PineNote Development/UART
This page contains information on creating and using a UART dongle for the PineNote. The PineNote was shipped with a compatible UART dongle, but replacements are not available to order in case of loss or hardware fault. Thankfully it is not difficult to make your own from easily-acquired components.
A PineNote UART dongle enables you to:
- Interact with the system boot menu
- Read system events in real time as the PineNote is used
- Fix the PineNote without opening the case if something goes wrong while flashing it
Since the PineNote is an embedded system, interfacing with it during boot is more complicated than with an ordinary computer. The UART dongle enables you to do this.
Creating your own UART dongle
A PineNote UART dongle has three components:
- A USB-C breakout board with a male connector to expose the 24 pins of the PineNote's female USB-C port (located on the bottom of the device)
- A USB-UART adapter, to plug into a USB port of the computer you'll use to interface with the PineNote
- Jump wires to connect specific breakout board pins to pins on the USB-UART adapter
The PineNote's internal UART system is documented in this schematic.
USB-C pins are documented on the USB-C Wikipedia page; of the 24 pins, two are designated for "side band" use.
These pins are labeled SBU1 (A8) and SBU2 (B8).
In the PineNote UART schematic you can see (on the bottom right diagram) these pins are given the label UART2_TX_SUB1 and UART2_RX_SUB2 respectively.
The first (TX) is used for transmitting data and the second (RX) is used for receiving data, from the perspective of the PineNote.