feat(usart): add onLineTransmit callback

2 files changed, 56 insertions, 0 deletions

diff --git a/src/usart.spec.ts b/src/usart.spec.ts
index f0dacc4..dadfc78 100644
--- a/src/usart.spec.ts
+++ b/src/usart.spec.ts
@@ -113,4 +113,47 @@ describe('USART', () => {
       expect(cpu.data[0xc0]).toEqual(0x40 | 0x20); // UCSR0A: TXC | UDRE
     });
   });
+
+  describe('onLineTransmit', () => {
+    it('should call onLineTransmit with the current line buffer after every newline', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+      usart.onLineTransmit = jest.fn();
+      cpu.writeData(0xc1, 0x8); // UCSR0B <- TXEN
+      cpu.writeData(0xc6, 0x48); // 'H'
+      cpu.writeData(0xc6, 0x65); // 'e'
+      cpu.writeData(0xc6, 0x6c); // 'l'
+      cpu.writeData(0xc6, 0x6c); // 'l'
+      cpu.writeData(0xc6, 0x6f); // 'o'
+      cpu.writeData(0xc6, 0xa); // '\n'
+      expect(usart.onLineTransmit).toHaveBeenCalledWith('Hello');
+    });
+
+    it('should not call onLineTransmit if no newline was received', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+      usart.onLineTransmit = jest.fn();
+      cpu.writeData(0xc1, 0x8); // UCSR0B <- TXEN
+      cpu.writeData(0xc6, 0x48); // 'H'
+      cpu.writeData(0xc6, 0x69); // 'i'
+      expect(usart.onLineTransmit).not.toHaveBeenCalled();
+    });
+
+    it('should clear the line buffer after each call to onLineTransmit', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const usart = new AVRUSART(cpu, usart0Config, FREQ_16MHZ);
+      usart.onLineTransmit = jest.fn();
+      cpu.writeData(0xc1, 0x8); // UCSR0B <- TXEN
+      cpu.writeData(0xc6, 0x48); // 'H'
+      cpu.writeData(0xc6, 0x69); // 'i'
+      cpu.writeData(0xc6, 0xa); // '\n'
+      cpu.writeData(0xc6, 0x74); // 't'
+      cpu.writeData(0xc6, 0x68); // 'h'
+      cpu.writeData(0xc6, 0x65); // 'e'
+      cpu.writeData(0xc6, 0x72); // 'r'
+      cpu.writeData(0xc6, 0x65); // 'e'
+      cpu.writeData(0xc6, 0xa); // '\n'
+      expect(usart.onLineTransmit).toHaveBeenCalledWith('there');
+    });
+  });
 });
diff --git a/src/usart.ts b/src/usart.ts
index da5cee0..8d5691c 100644
--- a/src/usart.ts
+++ b/src/usart.ts
@@ -28,6 +28,7 @@ export const usart0Config: USARTConfig = {
 };
 
 export type USARTTransmitCallback = (value: u8) => void;
+export type USARTLineTransmitCallback = (value: string) => void;
 
 // Register bits
 const UCSRA_RXC = 0x80; // USART Receive Complete
@@ -57,6 +58,9 @@ const UCSRC_UCPOL = 0x1; // Clock Polarity
 
 export class AVRUSART {
   public onByteTransmit: USARTTransmitCallback | null = null;
+  public onLineTransmit: USARTLineTransmitCallback | null = null;
+
+  private lineBuffer: string = '';
 
   constructor(private cpu: CPU, private config: USARTConfig, private freqMHz: number) {
     this.cpu.writeHooks[config.UCSRA] = (value) => {
@@ -73,6 +77,15 @@ export class AVRUSART {
       if (this.onByteTransmit) {
         this.onByteTransmit(value);
       }
+      if (this.onLineTransmit) {
+        const ch = String.fromCharCode(value);
+        if (ch === '\n') {
+          this.onLineTransmit(this.lineBuffer);
+          this.lineBuffer = '';
+        } else {
+          this.lineBuffer += ch;
+        }
+      }
       this.cpu.data[config.UCSRA] |= UCSRA_UDRE | UCSRA_TXC;
     };
   }