Last week I built an Apple I Replica from a Briel Computers kit. While I loved the completed machine, I suffered a bit from the fact that backspace doesn’t work (you have to type the assembly *exactly* correct), and of course it loses the RAM contents when shut down.
I wanted to make an interface to the PC so I could use a modern editor and simply copy-paste to the Apple I. As a quick and dirty solution to the problem, I used an Arduino, wired it to the ASCII keyboard port of the Apple I and wrote a small sketch that listens on the serial port and sets the data pins accordingly.
Photos on Flickr.
Here’s the Arduino sketch, real simple:
/*
ASCII keyboard
Lionel Lemarie
2010-02
Listens on the serial port for characters from a PC.
Outputs the codes like an ASCII keyboard.
Compatible with Apple I Replica.
*/
// The order of the pins is chosen for minimal wire crossing
// when connected to an ASCII keyboard socket.
int ASCII0 = 7;
int ASCII1 = 8;
int ASCII2 = 3;
int ASCII3 = 5;
int ASCII4 = 4;
int ASCII5 = 6;
int ASCII6 = 2;
int STROBE = 10;
int NRESET = 9; //reset active low
// LED will blink when a character is emitted
int LED = 13;
unsigned long previousMillis = 0;
unsigned long interval = 200;
void setup()
{
analogReference(EXTERNAL); // Is this needed?
// Initialize the digital pins as output
pinMode(ASCII0, OUTPUT);
pinMode(ASCII1, OUTPUT);
pinMode(ASCII2, OUTPUT);
pinMode(ASCII3, OUTPUT);
pinMode(ASCII4, OUTPUT);
pinMode(ASCII5, OUTPUT);
pinMode(ASCII6, OUTPUT);
pinMode(STROBE, OUTPUT);
pinMode(NRESET, OUTPUT);
pinMode(LED, OUTPUT);
digitalWrite(STROBE, LOW); // set the STROBE pin to inactive
digitalWrite(NRESET, HIGH); // set the RESET pin to inactive
Serial.begin(9600);
}
void loop()
{
unsigned long currentMillis = millis();
if (Serial.available() > 0)
{
int iInput = Serial.read();
iInput &= 127;
if (iInput)
{
if (iInput>='a' && iInput<='z')
iInput = iInput - 'a' + 'A';
int D6 = LOW;
int D5 = LOW;
int D4 = LOW;
int D3 = LOW;
int D2 = LOW;
int D1 = LOW;
int D0 = LOW;
if ( iInput & 64 ) D6 = HIGH;
if ( iInput & 32 ) D5 = HIGH;
if ( iInput & 16 ) D4 = HIGH;
if ( iInput & 8 ) D3 = HIGH;
if ( iInput & 4 ) D2 = HIGH;
if ( iInput & 2 ) D1 = HIGH;
if ( iInput & 1 ) D0 = HIGH;
digitalWrite(LED, HIGH);
previousMillis = currentMillis;
// Output an A (100 0001)
digitalWrite(ASCII6, D6);
digitalWrite(ASCII5, D5);
digitalWrite(ASCII4, D4);
digitalWrite(ASCII3, D3);
digitalWrite(ASCII2, D2);
digitalWrite(ASCII1, D1);
digitalWrite(ASCII0, D0);
digitalWrite(STROBE, HIGH);
delay(40); // strobe for 40ms
digitalWrite(STROBE, LOW);
}
}
if ( (previousMillis>0) && (currentMillis-previousMillis>interval) )
{
digitalWrite(LED, LOW);
previousMillis = 0;
}
}
Live greetings from Breakpoint!
LeDimmer is a small Windows application (<200KB) that sits in the system tray and simply dims the screen around the foreground window. The numerous advantages include being able to focus on the task at hand, finding the window in focus at first glance even on multi-monitors, and it even looks nice. General Windows usage is not changed at all: click or alt-tab into a dimmed window and it brightens into focus.
This is a little physics game that I presented at Breakpoint 2007 at Easter. It’s a 96KB executable for Windows.