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‎LICENSE

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evm-arduino
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Copyright (C) 2014, 2022 Boro Sitnikovski
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.

‎README.md

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evm-arduino
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===========
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A virtual machine for Arduino, allowing dynamic program updates.
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Based on my [implementation of CHIP-8](https://github.com/bor0/chip-8), where the gaming related instructions are removed, and instead instructions for IO pin controlling are added.
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The following instructions that are related to games (drawing, etc.) are removed:
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- `00E0`
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- `DXYN`
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- `EX9E`
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- `EXA1`
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- `FX0A`
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- `FX18`
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- `FX29`
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The following instructions that are related to IO control are added:
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- `EXA1` - sets the pin mode X to the pin (value in first register)
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- `E0A2` - does `analogRead` to the first register and stores the result in the second register
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- `E0A3` - does `analogWrite` to the first register using the value from the second register
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- `E0A4` - sleep for second register's value milliseconds
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Registers are changed from 8 bit to 16 bit.
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In order to reload a program, use the `0000` instruction to halt the VM and restart.
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Tested on ESP32 Arduino (LOLIN D32).
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References:
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- http://en.wikipedia.org/wiki/CHIP-8
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- https://github.com/bor0/chip-8
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Boro Sitnikovski

‎bin/example.asm

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6005 ; V[0] = 5 (LED_BUILTIN for ESP32)
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E2A1 ; pinMode(V[0], 2); (OUTPUT for ESP32)
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6101 ; V[1] = 1
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E0A3 ; digitalWrite(5, 1);
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62FA ; V[2] = 250
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72FA ; V[2] += 250
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72FA ; V[2] += 250
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72FA ; V[2] = 1000
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E0A4 ; delay(1000);
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6100 ; V[1] = 0
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E0A3 ; digitalWrite(5, 0);
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E0A4 ; delay(1000);
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1200 ; jump to start

‎bin/example.bin

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‎bin/example.c

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void setup() {
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pinMode(LED_BUILTIN, OUTPUT);
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}
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void loop() {
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digitalWrite(LED_BUILTIN, HIGH);
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delay(1000);
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digitalWrite(LED_BUILTIN, LOW);
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delay(1000);
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}

‎evm-arduino.ino

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/*
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This file is part of evm-arduino.
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evm-arduino is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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evm-arduino is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with evm-arduino. If not, see <http://www.gnu.org/licenses/>.
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*/
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#define WIFI_SSID "SSID"
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#define WIFI_PASSWORD "PASSWORD"
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#include <HTTPClient.h>
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#include <WiFi.h>
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#include <stdio.h>
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#include "include/vm.h"
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void setup()
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{
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Serial.begin(115200);
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delay(10);
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printf("Connecting to WiFi");
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
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while (WiFi.status() != WL_CONNECTED) {
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delay(500);
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printf(".");
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}
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printf("\nConnected to WiFi\n");
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}
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void loop()
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{
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HTTPClient client;
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struct vm VM;
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printf("Requesting (extended) CHIP-8 binary\n");
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// Sometimes downloading from GitHub causes the device to reboot. Best store on a local web server without https
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//client.begin("https://raw.githubusercontent.com/bor0/evm-arduino/main/bin/example.bin");
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client.begin("http://192.168.0.108:8080/example.bin");
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client.GET();
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printf("Initializing VM\n");
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vm_init(&VM, client.getString());
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printf("Entering VM loop\n");
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while (!VM.halt) {
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vm_cycle(&VM);
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delay(1);
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}
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printf("VM halted\n");
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}

‎include/opcodes.h

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/*
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This file is part of evm-arduino.
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evm-arduino is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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evm-arduino is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with evm-arduino. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef OPCODES_H
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#define OPCODES_H
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#include "vm.h"
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void parse_opcode(struct vm *, uint16_t);
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#endif

‎include/vm.h

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/*
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This file is part of evm-arduino.
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evm-arduino is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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evm-arduino is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with evm-arduino. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef VM_H
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#define VM_H
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#include <HTTPClient.h>
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#include <stdint.h>
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#include <stdio.h>
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struct vm {
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struct {
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/* 16 16-bit data registers named from V0 to VF. The VF register doubles as a carry flag. */
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uint16_t v[16];
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/* The address register is 16 bits wide and is used with several opcodes that involve memory operations. */
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uint16_t I;
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/* Program counter. */
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uint16_t pc;
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/* Stack pointer. */
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uint16_t sp;
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} registers;
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/* CHIP-8's memory addresses range from 200h to FFFh, making for 3,584 bytes. */
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uint8_t memory[0x0FFF];
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/* The original 1802 version allocated 48 bytes for up to 12 levels of nesting; modern implementations normally have at least 16 levels. */
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uint16_t stack[16];
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/* Halt variable. */
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uint8_t halt;
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/* Timers. */
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uint8_t delay_timer;
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};
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void vm_init(struct vm *, String);
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uint16_t calc_opcode(struct vm *);
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void vm_cycle(struct vm *);
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#endif

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