Busy signal always high on Teensy 3.2?

[molecule]

I saw issue #4, and swapped pins, but the example code (all of them) is still stalling out in this loop waiting for BS to go low.

On a scope, as soon as RS and CS are written high, BS also goes high and never goes low:
Output

I get the same scope output whether I swap the pins, don't swap the pins, use SW SPI or HW SPI.

Note that a few lines above that, BS is set to "INPUT PULLUP", which enables the internal pull-up resistor.

Q1: Whose job is it to drive BS low?

Reading about SPI, I'm still not sure who is supposed to drive BS down (or even what BS maps to in the usual SPI terms of MOSI, MISO, CS, and SCK). Can you provide any insight?

Q2: What does BS, CS, RS, DC mean? How do those map to typical SPI terminology? Knowing that would help me debug.

I can see from the app note that waiting for the BS pin to be low is a prerequisite to initializing the COG hardware.

Hardware:
3.2 Teensy using latest lib code downloaded just yesterday
Arduino IDE 1.6.12
Upload setup

[jareklupinski]

Apologies! No clue how I missed this for so long... the BS pin is an Input that is pulled low by the Screen's internal hardware and sensed by the CPU. Typically it is high or floating when the Screen is busy and cannot accept commands, and is pulled Low by the screen, signaling that it is ready to accept commands, similar to https://cdn-shop.adafruit.com/product-files/4243/4243_datahseet_GDEW0213I5F_V1.1_Specification__1_.pdf (can't find exact datasheet at the moment)

BS is Busy, CS is Chip Select, RS is Reset and DC is Data/Command, some of these pins are outside of normal SPI terminology and specific to the screen :)