feat: add unique USB serial numbers from RP2350 chip ID

faderpunk/src/main.rs

@@ -151,6 +151,9 @@ async fn main(spawner: Spawner) {
     // USB
     let usb_driver = usb::Driver::new(p.USB, Irqs);
 
+    // Read chip ID for USB serial number
+    let chip_id = embassy_rp::otp::get_chipid().unwrap_or(0);
+
     // Buttons
     let buttons = (
         p.PIN_6, p.PIN_7, p.PIN_38, p.PIN_32, p.PIN_33, p.PIN_34, p.PIN_35, p.PIN_36, p.PIN_23,
@@ -193,7 +196,7 @@ async fn main(spawner: Spawner) {
 
     tasks::i2c::start_i2c(&spawner, p.I2C0, p.PIN_21, p.PIN_20).await;
 
-    tasks::transport::start_transports(&spawner, usb_driver, uart0, uart1).await;
+    tasks::transport::start_transports(&spawner, usb_driver, uart0, uart1, chip_id).await;
 
     tasks::clock::start_clock(&spawner, aux_inputs).await;
 

faderpunk/src/tasks/transport.rs

@@ -47,9 +47,10 @@ pub async fn start_transports(
     usb_driver: usb::Driver<'static, USB>,
     uart0: UartTx<'static, Async>,
     uart1: BufferedUart,
+    chip_id: u64,
 ) {
     spawner
-        .spawn(run_transports(usb_driver, uart0, uart1))
+        .spawn(run_transports(usb_driver, uart0, uart1, chip_id))
         .unwrap();
 }
 
@@ -58,10 +59,23 @@ async fn run_transports(
     usb_driver: usb::Driver<'static, USB>,
     uart0_tx: UartTx<'static, Async>,
     uart1: BufferedUart,
+    chip_id: u64,
 ) {
+    // Convert chip ID to hex string for USB serial number
+    let mut serial_buf = [0u8; 16];
+    let chip_id_bytes = chip_id.to_be_bytes();
+    const HEX: &[u8; 16] = b"0123456789ABCDEF";
+    for (i, &byte) in chip_id_bytes.iter().enumerate() {
+        serial_buf[i * 2] = HEX[(byte >> 4) as usize];
+        serial_buf[i * 2 + 1] = HEX[(byte & 0x0F) as usize];
+    }
+    // Safety: We just filled the buffer with valid ASCII hex chars
+    let serial_number = unsafe { core::str::from_utf8_unchecked(&serial_buf) };
+
     let mut usb_config = UsbConfig::new(USB_VENDOR_ID, USB_PRODUCT_ID);
     usb_config.manufacturer = Some(USB_VENDOR_NAME);
     usb_config.product = Some(USB_PRODUCT_NAME);
+    usb_config.serial_number = Some(serial_number);
     usb_config.device_release = USB_RELEASE_VERSION;
     usb_config.max_power = 500;
     usb_config.max_packet_size_0 = USB_MAX_PACKET_SIZE as u8;