The Button System in Firmware

Four buttons drive the entire interaction. The firmware turns raw presses into mode switches, parameter edits, and config entry.

The hardware mapping

Button	GPIO	Pull	Action
MODE	33	Internal	Short: mode toggle. Long 2 s: EMERGENCY
SEL	32	Internal	Short: VOL/WPM target. Long 3 s: CONFIG
UP	35	External 10 k	Increment
DN	34	External 10 k	Decrement

Debounce

Mechanical switches bounce for 1-5 ms. The firmware samples each pin on a timer (typically every 10-20 ms) and requires a stable reading for 30-50 ms before registering a press. This kills bounce without extra hardware.

Press vs hold

The firmware tracks press duration:

• Short press (< 2 s): primary action (toggle mode, toggle target).
• Long press (≥ 2 s for MODE, ≥ 3 s for SEL): secondary action (EMERGENCY, CONFIG).
• Hold 1 s (SEL): save VOL/WPM to NVS.
• Both at boot 5 s (MODE+SEL): factory reset.

Auto-repeat

Holding UP or DN repeats the increment:

• Initial delay: 500 ms.
• Repeat rate: every 150 ms.
• Volume steps: +10 per repeat. WPM steps: +1.

During TX

The buttons are interrupt-driven: an ISR sets a flag on the rising edge, and the main loop processes it between symbols. This is what makes the mid-TX abort responsive even while the radio is keyed.

The adjustment overlay

After UP/DN changes a value, the OLED shows a bottom-bar overlay with the live value for 2.5 s, then hides it. The target (VOL or WPM) is shown in the corner of the main screen.

Saving

Adjustments apply live in RAM. To persist: hold SEL for 1 s. Without a save, a reboot restores the old NVS values. This is deliberate: a mis-click should not be permanent.

Edge cases

• Both MODE and SEL pressed at boot: factory reset path (checked in setup).
• A stuck button (held by the case): the firmware sees a permanent press; the long-press actions trigger. Check the case fit if the beacon enters CONFIG or EMERGENCY by itself.