Fish Light
Software
The software was written using Atmel Studio 6, which features GCC compiler. The device was given four keys: M , C, U and D, for providing of the input to the program. The program assumes three modes of operation:
- Automatic Mode
- Manual Mode
- Battery Mode
In the automatic mode, the color changes according to the predefined scale that was just explained. In addition to that, the manual mode allows the user to manually tune the color. Finally, since the microcontroller always needs some power in order to maintain counting of the time, the battery mode is used to ensure that the device does not restart in case of suddenly unplugging it from the mains. Although it will switch the lights off, it will still maintain counting the time.
| Key | Function | Availability |
|---|---|---|
| M | mode switch | auto/manual |
| C | selects the RGB and lamp | manual |
| U | increases the value of selected channel | manual |
| D | decreases the value of selected channel | manual |
Implementation on Atmega88
The first and most important source of information regarding the microcontoller is the datasheet [4]. I have chosen ATmega88 for the application. It is a basic project, which does not use all of the available peripherals. Most importantly, however, it possesses enough PWM channels that are required for the system to work. the following table summarises the I/O pin features that are used.
| I/O | Pin | Feature | Task |
|---|---|---|---|
PCINT0 |
PB0(14) |
pin-controlled interrupt | U |
PCINT3 |
PB3(17) |
pin-controlled interrupt | D |
PCINT4 |
PB4(18) |
pin-controlled interrupt | C |
PCINT5 |
PB5(19) |
pin-controlled interrupt | M |
OC1A |
PB1(15) |
TC1 - PWM output A | channel: R |
OC0A |
PD6(12) |
TC0 - PWM output A | channel: G |
OC0B |
PD6(11) |
TC0 - PWM output B | channel: B |
OC1B |
PB2(16) |
TC1 - PWM output B | channel: Lamp |
TOSC1 |
PB6(9) |
TC2 - input 1 | external oscillator |
TOSC2 |
PB7(10) |
TC2 - input 2 | external oscillator |
|
PD0(2) |
Battery | power indicator |
/RESET |
PC6(1) |
reset pin | reset |
To summarise, the microcontroller uses all three timer counters. Two of them are used to generate four PWM signals and one is used to support the external crystal oscillator.