Device::Chip::MAX7219 - chip driver for a MAX7219


   use Device::Chip::MAX7219;
   use Future::AsyncAwait;

   my $chip = Device::Chip::MAX7219->new;
   await $chip->mount( Device::Chip::Adapter::...->new );

   await $chip->power(1);

   await $chip->intensity( 2 );
   await $chip->limit( 8 );

   await $chip->displaytest( 1 );
   await $chip->shutdown( 0 );

   sleep 3;

   await $chip->displaytest( 0 );


This Device::Chip subclass provides specific communication to a Maxim Integrated MAX7219 chip attached to a computer via an SPI adapter. As the MAX7221 chip operates virtually identically, this chip will work too.

This module drives a single MAX7219 chip. For situations involving multiple chips daisy-chained together (such as on popular LED matrix display board modules) see instead Device::Chip::MAX7219Panel.

The reader is presumed to be familiar with the general operation of this chip; the documentation here will not attempt to explain or define chip-specific concepts or features, only the use of this module to access them.


The following methods documented in an await expression return Future instances.


   await $chip->write_bcd( $digit, $val );

Writes the value at the given digit, setting it to BCD mode if not already so. $val should be a single digit number or string, or one of the special recognised characters in BCD mode of -, E, H, L, P or space. The value may optionally be followed by a decimal point ., which will be set on the display.

Switches the digit into BCD mode if not already so.


   await $chip->write_raw( $digit, $bits );

Writes the value at the given digit, setting the raw column lines to the 8-bit value given.

Switches the digit into undecoded raw mode if not already so.


   await $chip->write_hex( $digit, $val );

Similar to write_bcd, but uses a segment decoder written in code rather than on the chip itself, to turn values into sets of segments to display. This makes it capable of displaying the letters A to F, in addition to numbers, - and space.


   await $chip->set_decode( $bits );

Directly sets the decode mode of all the digits at once. This is more efficient for initialising digits into BCD or raw mode, than individual calls to write_bcd or write_raw for each digit individually.


   await $chip->intensity( $value );

Sets the intensity register. $value must be between 0 and 15, with higher values giving a more intense output.


   await $chip->limit( $columns );

Sets the scan limit register. $value must be between 1 and 8, to set between 1 and 8 digits. This should only be used to adjust for the number of LED digits or columns units physically attached to the chip; not for normal display blanking, as it affects the overall intensity.

Note that this is not directly the value written to the LIMIT register.


   await $chip->shutdown( $off );

Sets the shutdown register, entirely blanking the display and turning off all output if set to a true value, or restoring the display to its previous content if set false.

Note that this is not directly the value written to the SHUTDOWN register.


   await $chip->displaytest( $on );

Sets the display test register, overriding the output control and turning on every LED if set to a true value, or restoring normal operation if set to false.


Paul Evans <>