Hello,
i play with beaglebone black and would like the same use of gpio as debian image,
the first step is in /boot/boot.txt
original file is here :
inside this, after :
$this->bbcode_second_pass_code('', 'gpio set 55')
you need to add :
$this->bbcode_second_pass_code('', ' fdt addr ${fdtaddr} # without this line nothing are loaded
fdt resize 0x60000 # need space for loading dtbo file
# disable HDMI
load ${devtype} ${devnum}:${bootpart} ${rdaddr} /lib/firmware/BB-NHDMI-TDA998x-00A0.dtbo
fdt apply ${rdaddr} # need after every dtbo to apply
# example load ADC cap
# load ${devtype} ${devnum}:${bootpart} ${rdaddr} /lib/firmware/BB-ADC-00A0.dtbo
# fdt apply ${rdaddr}
# example load driver for BME280 sensors connected on i2c2
# load ${devtype} ${devnum}:${bootpart} ${rdaddr} /lib/firmware/BB-I2C2-BME280.dtbo
# fdt apply ${rdaddr}
# load universal cap
load ${devtype} ${devnum}:${bootpart} ${rdaddr} /lib/firmware/univ-bbb-Exx-00A0.dtbo
fdt apply ${rdaddr}
')
with this hdmi is disabled and universal cap is loaded,
you can adapt this example to your need :
verify what available in /lib/firmware
explanation about the univ dtbo :
bbb=Classic Black, E = eMMC enabled, x = video disable, x = audio disabled
an utility called config-pin is very usefull, link,
to use it, in /boot/boot.txt, on line "setenv bootargs", at the end you need to add this :
$this->bbcode_second_pass_code('', 'bone_capemgr.uboot_capemgr_enabled=1')
another usefull utilty is show-pins, link,
after this run mkscr and reboot,
at this point config-pin and show-pins works and you can play with gpio,
but with kernel newer than 4.20, eqep don't works, and i think some other,