1 files changed, 149 insertions, 0 deletions
diff --git a/src/peripherals/gpio.ts b/src/peripherals/gpio.ts
new file mode 100644
index 0000000..a667967
--- /dev/null
+++ b/src/peripherals/gpio.ts
@@ -0,0 +1,149 @@
+/**
+ * AVR-8 GPIO Port implementation
+ * 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, 2020, Uri Shaked
+ */
+import { CPU } from '../cpu/cpu';
+import { u8 } from '../types';
+
+export interface AVRPortConfig {
+  // Register addresses
+  PIN: u8;
+  DDR: u8;
+  PORT: u8;
+}
+
+export type GPIOListener = (value: u8, oldValue: u8) => void;
+
+export const portAConfig: AVRPortConfig = {
+  PIN: 0x20,
+  DDR: 0x21,
+  PORT: 0x22
+};
+
+export const portBConfig: AVRPortConfig = {
+  PIN: 0x23,
+  DDR: 0x24,
+  PORT: 0x25
+};
+
+export const portCConfig: AVRPortConfig = {
+  PIN: 0x26,
+  DDR: 0x27,
+  PORT: 0x28
+};
+
+export const portDConfig: AVRPortConfig = {
+  PIN: 0x29,
+  DDR: 0x2a,
+  PORT: 0x2b
+};
+
+export const portEConfig: AVRPortConfig = {
+  PIN: 0x2c,
+  DDR: 0x2d,
+  PORT: 0x2e
+};
+
+export const portFConfig: AVRPortConfig = {
+  PIN: 0x2f,
+  DDR: 0x30,
+  PORT: 0x31
+};
+
+export const portGConfig: AVRPortConfig = {
+  PIN: 0x32,
+  DDR: 0x33,
+  PORT: 0x34
+};
+
+export const portHConfig: AVRPortConfig = {
+  PIN: 0x100,
+  DDR: 0x101,
+  PORT: 0x102
+};
+
+export const portJConfig: AVRPortConfig = {
+  PIN: 0x103,
+  DDR: 0x104,
+  PORT: 0x105
+};
+
+export const portKConfig: AVRPortConfig = {
+  PIN: 0x106,
+  DDR: 0x107,
+  PORT: 0x108
+};
+
+export const portLConfig: AVRPortConfig = {
+  PIN: 0x109,
+  DDR: 0x10a,
+  PORT: 0x10b
+};
+
+export enum PinState {
+  Low,
+  High,
+  Input,
+  InputPullUp
+}
+
+export class AVRIOPort {
+  private listeners: GPIOListener[] = [];
+
+  constructor(private cpu: CPU, private portConfig: AVRPortConfig) {
+    cpu.writeHooks[portConfig.PORT] = (value: u8, oldValue: u8) => {
+      const ddrMask = cpu.data[portConfig.DDR];
+      cpu.data[portConfig.PORT] = value;
+      value &= ddrMask;
+      cpu.data[portConfig.PIN] = (cpu.data[portConfig.PIN] & ~ddrMask) | value;
+      this.writeGpio(value, oldValue & ddrMask);
+      return true;
+    };
+    cpu.writeHooks[portConfig.PIN] = (value: u8) => {
+      // Writing to 1 PIN toggles PORT bits
+      const oldPortValue = cpu.data[portConfig.PORT];
+      const ddrMask = cpu.data[portConfig.DDR];
+      const portValue = oldPortValue ^ value;
+      cpu.data[portConfig.PORT] = portValue;
+      cpu.data[portConfig.PIN] = (cpu.data[portConfig.PIN] & ~ddrMask) | (portValue & ddrMask);
+      this.writeGpio(portValue & ddrMask, oldPortValue & ddrMask);
+      return true;
+    };
+  }
+
+  addListener(listener: GPIOListener) {
+    this.listeners.push(listener);
+  }
+
+  removeListener(listener: GPIOListener) {
+    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);
+    }
+  }
+}