When Roberto Tyley saw his son’s birthday party exterminated, it ultimately led him to invest time in an amazing Doctor Who-themed treasure hunt, as David Crookes explains.

Last year, many Doctor Who fans embarked on a virtual treasure hunt in a bid to find Jodie Whittaker’s Time Lord. Fast forward to 2022, and maker Roberto Tyley has created a physical hunt – one in which his son, Alexander, was tasked with fixing the TARDIS by finding and entering a series of passphrases with the help of his friends.

The idea evolved over time, sparked by the cancellation of Roberto’s son’s seventh birthday party in 2020. The following year’s bash was held outdoors as a treasure hunt in the local park and the children had to find clues to unlock a LEGO combination safe. “My son loved it so much, he wanted another treasure hunt – but how was I going to top last year’s party?,” Roberto says.

His plan was to hide two screen-based devices in different areas of the park, each taking it in turns to generate passphrases which could then be entered into a treasure safe. By ensuring the devices couldn’t be moved once they were found, the children would need to split into three teams – two by the devices and one by the safe. They’d wait for the passphrases to appear, and co-ordinate the unlocking over their walkie-talkies.

Reach for the stars

The passphrase devices were made using a couple of Pico-Clock-Green LED-digit electronic clocks fitted with Raspberry Pi Pico boards and programmed so that they would display a series of words. Roberto ditched the safe, however, in favour of a TARDIS built out of LEGO, which he designed using Bricklink’s Studio 2.0. 

“The idea was that the children would find the TARDIS in distress,” Roberto explains. “Its memory is scrambled and only recoverable with the right sequence of passphrases! As the children enter passphrases the windows would gradually light up with a steady light, and finally the TARDIS would be fixed.”

To enable the inputting of passphrases, the TARDIS was fitted with a Keybow 2040 – Pimoroni’s 16-key mini mechanical keyboard, chosen because it incorporates the RP2040 chip from Raspberry Pi. It allowed Roberto to code the device to figure if the correct passphrase was being entered. He then assigned eight of the keys to a set of adjectives and the other eight to nouns. “I thought typing in passphrases letter-by-letter could get a bit laborious, so I made each one a simple combination of two words,” he says.

Playing for time

The passphrases had a distinct Doctor Who theme. “My son was intrigued by the ‘Bad Wolf’ mystery in season one – so I made all the passphrases like that: “Bad Wolf”, “Good Duck”, “Fire Goat” and so on, giving 64 possible phrases,” Roberto adds. But, in order for the TARDIS to know which passphrases were being generated at any given time, the devices needed a trio of precision Real Time Clocks (RTC). 

“Each passphrase is only valid for ten seconds, so the devices need to have an accurate RTC to ensure they’re synchronised in their choice of passphrase,” Roberto says. “To make it even harder, the passphrases needed to be shouted out over the walkie talkies as quickly as possible and the children had to enter six correct passphrases in a row to ‘fix’ the TARDIS.”

As you can imagine, the birthday went down a treat, but it was certainly a learning curve for Roberto who hadn’t even heard about Raspberry Pi Pico before he planned the project. He was still putting the finishing touches to the code as the party got started. “But it was worth all the time and effort,” he says. “My son and his friends totally loved the game and I’d definitely do it all again.

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