p18clock is an alarm clock based on a PIC18F2550 microcontroller. The project leverages the libledmtx library to drive a LED dot matrix display.
p18clock includes the following features:
- Time and date function
- Display temperature in degrees Celsius
- 24h alarm
- Automatic cycle of display mode every few seconds
demo.webm
The clock is based on a finite state machine that is described in the following diagram. It has four push buttons: MODE, SET, UP, DOWN. MODE triggers the transition between main states. SET can be used to cycle across sub-states. UP/DOWN can be used to change the value for a setting.
B_MODE
,-----------------------------------------------------------------------------------.
v `|
+------------+ +------------+ +------------+ +-------------+ +------------+
| STATE_TIME | -----> | STATE_DATE | -----> | STATE_TEMP | -----> | STATE_ALARM | -----> | STATE_AUTO |
+------------+ B_MODE +------------+ B_MODE +------------+ B_MODE +-------------+ B_MODE +------------+
| ^ | ^ | ^ | ^
| B_SET \ | B_SET \ | B_SET \ | B_SET |
v ` v ` v ` v `
+----------+ ` +----------+ ` +---------+ ` +----------+ `
| _SETHOUR | | | _SETMDAY | | | _SETVDD | | | _SETHOUR | |
+----------+ | +----------+ | +---------+ | +----------+ |
| B_SET | | B_SET | | B_SET | | B_SET |
v | v | v | v |
+----------+ , +----------+ | +---------+ , +----------+ ,
| _SETMIN |-- | _SETMON | | | _SETOFF |-- | _SETMIN |--
+----------+ +----------+ | +---------+ +----------+
| B_SET |
v |
+----------+ ,
| _SETYEAR |--
+----------+
STATE_TIME: Display current time STATE_DATE: Display current date
STATE_TEMP: Display temperature STATE_ALARM: Display scheduled alarm
STATE_AUTO: Auto-cycle display modes above
_SETHOUR: Set current time - hour _SETMIN: Set current time - minutes
_SETMDAY: Set current date - day _SETMON: Set current date - month
_SETYEAR: Set current date - year
_SETVDD: Manually set VDD (if HLVD fails) _SETOFF: Set temperature offset, e.g. to compensate
for a specific physical location
_ALARM_SETHOUR: Set alarm time - hour _ALARM_SETMIN: Set alarm time - minutes
p18clock requires a libledmtx installation in the $HOME/.local/libledmtx/ directory:
$ git clone --depth=1 https://github.com/jalopezg-git/libledmtx/
$ cd libledmtx/
$ make
$ make INSTALL_PREFIX=$HOME/.local/libledmtx/ install
$ cd ../Afterwards, p18clock can be built as follows:
$ # Generate `p18clock.hex`; the image can be flashed into the MCU via pk2cmd
$ make P18CLOCK_LANG=EN # or `P18CLOCK_LANG=ES` to use Spanish translation
A sketch of the wiring can be found here. The display is made up from six 5x7 Kingbright TC12-11SRWA parts where row pins have been physically connected, thus resulting in a 30x7 dot matrix. For the LED dot matrix display, refer to the libledmtx hardware description.
Push buttons are wired to a 74HC148 binary encoder whose output is connected to RB<1:3>; this makes it possible to have up to 7 push buttons using few I/O pins. A change on a PORTB pin triggers a INT0 interrupt. The INT0 handler places the corresponding message in a circular buffer, that is to be dispatched from the main loop.
100 nF decoupling capacitors are placed near the Vdd lines of the microcontroller, together with two 4.7 uF "bulk" capacitors placed near the power lines on the board.
The secondary oscillator used as a RTC is a 32.768 kHz crystal. Temperature measuring is based on the well-known LM35 temperature sensor.