Update README.md

Add reference to picoprobe.

uart/terminal/README.md

@@ -1,7 +1,7 @@
 # Pico serial terminal
 
 A simple example to allow a Pico to act as a serial terminal into another Raspberry Pi computer.
-Usefull for setting up a Pi when network setup fails for some reason.
+Useful for setting up a Pi when network setup fails for some reason.
 Should work for Windows, Linux, or Mac host machines.
 
 1. Add `enable_uart=1` to the Raspberry Pi computer `config.txt` and boot it.
@@ -13,8 +13,13 @@ Should work for Windows, Linux, or Mac host machines.
 
 You should now have a serial terminal to your Raspberry Pi computer through your Pico.
 
-### Erratta / Bugs
+### Errata / Bugs
 
 * Input is only taken a whole line at a time after the EOL character.
 * Line input is ALWAYS echoed back to the terminal as a new line, even passwords
 * Control characters are dropped so no curses tools (like `raspi-config`) work
+
+For a full-fledged serial interface, look at [picoprobe][probe] referenced in Appendix A of the [Pico Getting Started Guide][get-start].
+
+[get-start]: https://datasheets.raspberrypi.com/pico/getting-started-with-pico.pdf#page=61
+[probe]: https://github.com/raspberrypi/picoprobe/