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Writing to EEPROM using whitespace instead of spare zeros #1

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Writing to EEPROM using whitespace instead of spare zeros #1

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108 changes: 67 additions & 41 deletions multiplexed-display.ino
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Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,72 @@ void printContents() {
}
}

void programmEEPROM() {
byte digits[] = { 0x7e, 0x30, 0x6d, 0x79, 0x33, 0x5b, 0x5f, 0x70, 0x7f, 0x7b };
byte minusSign = 0x01;

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let's define a white space for the display
byte blank = 0x00;

Then the code is more readable, where we compare d2 == 0, write blank.

int progressStep = 16;
Serial.println("Programming EEPROM:");

// Go over all inputs
for (byte i = 0; i < 256; i++) {
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BUG: The comparison of the i variable with 256 is always true due to limited range of data type.

if (i % progressStep == 0) {
Serial.print((i / 256) * 100);
Serial.println("%");
}

// Non two's complement part
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How about labeling this as "Unsigned byte part"?

{
int d2 = (i / 100) % 10; // 2nd 7segment display (hundreds)
int d3 = (i / 10) % 10; // 3rd 7segment display (tenths)
writeEEPROM(i + 512 + 256, 0); // clear first 7segment display
writeEEPROM(i + 512, (d2 == 0) ? 0 : digits[d2]); // write the digit or clear if 0
writeEEPROM(i + 256, (d2 == 0 && d3 == 0) ? 0 : digits[d3]); // write the digit or clear if d3 and d2 are 0
writeEEPROM(i, digits[i % 10]); // write the digit even 0
}
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It's easier to show powers of two, when using hex notation, like this:
writeEEPROM(i + 0x300, blank); // clear first 7segment display
writeEEPROM(i + 0x200, (d2 == 0) ? blank : digits[d2]); // write the digit or clear if 0
writeEEPROM(i + 0x100, (d2 == 0 && d3 == 0) ? blank : digits[d3]); // write the digit or clear if d3 and d2 are 0
writeEEPROM(i + 0x000, digits[i % 10]); // write the digit even 0

// two's complement
{
int value = i - 128; //real value as two's complement
if (value >= 0) { // same as above
int d2 = (value / 100) % 10; // 2nd 7segment display (hundreds)
int d3 = (value / 10) % 10; // 3rd 7segment display (tenths)
writeEEPROM(value + 1024 + 512 + 256, 0); // clear first 7segment display
writeEEPROM(value + 1024 + 512, (d2 == 0) ? 0 : digits[d2]); // write the digit or clear if 0
writeEEPROM(value + 1024 + 256, (d2 == 0 && d3 == 0) ? 0 : digits[d3]); // write the digit or clear if d3 and d2 are 0
writeEEPROM(value + 1024, digits[i % 10]); // write the digit including 0
} else {
// Example
// d1 d2 d3 d4
// - 1 2 3
// - 4 2
// - 7

int d2 = (abs(value) / 100) % 10; //hundreds
int d3 = (abs(value) / 10) % 10; //tenths
int d4 = abs(value) % 10; //ones

//first 7segment display
writeEEPROM(i + 1024 + 512 + 265, d2 == 0 ? 0 : minusSign); //write a minus sign to the first 7segment display if the second 7segment display isn't clear

//second 7segment display
if (d2 == 0 && d3 == 0) { // if the minus sign is further right
writeEEPROM(i + 1024 + 512, 0); // clear second 7segment display
} else {
writeEEPROM(i + 1024 + 512, d2 == 0 ? minusSign : digits[d2]);
}

// third 7segment display
writeEEPROM(i + 1024 + 256, (d2 == 0 && d3 == 0) ? minusSign : digits[d3]); // write a minus sign if both the second and the third 7segment display are clear

// last 7segment display
writeEEPROM(i + 1024, digits[d4]); // always write the last digit (ones)

}
}
}
Serial.println("Finished");
}


void setup() {
// put your setup code here, to run once:
Expand All @@ -88,47 +154,7 @@ void setup() {
pinMode(WRITE_EN, OUTPUT);
Serial.begin(57600);


// Bit patterns for the digits 0..9
byte digits[] = { 0x7e, 0x30, 0x6d, 0x79, 0x33, 0x5b, 0x5f, 0x70, 0x7f, 0x7b };

Serial.println("Programming ones place");
for (int value = 0; value <= 255; value += 1) {
writeEEPROM(value, digits[value % 10]);
}
Serial.println("Programming tens place");
for (int value = 0; value <= 255; value += 1) {
writeEEPROM(value + 256, digits[(value / 10) % 10]);
}
Serial.println("Programming hundreds place");
for (int value = 0; value <= 255; value += 1) {
writeEEPROM(value + 512, digits[(value / 100) % 10]);
}
Serial.println("Programming sign");
for (int value = 0; value <= 255; value += 1) {
writeEEPROM(value + 768, 0);
}

Serial.println("Programming ones place (twos complement)");
for (int value = -128; value <= 127; value += 1) {
writeEEPROM((byte)value + 1024, digits[abs(value) % 10]);
}
Serial.println("Programming tens place (twos complement)");
for (int value = -128; value <= 127; value += 1) {
writeEEPROM((byte)value + 1280, digits[abs(value / 10) % 10]);
}
Serial.println("Programming hundreds place (twos complement)");
for (int value = -128; value <= 127; value += 1) {
writeEEPROM((byte)value + 1536, digits[abs(value / 100) % 10]);
}
Serial.println("Programming sign (twos complement)");
for (int value = -128; value <= 127; value += 1) {
if (value < 0) {
writeEEPROM((byte)value + 1792, 0x01);
} else {
writeEEPROM((byte)value + 1792, 0);
}
}
programmEEPROM();

// Read and print out the contents of the EERPROM
Serial.println("Reading EEPROM");
Expand Down