Add-on dossier
A linkable lifecycle record for hardware expansions, app ecosystems, firmware upgrades, cases, radio parts, and post-event badge experiments.
Holding the button while powering on prints Entering Sentinel Watch Mode on the console and switches the LEDs to a separate watch routine instead of the normal animation modes.
Badge context
Bryan Smith's September 26, 2026 first-hand writeup on the Redline Cyber Security blog covering the artwork, LEDs, the non-functional RECHARGE port, finding the serial pins, the pin-12 trigger, the rick astley answer, and dumping and reflashing the ATtiny1616 over UPDI.
Repository created September 26, 2026 with the unmodified 16 KB flash and 256 B EEPROM read from the badge, SHA-256 checksums, a pinout, console and UPDI wiring, and restore instructions. Organizer-authored firmware, not a source release; no licence is declared.
Official site for the September 24-25, 2026 conference at DeVos Place, Grand Rapids. The October 1, 2026 recheck still found Get Tickets and no recap or badge mention.
Source trail
Secondary first-hand attendee source for the badge's existence at the 15th-anniversary event, the artwork, LED colours, button, coin-cell power, RECHARGE port, the challenge flow and answer, the designer's FTDI warning a week before the con, and the designer credit to Dave Schwartzberg of Hak4Kidz. It does not describe how many badges were made or how they were handed out.
Official event source for the September 24-25, 2026 dates and DeVos Place venue. It does not mention the anniversary badge and still read pre-event on October 1, 2026.
Attendee archive for the ATtiny1616 identification, signature, fuse state, USART0 and UPDI pins, the PC0 trigger, the Sentinel Watch Mode message, and the GRRE EEPROM marker, describing the badge as the GrrCON 2026 Hak4Kidz challenge badge.