Arduino MAX7219 7-segment display library by Frost Sheridan

This is a simple library for displaying numbers on a 7-segment display that is being driven with a MAX7219 IC.

Using the library

Declaring the MAX7219 object

MAX7219 object_name(data_pin,clock_pin,latch_pin,num_digits);

• object_name is the name of the object
• data_pin is the Arduino pin that the MAX7219 data/DIN pin is connected to
• clock_pin is the Arduino pin that the MAX7219 clock pin is connected to
• latch_pin is the Arduino pin that the MAX7219 latch/CS pin is connected to
• num_digits is the number of digits on the display (1 to 8)

Functions available

void MAX7219::init() - Sets up the display. Must be called before the display is used for it to work correctly.

void MAX7219::writeRegister(uint8_t address,uint8_t data) - Writes a byte directly to one of the control registers of the MAX7219.

void MAX7219::setBrightness(uint8_t brightness) - Sets the brightness of the entire display (0 is lowest, 15 is highest).

void MAX7219::updateDisplay() - Sends the contents of VRAM to the display. Must be called to make any changes made to the contents of the display visible.

void MAX7219::fillDisplay(uint8_t data) - Sets all of the digits of the display to a specific value. (Hint: to clear the display, use fillDisplay(MAX_CHAR_BLANK))

void MAX7219::writeDigitRaw(uint8_t digit,uint8_t data) - Sets the contents of a single digit as a raw 'bitmap' of the segments.

void MAX7219::writeDigitNumber(uint8_t digit,uint8_t num) - Displays a single decimal/hexidecimal digit (num can be between 0-15).

void MAX7219::setDecimalPoint(uint8_t digit) - Turns on the decimal point of a specific digit.

uint8_t MAX7219::readDigit(uint8_t digit) - Returns the contents of a specific digit as a raw 'bitmap' of the segments.

void MAX7219::writeLong(unsigned long num,uint8_t padding_char) - Writes an integer, long, or other non-float number to the display. If the number has less than 8 digits, the unused digits to the left of the number are filled with padding_char.

void MAX7219::writeFloat(float num,uint8_t padding_char,uint8_t decimal_places) - Writes a float to the display. If the number has less than 8 digits, the unused digits to the left of the number are filled with padding_char. decimal_places is the number of digits to display to the right of the decimal point.

Constants available

Characters (use with writeDigitRaw function)

MAX_CHAR_DASH - Shows a dash - character

MAX_CHAR_UNDERSCORE - Shows an underscore _ character

MAX_CHAR_BLANK - Blanks the digit it's written to

MAX_CHAR_DECIMALPOINT - Turns on only the decimal point of the digit it's written to

Internal registers (use with writeRegister function)

MAX_REG_DIGIT - The address of the place in the MAX7219's memory to start writing digit display data to.

MAX_REG_DECODE - The address of the decode mode byte in the MAX7219's memory.

MAX_REG_BRIGHTNESS - The address of the brightness value byte in the MAX7219's memory.

MAX_REG_SCANLIMIT - The address of the number of digits - 1 in the MAX7219's memory.

MAX_REG_ENABLED - The address of the shutdown bit in the MAX7219's memory. The display is completely blanked when this is set to 0.

MAX_REG_LAMPTEST - The address of the display test bit in the MAX7219's memory. Every segment of the display is turned on when this is set to 1.

How the segments map to bits

When using the writeDigitRaw function, you write a byte to the display to turn on/off the individual segments of a digit. Each bit in that byte controls one of the digit's 8 segments: