Nuts and Volts - September 2016

Escape rooms are all about timing: You’re allotted a specific amount of time (typically, an hour) to solve the puzzles and escape. Most escape room businesses use a computer for overall game timing, but what if we want to create something small and stand-alone; something we could play at a party?

Over the past few issues, we have explored all the elements to create such a prop. So, this time, we’ll knit them together to create a timed game piece that can be reconfigured from its own interface.

The Display’s the Thing

I’m using the same circuit from the July column, with the addition of another display module from Adafruit. The great thing about I2C is pin sharing; we can connect the second display right to the first (Figure 1). The second display has four seven-segment digits and includes a colon in the middle which makes it perfect for displaying time.

Yes, we can display time on the 14-segment display, but it’s not ideal without the colon. Humans are very visual and prefer little clues like a colon which is used when formatting standard time.

Before we get to the displays, let’s get to the heart of them. Both displays use the Holtek HT16K33. This chip will control up to eight digits with up to 16 segments each.

It also has the ability to scan keys, but that feature is not made available in the Adafruit displays, so we’ll skip it.

The interface is through I2C and is darn easy. The start()

method for the base object allows us to specify the I2C pins and the device address (%000...%111). The device address is combined with the HT16K33 slave ID (%1110_000_0) so that we target the correct display when more than one is on the same buss. If we run an I2C buss scanner (included in article downloads), we’ll see the independent addresses of the displays (Figure 2). There’s only a few control registers that we have to be concerned with; most of our work will be writing segment data to the display. On power-up, the HT16K33 oscillator is stopped and the display is blank. The system setup register ($2x) uses BIT0 to enable the oscillator. If we write $21 to the display, the oscillator will start running. The display control register ($8x) allows us to set the display on or off, as well as control the blinking. Blinking uses two bits which gives us none, 2 Hz, 1 Hz, or 0.5 Hz blink rates. The object keeps a copy of this byte so that one element can be changed without losing the other. We can choose between the set_display(), display_on(), and set_blink() methods to affect the display control register:

Game Time

I'm writing from the road again. This trip has me in my old stomping grounds of the Dallas-Fort Worth Metroplex. After driving a colleague to the airport, I popped into one of my favorite places in the area: Tanner Electronics. I'll need parts while I'm here, and it's great to have a source run by such lovely people. After that stop, I continued up I35 to Lewisville where I visited my friends at Escape Rooms HQ. They've only been open a few months and are booked solid — so much so that they're opening a second location. ERHQ uses Propellers (coded by yours truly) in several props and puzzles, so I'm very happy that things are going well. Their timing for creating a well-executed escape room seems to have been spot on.