I've created a small circuit on a couple of breadboards, with a 12 key keypad. The 7-segment LEDs consist of one 2-digit and one 4-didgit items. Each LED is connected (although not shown in breadboard diagram), to the MAX7219; D0 and D1 are connected to the 2-digit LED and D2, D3, D4 and D5 are connected to the 4-digit LED.
I've successfully checked that the OneWireKeypad works independently of the MAX7219 and 7-segment LEDs. Plus successfully checked that the MAX7219 and 7-segment LEDs work.
The problem I have is that when I link the two together via the V++ and Gnd rails, I can't get the keyboard to function. My program is fine (I'm a professional C++ Software Engineer), but I suspect that the power between the two needs some further components? Could someone please advise me how I can get the two to work as a single circuit?