TS-7970 Push Button
The push switch is accessed by reading FPGA registers:
tshwctl --addr 31 --peek
With no press bit 2 will be set so it will return "addr31=0x4". If there is a press it will be cleared, so "addr31=0x0".
This pin is sampled in u-boot to detect if it should stop in u-boot and look for usb updates. If this interferes with your intended usage you can boot to u-boot and disable this by running:
env delete preboot; env set bootdelay 1; env save;
After this change u-boot will wait 1 second on every boot for the user to press ctrl+c to break into u-boot on startup.