Cascade several 7-segment display modules

[bschymanski]

is it possible to use (cascade) multiple max7219 7-segment display modules?

[tekktrik]

Datasheet says it's doable! Check out page 13:

https://cdn-shop.adafruit.com/datasheets/MAX7219.pdf

[bschymanski]

Yes, but the library does not allow to set more then 8 digits.

[tekktrik]

Ah, got it! I wonder if it can be made configurable!

[bschymanski]

Hi,

how should i use the code now?
This does not work: "segment = bcddigits.BCDDigits(spi, cs, nDigits=16)"

code.py output:
Traceback (most recent call last):
File "code.py", line 14, in
File "adafruit_max7219/bcddigits.py", line 41, in init
File "adafruit_max7219/max7219.py", line 101, in init
File "adafruit_max7219/bcddigits.py", line 52, in init_display
File "adafruit_max7219/max7219.py", line 161, in write_cmd
OverflowError: value must fit in 1 byte(s)

[tekktrik]

@bschymanski you'll need to save this library (as specifically this pull request branch) from GitHub and place it in your board's lib folder in order to test it

[tekktrik]

You can download the repository as this ZIP file: https://github.com/tekktrik/Adafruit_CircuitPython_MAX7219/archive/refs/heads/dev/chainable-bcd-digits.zip

Take the folder labeled adafruit_max7219 in there and use it instead of the one you've been using. That way we can test this in progress branch.

[tekktrik]

Once you do that, you should be able to use it as you've done earlier with:

segment = bcddigits.BCDDigits(spi, cs, nDigits=16)

If not, I'll have to make changes!

[bschymanski]

I still get the same error:
code.py output:
Traceback (most recent call last):
File "code.py", line 15, in
File "/lib/adafruit_max7219/bcddigits.py", line 42, in init
File "/lib/adafruit_max7219/max7219.py", line 190, in init
File "/lib/adafruit_max7219/max7219.py", line 101, in init
File "/lib/adafruit_max7219/bcddigits.py", line 53, in init_display
File "/lib/adafruit_max7219/max7219.py", line 207, in write_cmd
OverflowError: value must fit in 1 byte(s)

[tekktrik]

Thanks for testing! I see the issue, I'll let you know when it's ready for another test!

[tekktrik]

Okay @bschymanski I should have fixed that error, so hopefully if you redownload the library and use it, it should be good!

https://github.com/tekktrik/Adafruit_CircuitPython_MAX7219/archive/refs/heads/dev/chainable-bcd-digits.zip

[bschymanski]

Hi,

i am so sorry, but it sill produces the same error:

code.py output:
Traceback (most recent call last):
File "code.py", line 14, in
File "/lib/adafruit_max7219/bcddigits.py", line 42, in init
File "/lib/adafruit_max7219/max7219.py", line 190, in init
File "/lib/adafruit_max7219/max7219.py", line 101, in init
File "/lib/adafruit_max7219/bcddigits.py", line 52, in init_display
File "/lib/adafruit_max7219/max7219.py", line 213, in write_cmd
OverflowError: value must fit in 1 byte(s)

Code done running.

This ist the sketch running on the raspberry pi pico:

import time
import board
import busio
import digitalio

import adafruit_framebuf

from adafruit_max7219 import bcddigits

mosi = board.GP7
clk = board.GP6
cs = digitalio.DigitalInOut(board.GP5)
spi = busio.SPI(clk, MOSI=mosi)
leds = bcddigits.BCDDigits(spi, cs, nDigits=16)

leds.brightness(0)
leds.clear_all()

place 8-digit number on display

value = 12345678

leds.show_str(0, "{:8}".format(value))
leds.show()

[tekktrik]

Thank you so, so much again for helping me test this. It seems I forgot to use a bit mask to keep the number(s) being sent fitting within a single byte. The latest code I pushed fixes this. Redownloading from the link should provide the fix.

[bschymanski]

Hi, no problem, i would like to use it afterwards...

and it kind of works... at least it does not give me an error anymore, but the output is not what i would expect, it is not really daisy chained:

This is the code:

import time
import board
import busio
import digitalio

import adafruit_framebuf

from adafruit_max7219 import bcddigits

mosi = board.GP7
clk = board.GP6
cs = digitalio.DigitalInOut(board.GP5)
spi = busio.SPI(clk, MOSI=mosi)
leds = bcddigits.BCDDigits(spi, cs, nDigits=16)


leds.brightness(0)
leds.clear_all()
# place 8-digit number on display
value = 12345678

leds.show_str(0, "11112222")
leds.show_str(8, "33334444")
leds.show()

and the output looks like this:

[tekktrik]

Progress! Let me look into what's going on here, I'm probably not doing the SPI communication correctly. Thanks again for testing!

[Jibun-no-Kage]

@bschymanski, Post the working code?