Report UART status as events; addl UART events

demo/emulator-run.ts

@@ -14,9 +14,9 @@ loadHex(hex, mcu.flash, 0x10000000);
 const gdbServer = new GDBTCPServer(mcu, 3333);
 console.log(`RP2040 GDB Server ready! Listening on port ${gdbServer.port}`);
 
-mcu.uart[0].onByte = (value) => {
+mcu.uart[0].on('byteSent', (value) => {
   process.stdout.write(new Uint8Array([value]));
-};
+});
 
 mcu.core.PC = 0x10000000;
 mcu.execute();

package.json

@@ -65,5 +65,8 @@
     "**/*.js": [
       "prettier --write"
     ]
+  },
+  "dependencies": {
+    "eventemitter3": "^5.0.1"
   }
 }

src/peripherals/peripheral.ts

@@ -1,3 +1,4 @@
+import EventEmitter from 'eventemitter3';
 import { RP2040 } from '../rp2040';
 
 const ATOMIC_NORMAL = 0;
@@ -25,10 +26,15 @@ export interface Peripheral {
   writeUint32Atomic(offset: number, value: number, atomicType: number): void;
 }
 
-export class BasePeripheral implements Peripheral {
+// eslint-disable-next-line @typescript-eslint/ban-types -- EventEmitter3 defines the allowed types as `object`, so copy that here
+export class BasePeripheral<E extends object = Record<string, unknown>>
+  extends EventEmitter<E>
+  implements Peripheral {
   protected rawWriteValue = 0;
 
-  constructor(protected rp2040: RP2040, readonly name: string) {}
+  constructor(protected rp2040: RP2040, readonly name: string) {
+    super();
+  }
 
   readUint32(offset: number) {
     this.warn(`Unimplemented peripheral read from ${offset.toString(16)}`);

src/peripherals/uart.ts

@@ -27,13 +27,25 @@ const UARTEN = 1 << 0;
 // Interrupt bits
 const UARTRXINTR = 1 << 4;
 
-export class RPUART extends BasePeripheral implements Peripheral {
+type UartEvents = {
+  /** the MCU has written a byte to the UART */
+  byteSent: (value: number) => void;
+  /** readFhe MCU's read FIFO is full, and any further bytes fed to the UART will be dropped */
+  readFifoFull: () => void;
+  /** the MCU's read FIFO is empty */
+  readFifoEmpty: () => void;
+  /** the MCU has read a byte from the UART */
+  byteConsumed: () => void;
+};
+
+export class RPUART extends BasePeripheral<UartEvents> implements Peripheral {
   private ctrlRegister = RXE | TXE;
   private lineCtrlRegister = 0;
   private rxFIFO = new FIFO(32);
   private interruptMask = 0;
   private interruptStatus = 0;
 
+  /** @deprecated prefer `on("byteSent", callback)` */
   public onByte?: (value: number) => void;
 
   constructor(rp2040: RP2040, name: string, readonly irq: number) {
@@ -95,6 +107,13 @@ export class RPUART extends BasePeripheral implements Peripheral {
           this.interruptStatus |= UARTRXINTR;
           this.checkInterrupts();
         }
+        if (this.rxFIFO.empty) {
+          this.emit('readFifoEmpty');
+        }
+        if (this.rxFIFO.full) {
+          this.emit('readFifoFull');
+        }
+        this.emit('byteConsumed');
         return value;
       }
       case UARTFR:
@@ -115,9 +134,12 @@ export class RPUART extends BasePeripheral implements Peripheral {
 
   writeUint32(offset: number, value: number) {
     switch (offset) {
-      case UARTDR:
-        this.onByte?.(value & 0xff);
+      case UARTDR: {
+        const byte = value & 0xff;
+        this.onByte?.(byte);
+        this.emit('byteSent', byte);
         break;
+      }
 
       case UARTLCR_H:
         this.lineCtrlRegister = value;