137 lines
2.9 KiB
C++
137 lines
2.9 KiB
C++
// Apple 1 Replica firmware for Arduino
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//
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// Version 1.0
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// By Ruud van Falier
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//
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// Enables serial communication between an Arduino and the Apple 1 PIA.
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// Based on Propeller source code from Briel Computers Apple 1 replica.
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// Port definitions
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#define DA A0
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#define RDA A1
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#define PB0 2
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#define PB1 3
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#define PB2 4
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#define PB3 A5
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#define PB4 A4
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#define PB5 A3
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#define PB6 A2
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#define PA0 5
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#define PA1 6
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#define PA2 7
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#define PA3 8
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#define PA4 9
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#define PA5 10
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#define PA6 11
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#define STROBE 12
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uint8_t video_data = 0;
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uint8_t video_data_pins[] = { PB0, PB1, PB2, PB3, PB4, PB5, PB6 };
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uint8_t serial_data;
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void setup()
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{
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// Setup video data pins (output from the PIA)
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pinMode(RDA, OUTPUT);
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pinMode(DA, INPUT);
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pinMode(PB0, INPUT);
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pinMode(PB1, INPUT);
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pinMode(PB2, INPUT);
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pinMode(PB3, INPUT);
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pinMode(PB4, INPUT);
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pinMode(PB5, INPUT);
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pinMode(PB6, INPUT);
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// Setup ASCII data pins (input for the PIA)
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pinMode(STROBE, OUTPUT);
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pinMode(PA0, OUTPUT);
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pinMode(PA1, OUTPUT);
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pinMode(PA2, OUTPUT);
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pinMode(PA3, OUTPUT);
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pinMode(PA4, OUTPUT);
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pinMode(PA5, OUTPUT);
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pinMode(PA6, OUTPUT);
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Serial.begin(9600);
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Serial.println("Firmware ready...");
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}
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void loop()
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{
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process_video_data();
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process_serial_data();
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}
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void process_video_data()
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{
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// Tell the PIA we are ready to receive data.
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digitalWrite(RDA, HIGH);
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delay(10);
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if (digitalRead(DA))
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{
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// Data is available.
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video_data = 0;
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// Decode the data bits to a byte.
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for (int i = 0; i < 7; i++)
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{
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if (digitalRead(video_data_pins[i]))
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{
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video_data |= (1 << i);
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}
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}
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if (video_data == 13)
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{
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// Carrage return.
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Serial.println();
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}
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else if (video_data > 31)
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{
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// Display-compatible character.
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Serial.print((char)video_data);
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}
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digitalWrite(RDA, LOW);
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delay(10);
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}
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}
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void process_serial_data()
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{
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// Wait for serial data coming in.
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if (Serial.available() > 0)
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{
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serial_data = Serial.read();
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if (serial_data == 203)
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{
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// Translate uppercase ESC to normal ESC.
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serial_data = 27;
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}
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if (serial_data >= 97 && serial_data <= 122)
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{
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// Translate lowercase characters to uppercase as the Apple 1 only supports uppercase.
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serial_data -= 32;
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}
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if (serial_data < 96)
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{
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// Encode any Apple 1 compatible character to data bits.
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digitalWrite(PA6, bitRead(serial_data, 6));
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digitalWrite(PA5, bitRead(serial_data, 5));
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digitalWrite(PA4, bitRead(serial_data, 4));
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digitalWrite(PA3, bitRead(serial_data, 3));
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digitalWrite(PA2, bitRead(serial_data, 2));
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digitalWrite(PA1, bitRead(serial_data, 1));
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digitalWrite(PA0, bitRead(serial_data, 0));
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// Pulse the STROBE bit so the PIA will process the input.
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digitalWrite(STROBE, HIGH);
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delay(20);
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digitalWrite(STROBE, LOW);
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}
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}
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} |