HC-SR04 → live

Polls DIST:? at 5 Hz when streaming is on. Firmware replies DIST:<cm> or DIST:- if no echo. The bar maxes at 200 cm; dashes appear when out of range.

— cm
last 60 readings
// hardware HC-SR04 plugs into J6 (silk: vcc / trig / echo / gnd). The ECHO line goes through R4/R5 voltage divider (5V → 3.3V) before reaching GPIO 20. TRIG fires on GPIO 21.