I have a central controller utilizing a K64 MCU that communicates on a UART buss to multiple devices which use KL26s and KL27s MCUs in a master-slave mode. Everything works pretty well up to about 8 or 9 devices. At that point, communications begin to break down.
I put a scope on the lines but everything appears okay. I have my EE checking my scope on Monday morning to verify. My thought is that the boards have some type of pull up on these lines and eventually it becomes to hard to pull the lines down and communication fails.
Because my system is modular in design, I can prove without a doubt that the number of devices is the culprit.
Has anyone experienced anything like this? Can you recommend a solution?