One of the very useful things to own when dealing with embedded computers is a low-voltage&#x2F;CMOS usb-to-serial cable, such as this one: <a href="https:&#x2F;&#x2F;www.adafruit.com&#x2F;products&#x2F;954" rel="nofollow">https:&#x2F;&#x2F;www.adafruit.com&#x2F;products&#x2F;954</a><p>There are modules that have variable I&#x2F;O voltage, very handy when dealing with devices that have 1,8V, 2.5V, 3.3V or 5V logic: <a href="https:&#x2F;&#x2F;www.sparkfun.com&#x2F;products&#x2F;12731" rel="nofollow">https:&#x2F;&#x2F;www.sparkfun.com&#x2F;products&#x2F;12731</a><p>Equipped with such a cable, you can also observe any errors that might occur on bootup, such as when you have made a mistake in configuring your config files on the filesystem.<p>For normal &quot;Rasperry Pi&quot;-Level work, the cheapest eBay-cable will probably be ok. If you have more exotic devices you&#x27;ll appreciate UARTs that can produce almost arbitrary baudrates, or might support inverted Tx&#x2F;Rx pins. I found some chinese knockoffs using a &quot;CH310&quot; UART&#x2F;i2c&#x2F;spi chip to be particularly broken.<p>(EDIT: Added last paragraph, fixed a few typos)