The holoprojector¶

Two servos aim the holo — pan for left and right, tilt for up and down — and the shared holo engine moves them the way a dome's basic holoprojectors move. For getting them connected, see Wiring the servos.

This board has exactly one holo, named holo, so its name can be left out of every command: holo wag rather than holo holo wag.

holo            # status: the light, the current motion, and both axes
holo help       # every verb and its options

Motions¶

Options, depending on the verb: -d <ms> how long a move takes, -r <pct> how far it ranges, -n <cycles> how many times, -p <ms> the period of a cycle, -t <s> how long to keep going, and -i <s-s> the interval between twitches.

holo wag -n 3 -r 60
holo scan -p 4000 -t 30
holo twitch -i 2-8

Going limp¶

The servos are not driven at boot and stay limp until something moves them. holo off, or servo_off all, releases them again; the next move picks up from wherever they were left.

Leaving a servo driven against a hard stop will cook it, so holo off is the right way to finish.

Calibrating the travel¶

Each axis has a working range in microseconds, defaulting to the range the original sketch used — 1150–1900 µs and 1300–1950 µs — inside an absolute 1000–2000 µs limit no servo is driven outside.

holo endpoints h 1150 1900     # pan: closed (full left), then open (full right)
holo endpoints v 1950 1300     # tilt reversed: closed above open turns the axis round
holo endpoints v clear         # back to the default travel

h is the horizontal axis and v the vertical. The first number is CLOSED — full left or full down — and the second is OPEN. Putting closed above open reverses the axis, which is the fix when one runs backwards.

Endpoints are saved in NVS under the pin (gpio17, gpio18), not the axis name, so they follow the wiring rather than the configuration. servo_list -o wide shows each servo's absolute and working ranges.

The individual servos¶

The servo_* commands reach the two servos one at a time, in raw microseconds rather than percentages — useful for finding the endpoints to save.

servo_list -o wide
servo_move pan 1500
servo_sweep pan -t 5
servo_config pan 1150 1900
servo_off all

servo_register re-attaches both servos; it is harmless to run, since a pin already attached is left alone.

The light¶

The holo engine also supports a light, with holo led and holo leia.