teensy 3.5 sequencer with SPI MCP23s17 and 8 spark fun rotary encoders

early test of the first panel of a step step sequencer. This uses rotary encoders from spark fun, with rub leds and push button. The GPIO port expanders are all on a single SPI bus, these are MCP23s17 chips. The test uses the onboard Teensy 3.5 SD card to hold a pattern in memory. This in the step on/off value and the note value. The memory slot is recalled and loaded to the sequencer by a button push. The midi bpm is controllable, as well as step number and direction. The sequencer test sends midi signals to Ableton Live for testing . These GPIO expanders also have the capability of using interrupts, but this was proving difficult to manipulate, and so the current setup is only using polling in the loop.