re in with a chance, if not then you’ll need to access the device another way and run a process that services the port one way or another.

Answer 1

The fact that a linux device has a RS232 connector does not mean you can connect to it and access a CLI console. It may still be possible if it does provide you a console.

You also don't know why it says RS232 on that connector. Maybe it does provide an actual RS232 interface. Maybe it is just a connector for a separate module that provides the level conversion between logic levels and RS232 levels.

So you need to reverse-engineer what voltages are present on the connector to determine if it is a logic level or RS232 level interface. Then you need an appropriate cable between PC and this device. Maybe resolve with an oscilloscope or logic analyzer which pin is an output, and what bit rate is used.

Then the next problem is to figure out which is the input pin.

But embedded devices may not have a console for security reasons. You might need to do something special to enable the console, or can't do anything because it is locked by the vendor. Such devices include Wlan routers running firmware specific to your ISP, even if it the stock hardware could run stock firmware.

Answer 2

Based on experience I'd say it is somewhat likely, but it is certainly not guaranteed.

Also, if you can access a console there, you may quickly end up needing a password for logging in.

• Linux Dev: may be i can find password. the only problem accessing root shell
• MiNiMe: You also needs the physical pin out, and then attach a cable to the pins / solder pads. But good luck in your quest.