[RESOLVED] MAX7219 SPI Issue

SydMan

Hi,

Thought I move my previous question in different topic and share the finding here.

So I bought a MAX7219 and was playing around with the spi-tool. Looking at Arduino code and also 7219 datasheet able to do the following

// set scan limit
spi-tool -b 0 -d 1 write 0x0B 0x0f

// set power ON
spi-tool -b 0 -d 1 write 0x0C 0x1

// decode mode
spi-tool -b 0 -d 1 write 0x09 0xFF

// test mode
spi-tool -b 0 -d 1 write 0x0F 0x1

with the test mode (0x0F) able to turn on all the LED and to turn of use 0x0 for 0x0F register.

But the funny thing is when I use the write command to write on the first row like so

spi-tool -b 0 -d 1 write 0x00 0x01

I see 2 LED turned on in Row 0 which is not right. I'm attaching diagram of which LED turn on when using the following command

spi-tool -b 0 -d 1 write 0x00 <value>

Any idea why the LED is not turn on properly ?

Tested in Arduino and all works fine. I tested with Arduino using the sample code from here https://brainy-bits.com/tutorials/how-to-control-max7219-led-matrix/

SydMan

After reading the datasheet looks like I'm using the wrong decode mode. Here are the steps in case anyone is having the same problem

Following is the wiring

Following is the test bash script



#!/bin/sh
#set power ON
spi-tool -b 0 -d 1 write 0x0C 0x1

#set scan limit
spi-tool -b 0 -d 1 write 0x0B 0x0f

#decode mode
spi-tool -b 0 -d 1 write 0x09 0x01


#Set each display in use to blank
for i in 1 2 3 4 5 6 7 8 9
do
  spi-tool -b 0 -d 1 write 0x$i 0x0  
done

for i in 1 2 3 4 5 6 7 8
do
  spi-tool -b 0 -d 1 write 0x$i 0x11
done

sleep 1

for j in 0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88 0x99 0xAA 0xBB 0xCC 0xDD 0xEE 0xFF
 do
  for i in 1 2 3 4 5 6 7 8
  do
    spi-tool -b 0 -d 1 write 0x$i $j
  done
  sleep 1
 done