fix(gpio): port state not updated on DDR write

Calling `pinState()` inside a GPIO port listener returns incorrect values after changing DDR

close #47

2 files changed, 15 insertions, 0 deletions

diff --git a/src/peripherals/gpio.spec.ts b/src/peripherals/gpio.spec.ts
index 1dfaf7d..44232f4 100644
--- a/src/peripherals/gpio.spec.ts
+++ b/src/peripherals/gpio.spec.ts
@@ -92,6 +92,19 @@ describe('GPIO', () => {
       cpu.writeData(0x25, 0x01); // PORTB <- 0x01
       expect(listener).toHaveBeenCalled();
     });
+
+    it('should reflect the current port state when called inside a listener after DDR change', () => {
+      // Related issue: https://github.com/wokwi/avr8js/issues/47
+      const cpu = new CPU(new Uint16Array(1024));
+      const port = new AVRIOPort(cpu, portBConfig);
+      const listener = jest.fn(() => {
+        expect(port.pinState(0)).toBe(PinState.Low);
+      });
+      expect(port.pinState(0)).toBe(PinState.Input);
+      port.addListener(listener);
+      cpu.writeData(0x24, 0x01); // DDRB <- 0x01
+      expect(listener).toHaveBeenCalled();
+    });
   });
 
   describe('setPin', () => {
diff --git a/src/peripherals/gpio.ts b/src/peripherals/gpio.ts
index cb21669..e0861d7 100644
--- a/src/peripherals/gpio.ts
+++ b/src/peripherals/gpio.ts
@@ -110,8 +110,10 @@ export class AVRIOPort {
   constructor(private cpu: CPU, private portConfig: AVRPortConfig) {
     cpu.writeHooks[portConfig.DDR] = (value: u8) => {
       const portValue = cpu.data[portConfig.PORT];
+      cpu.data[portConfig.DDR] = value;
       this.updatePinRegister(portValue, value);
       this.writeGpio(portValue, value);
+      return true;
     };
     cpu.writeHooks[portConfig.PORT] = (value: u8) => {
       const ddrMask = cpu.data[portConfig.DDR];