This is a micropython library for MAX7219 IC. Note that some boards using this have the numbers wired in reverse, this library follows the order of the pinout as defined in the datasheet of the MAX7219, however functions are provided to reverse the order if needed.

I have tested it with a PICO, running micropython version 1.20.0.

Requires a minimum of three spare GPIO lines to run SPI.

Manual for Display:

This is for setting up the max7219 IC for use, it takes up to 4 parameters The 1st is the SPI connection, the 2ed is the cable select pin. The 3ed is optional and is the brightness/intensity, this can be 0-15, this defaults to 3, set this with intensity=15 The 4th is optional and is the number of digits in the display, defaults to 7 (digits 0-7), set this with scan_limit=15, this value should be 8 * [number of daisy chained MAX7219s] - 1

Manual for write_digits:

This takes 2 parameters, the 1st is the value to set and the optional second is the last digit's position you want to update, counting from 0. This defaults to 7, the last digit using on the pin out of the MAX7219. This function accepts the 1st parameter as a string or number

Manual for write_digits_from_list:

This function is exclusively for setting numbers as fast as possible. This takes 2 parameters, the 1st is the value to set and the optional second is the last digit you want to update, counting from 0. This defaults to 7, the last digit using on the pin out of the MAX7219. This function accepts the 1st parameter as a list. Using 0-9 in the array will set the digit to the number given. Using a 10-19 will apply a decimal point to the second digit (10='0.')

Manual for write_digits_reverse:

This takes 2 parameters, the 1st is the value to set, this can be a number, string, or list. The second is the optional start position (defaults to 0) This has a performance hit when the data type is not a list! See source code for more info.

Manual for write_all_digits:

This takes 2 parameters, the 1st is the value to set (number, string, or list) and the optional second is a boolean indicting if the order needs to be reversed, defaults to False. This will pad values to the left with 0 for a list or space otherwise. For example with a list of [13,1,4] would become [0,0,0,0,0,13,1,4] and a string 12345 would become `` 12345``, this is decimal point safe.

Manual for write_digit_segments:

This takes 2 parameters, the 1st is a list of segments (['A','b','.']) this list can be empty to blank the digit. The second parameter is the digit to be set. This is the function you would use for a LED matrix display panel. See led_test.py for example code.

Manual for round_to_fit_length:

This takes 2 parameters, the 1st is a number. The second optional parameter is the max length of the number (defaults to 8) This will round or truncate the number to make it fit in the length given. This value is returned as a int or float number.

THIS DOES NOT SET ANYTHING TO THE MAX7219

Examples:

• round_to_fit_length(3.14159265359, 6) = 3.14159
• round_to_fit_length(3.14159265359, 5) = 3.1416
• round_to_fit_length(42069, 3) = 420
• round_to_fit_length(42069, 12) = 42069
• round_to_fit_length(21.457264, 2) = 21
• round_to_fit_length(21.457264, 4) = 21.46
• round_to_fit_length(21.99, 2) = 22

In Theory using a last digit value of 15 would start at the end of the second MAX7219 connected to the DOUT pin of the 1st MAX7219

I have not tested using daisy chained MAX7219, but I think all you will need to do is set the scan_limit higher max7219.Display(spi, ss, scan_limit=15) or max7219.set_scan_limit(15) then it should just work... I hope...

Example of use (see debug_max7219.py for more):

# Connections:
# SCK (CLK) -> GP2 (4)
# MOSI (DIN) -> GP3 (5)
# SS (CS) -> GP5 (7)

from machine import Pin, SPI
from time import sleep
import max7219

spi = SPI(0, baudrate=10000000, polarity=1, phase=0, sck=Pin(2), mosi=Pin(3))
cs = Pin(5, Pin.OUT)

# Configure display
# Brightness of display are 0 - 15, default is 3
# 0 is dim and 15 is bright
display = max7219.Display(spi, cs)
#display = max7219.Display(spi, cs, intensity=0)

# Change brightness
#display.set_intensity(2)

# Display 12345678
display.write_digits(12345678)
sleep(3)

# Display 12.3456.78
display.write_digits('12.3456.78')
sleep(3)

# Alter first 4 digits, digits 0 - 3
display.write_digits(3.141,3)
sleep(3)

# Alter last 4 digits, digits 4 - 7
display.write_digits(5926,7)
sleep(3)

# Clear the display, notice this is write_all_digits, not write_digits
display.write_all_digits('')
sleep(3)

# Alter digits 2 through 6
display.write_digits('3456',5)
sleep(3)

# Display Pi without using string processing
display.write_digits_from_list([13,1,4,5,9,2,6,5])
sleep(3)

# Turn on all segments of digit 0
display.write_digit_segments(['A','b','C','D','E','F','g','.'],0)
sleep(3)

# Turn off all segments of digit 0
display.write_digit_segments([],0)