Soner

Test the chain in order, because each link produces a different symptom and the fixes are unrelated.

1. Is it a data cable? This is the single most common cause and the most infuriating. A large fraction of USB cables sold with devices are charge-only — power and no data lines. The board lights up, so it looks alive, and the computer never sees it. Try a cable you know carries data before anything else.

2. Does the operating system see a device at all? Look in device manager with the board plugged and unplugged. If nothing appears or disappears, it is cable, port or board power. If something appears with a warning marker, it is a driver.

3. Is there a driver for the USB-to-serial chip? Many boards use a third-party bridge chip rather than native USB, and Windows does not always ship a driver. This is what produces the port simply not existing. Install the driver for the specific chip on your board.

4. Does a port appear, and is the right one selected? Ports get renumbered between plugs.

5. Does upload succeed? Only now is it about timing, bootloaders and settings.

For step 3 specifically, since it is where most people are stuck: identify the chip before hunting a driver.

Look at the small chip near the USB connector on the board, or at the device description Windows shows. Common families each have their own driver and they are not interchangeable. Buying an inexpensive clone board very often means one of the third-party bridge chips rather than the one on the official design, and it is why the official instructions do not match what you see.

Two warnings that save an afternoon:

• Get the driver from the chip maker or the board vendor, not from a search result offering a bundled installer. This category of download is a favourite of bundlers.
• A previously installed bad driver blocks the good one. If an earlier attempt left something broken, uninstall the device and tick the option to remove the driver software, then replug.

One thing worth checking while you are there: whether the partition is actually full of kernels, or of something else.

Sort the directory by size before assuming. I have found a crash dump, a stray backup somebody wrote to the wrong path, and once an entire copy of a home directory. Deleting old kernels in that situation frees very little and you conclude the cleanup did not work.