At each jail glyph, we install a device consisting of
- an ESP8266 module
- a beeper
- a 4x20 text LCD
- a small lipo battery
This device is not intended to be interactive in any way; turn it on and let it do its thing.
The device joins CMU's wireless network, performs SNTP to get an accurate clock, and connects to a MQTT server managed by the KGB to receive updates about the game for display, namely:
- game configuration (setup duration, N rounds M seconds long)
- game start time
- team scores / flag capture counts
- game over
The devices heartbeat into their own MQTT topics as well, so judges can know they are still running and, as a test, include in the heartbeat message which AP they're associated with.
The first instantiation, just as a baseline:
| 1 | NodeMCU board (ESP8266+USB serial) | 4.00 |
| 1 | 2.5Ah USB power stick | 5.50 |
| 1 | 4x20 LCD display | 4.50 |
| 1 | Buzzer | 0.20 |
| 1 | Small breadboard | 0.80 |
| Jumper wire, double-stick tape, twist-ties | 0.50 | |
| TOTAL | 15.50 |
We have found it necessary, on occasion, to add a 100-ohm resistor between power and ground to keep the USB power sticks from automagically turning off due to low draw. It's not great, but it works.
| GPIO | Purpose |
| 0 | FLASH (button) |
| 1 | Reserved for Lua console TX via USB |
| 2 | Free for good use |
| 3 | Reserved for Lua console RX via USB |
| 4 | I2C SDA for LCD-driving I/O expander |
| 5 | I2C SCL for LCD-driving I/O expander |
| 9 | Free for good use |
| 10 | Free for good use |
| 12 | free for good use |
| 13 | free for good use |
| 14 | beeper active-low |
| 15 | free for good use |
| 16 | ESP8266 WAKE; free for good use |
- ADC0 is also free at the moment.
- I2C is, of course, a multi-tap (and multi-master...) bus.