Raspberry Pi Pico-Based System Identification

This project uses a Raspberry Pi Pico to identify and store various information about a system/fixture, settable and retrievable over UART or USB. Additionally, writing can be disabled by jumping GPIO pins 14 and 15 together (pins 19 and 20 on the board).

Pre-built UF2 files ready to flash onto the Pico for both USB and UART are available here.

Information Fields

There are 10 R/W information fields stored on the device. It's also possible to read the Pico's unique 64-bit identifier as a hex string, but of course this is read-only. The idea is that the Pico's serial number can always be used to uniquely identify any device, as no two Picos have the same serial.

It's worth noting that each sector (4096 bytes) of flash has a guaranteed minimum of 100,000 program-erase cycles according to the manufacturer. Each write to one of these fields will incur one erase and one program. This effectively limits us to 100,000 writes to any of these fields. Of course, the intended use of this device is to be set once and then write-locked for the rest of its lifespan, so that's likely not a huge concern here.

Field	Access	Description
MFG	Read-write	Manufacturer
NAME	Read-write	Name
VER	Read-write	Version
DATE	Read-write	Date
PART	Read-write	Part number
MFGSERIAL	Read-write	Manufacturer's custom serial number
USER1	Read-write	General-purpose field 1
USER2	Read-write	General-purpose field 2
USER3	Read-write	General-purpose field 3
USER4	Read-write	General-purpose field 4
SERIAL	Read-only	Pico's unique 64-bit serial number

Note that each of the above fields has a maximum length of 63. Each field is 64 bytes, but is null-terminated. Values longer than 63 bytes will be truncated.

Commands

Communicating with the Pico over serial is very simple. Each command must be terminated with a carriage return (\r). If a line feed (\n) is sent afterwards, it will be ignored. Use 115200 baud, no flow control, 8 bits per byte, 1 stop bit.

To set a field, send the field name, an equals sign, and the field's value. For example, to set the device's manufacturer field:

MFG=Bloomy Controls\r

To query a value, send the name of the field followed by a question mark. The Pico will respond with the value delimited by a CRLF (\r\n). For example, to query the manufacturer:

MFG?\r

There are two additional commands:

Command	Description
CLEAR	Clear all writable fields
CHECK?	Check that the data stored in flash matches the stored checksum, then return either OK or ERR

Build Requirements

You'll need Ubuntu or Debian to build this (WSL works just fine). Before attempting to build this project, install required packages using the following commands:

sudo apt update
sudo apt upgrade
sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi build-essential python3 git

Building

First, you must configure the build system:

cmake -B build

This step may take quite some time, as it will download the Pi Pico SDK. If you wish to use USB for serial communications instead of UART, add -DUSB_SERIAL=ON to the above command.

After the configuration step is done, you can build the project like so:

cmake --build build

This will generate all the outputs in the build directory. The UF2 file (used to flash the Pico) will be named pico-ident.uf2.

Installing

To install the firmware onto the pico, hold down the BOOTSEL button on the Pico while you are plugging in its USB cable. It should show up as a storage device in your file explorer. Simply drag and drop the UF2 file to it and it should unmount automatically. It's now flashed and ready to use.