I'm trying to get a MAX 7219 hooked up to my Arduino Uno and some very strange things are happening.
I've gone through the process of writing my own code to drive it, then taking the playground example of an 8x8 matrix, but neither of these is actually making any change to the LED state. Because of this, I've been slowly stripping away sections of code to get back to something that works.
I've now got to the stage where I have completely removed the arduino
I've got this prototyped up on breadboard - schematic attached - and my test LED is always on from the moment power is applied. According to the datasheet, this chip should power on in a shutdown mode, with all outputs disabled, that needs to be setup via the serial interface before any LEDs will turn on. Additionally, If I don't ground the DIN/LOAD/CLK lines then the LEDs flicker annoyingly between a full bright (measured at 10mA, the set value from R1) and barely on.
I've tried adding some close decoupling by means of C1 and C2, with no difference.
Has anyone experienced this before?
Every webpage, blog and forum post espouses how simple and easy to use these chips are, but that's not my experience. So far I've tried two different chips, I've got another 8 to go, but I'm reluctant to just throw them in and see what happens, in case it's me thats breaking them.
As they were bought for not very much money via ebay from some guy in HK, is it conceivable that they could be fakes or mistreated?
Pol.