3 files changed, 69 insertions, 4 deletions

diff --git a/src/gpio.spec.ts b/src/gpio.spec.ts
index 03ebb84..e0ab7a1 100644
--- a/src/gpio.spec.ts
+++ b/src/gpio.spec.ts
@@ -1,5 +1,5 @@
 import { CPU } from './cpu';
-import { AVRIOPort, portBConfig } from './gpio';
+import { AVRIOPort, portBConfig, PinState } from './gpio';
 
 describe('GPIO', () => {
   it('should invoke the listeners when the port is written to', () => {
@@ -37,4 +37,36 @@ describe('GPIO', () => {
       expect(listener).not.toHaveBeenCalled();
     });
   });
+
+  describe('pinState', () => {
+    it('should return PinState.High when the pin set to output and HIGH', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const port = new AVRIOPort(cpu, portBConfig);
+      cpu.writeData(0x24, 0x1); // DDRB <- 0x1
+      cpu.writeData(0x25, 0x1); // PORTB <- 0x1
+      expect(port.pinState(0)).toEqual(PinState.High);
+    });
+
+    it('should return PinState.Low when the pin set to output and LOW', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const port = new AVRIOPort(cpu, portBConfig);
+      cpu.writeData(0x24, 0x8); // DDRB <- 0x8
+      cpu.writeData(0x25, 0xf7); // PORTB <- 0xF7 (~8)
+      expect(port.pinState(3)).toEqual(PinState.Low);
+    });
+
+    it('should return PinState.Input by default (reset state)', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const port = new AVRIOPort(cpu, portBConfig);
+      expect(port.pinState(1)).toEqual(PinState.Input);
+    });
+
+    it('should return PinState.InputPullUp when the pin is set to input with pullup', () => {
+      const cpu = new CPU(new Uint16Array(1024));
+      const port = new AVRIOPort(cpu, portBConfig);
+      cpu.writeData(0x24, 0); // DDRB <- 0
+      cpu.writeData(0x25, 0x2); // PORTB <- 0x2
+      expect(port.pinState(1)).toEqual(PinState.InputPullUp);
+    });
+  });
 });
diff --git a/src/gpio.ts b/src/gpio.ts
index d39a918..293c559 100644
--- a/src/gpio.ts
+++ b/src/gpio.ts
@@ -3,7 +3,7 @@
  * Part of AVR8js
  * Reference: http://ww1.microchip.com/downloads/en/DeviceDoc/ATmega48A-PA-88A-PA-168A-PA-328-P-DS-DS40002061A.pdf
  *
- * Copyright (C) 2019, Uri Shaked
+ * Copyright (C) 2019, 2020, Uri Shaked
  */
 import { CPU } from './cpu';
 import { u8 } from './types';
@@ -83,10 +83,17 @@ export const portLConfig: AVRPortConfig = {
   PORT: 0x10b
 };
 
+export enum PinState {
+  Low,
+  High,
+  Input,
+  InputPullUp
+}
+
 export class AVRIOPort {
   private listeners: GPIOListener[] = [];
 
-  constructor(cpu: CPU, portConfig: AVRPortConfig) {
+  constructor(private cpu: CPU, private portConfig: AVRPortConfig) {
     cpu.writeHooks[portConfig.PORT] = (value: u8, oldValue: u8) => {
       const ddrMask = cpu.data[portConfig.DDR];
       value &= ddrMask;
@@ -114,6 +121,25 @@ export class AVRIOPort {
     this.listeners = this.listeners.filter((l) => l !== listener);
   }
 
+  /**
+   * Get the state of a given GPIO pin
+   *
+   * @param index Pin index to return from 0 to 7
+   * @returns PinState.Low or PinState.High if the pin is set to output, PinState.Input if the pin is set
+   *   to input, and PinState.InputPullUp if the pin is set to input and the internal pull-up resistor has
+   *   been enabled.
+   */
+  pinState(index: number) {
+    const ddr = this.cpu.data[this.portConfig.DDR];
+    const port = this.cpu.data[this.portConfig.PORT];
+    const bitMask = 1 << index;
+    if (ddr & bitMask) {
+      return port & bitMask ? PinState.High : PinState.Low;
+    } else {
+      return port & bitMask ? PinState.InputPullUp : PinState.Input;
+    }
+  }
+
   private writeGpio(value: u8, oldValue: u8) {
     for (const listener of this.listeners) {
       listener(value, oldValue);
diff --git a/src/index.ts b/src/index.ts
index bdf7621..ead8081 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,3 +1,9 @@
+/**
+ * AVR8js
+ *
+ * Copyright (C) 2019, 2020, Uri Shaked
+ */
+
 export { CPU, ICPU, CPUMemoryHook, CPUMemoryHooks } from './cpu';
 export { avrInstruction } from './instruction';
 export { avrInterrupt } from './interrupt';
@@ -16,6 +22,7 @@ export {
   portHConfig,
   portJConfig,
   portKConfig,
-  portLConfig
+  portLConfig,
+  PinState
 } from './gpio';
 export { AVRUSART, usart0Config } from './usart';