I was able to get to the bottom of the memory leak. It wasn't ArduinoJson related at all. For some reason my char* buffers weren't getting released at the end of the function. Adding free() fixed that.

I spent some time assembling the PCB backpacks for the LED bargraphs, so those are all ready. I tweaked some of the code to implement a basic bargraph. No bells and whistles yet, but it should work.

I started to replace the LEDs in the square buttons, but got sidetracked trying to figure out which resistor I should use. Ordinarily this wouldn't be so hard since I'd previously had very few, but I picked up a huge assortment of them at Radioshack on clearance.

I tried to rework my shield so I could have multiple I2C headers, but it's really fighting me. I'm just going to test the bargraphs connected directly to the Arduino.