The University of North Alabama student chapter of ACM co-sponsored the Hackable Clock V2 Project with the Department of Computer Science and Information Systems. Participants in the extracurricular project received a kit containing all of the electronic components, printed circuit board (pcb), and software tools to assemble and program their own digital alarm clock.
The digital alarm clock kit is based on the Parallax Propeller chip and the software is written in C. The clock was conceived to be "hackable". The clock's functionality can be extended using the exposed CPU pins (P8-P23) along with 3.3V and 5V power connectors designed into the pcb (for example: obtain time from GPS, use sound files for the alarm, connect the clock to wireless).
The user interface document describes how to manipulate the clock's functions. The clock functions include an alarm, two types of snooze, the date, day of week, and display brightness. All of the clock's functions are accessed using the four buttons and switch.
The software is organized into the following modules:
| Module | Description |
|---|---|
| clock.c | Main driver and user interface |
| common.h | Common definitions, shared memory variables, and pin assignments |
| ds1302.h | Definitions and pin assignments - Timekeeping IC driver |
| ds1302.c | Timekeeping IC driver |
| max7221.h | Definitions and pin assignments - LED display driver |
| max7221.c | LED display driver |
| alarm.h | Definitions and pin assignments - Alarm driver |
| alarm.c | Alarm driver |
The file clock.side is the project file and contains compiler flags, linker flags, and CPU constants.
| Schematic ID | Item | Description |
|---|---|---|
| IC1 | P8X32A | Parallax Propeller 1 (CPU) |
| IC2 | 24LC256 | 256K I2C serial EEPROM |
| IC3 | DS1302+ | Timekeeping chip w/ scratchpad RAM (RTC) |
| IC4 | MAX7221CNG | Serial interface 8-digit LED display driver |
| IC5 | SN74AHCT125N | Quad bus buffer w/ tri-state outputs (level shifter) |
| DS1 | LTC-5723HR | 4-digit LED display, red |
| U1 | LM2940-N | 5V LDO regulator, 1A |
| U2 | LM3940 | 3.3V LDO regulator, 1A |
| J1 | PJ-202A | DC power jack |
| J2 | ---- | Programming header, offset, x4 |
| J3 | ---- | 5V header, x2 |
| J4 | ---- | 3.3V header, x2 |
| J5 | ---- | CPU pin header, x8 (P8-P15) |
| J6 | ---- | CPU pin header, x8 (P16-P23) |
| S1 | EG-1218 | SPDT slide switch |
| S2 | 1825910-6 | 6MM tactile switch, thru-hole |
| S3 | 1825910-6 | 6MM tactile switch, thru-hole |
| S4 | 1825910-6 | 6MM tactile switch, thru-hole |
| S5 | 1825910-6 | 6MM tactile switch, thru-hole |
| LS1 | CMI-9605IC-0380T | Audio indicator (spkr) |
| Y1 | HC-49US | 5 MHz quartz crystal |
| Y2 | C-002RX32 | 32.768 KHz crystal |
| C1 | SVLT5R522 | 0.22 F capacitor (RTC backup) |
| C2 | FG MLCC | 0.47 uF capacitor |
| C3 | RDE MLCC | 22 uF capacitor |
| C4 | FG MLCC | 0.47 uF capacitor |
| C5 | FG MLCC | 33 uF capacitor |
| C6 | K MLCC | 0.1 uF capacitor |
| R1 | OL10535E-R52 | 10K, 1/2w, 5%, IC1 pull-up |
| R2 | OL1535E-R52 | 15K, 1/2w, 5%, ISET |
| R3 | CFR50J100R | 100, 1/2w, 5%, S1 |
| R4 | OL10535E-R52 | 10K, 1/2w, 5%, S1 pull-down |
| R5 | CFR50J100R | 100, 1/2w, 5%, S2 |
| R6 | OL10535E-R52 | 10K, 1/2w, 5%, S2 pull-down |
| R7 | CFR50J100R | 100, 1/2w, 5%, S3 |
| R8 | OL10535E-R52 | 10K, 1/2w, 5%, S3 pull-down |
| R9 | CFR50J100R | 100, 1/2w, 5%, S4 |
| R10 | OL10535E-R52 | 10K, 1/2w, 5%, S4 pull-down |
| R11 | CFR50J100R | 100, 1/2w, 5%, S5 |
| R12 | OL10535E-R52 | 10K, 1/2w, 5%, S5 pull-down |