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.

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 <>