Third model: The details

Hi folks,

some more details about the third Semitone model (code name "Diamond"):

The CPU (resp. microcontroller)
Because of the slight difference in the price I decided to develop the firmware for the ATmega32 in favour of the ATmega16. They are pin compatible. So it depends only on the requirements of the final firmware whether you can use the ATmega16 or -32.

The UART protocol
Having enough ROM, RAM and CPU time, I decided to implement a cleartext UART protocol, offering the user the possibility to use any serial communication terminal, or even a simple "echo" call from the commandline, to control the dimmer. This way, the applications can follow a very simple scheme for communication.

The output driver stages
Two output driver types are currently supported: TRIAC and MOSFET/IGBT. TRIACs can only be driven with forward phase angle control, MOSFETs and IGBTs can be driven with either forward or reverse phase angle control. The output driver options can be independently specified for each of the 20 channels.

The user interface
As noted before, the display will be 20x2 characters wide, with 8bit PWM (256 brightness steps) backlight. It features setup menus for all important functions, channel descriptors, etc. The dimmer will be controllable by RC5 infrared signals and by buttons and wheels (rotary encoders) on the front of the device.

There is still a lot to do for the firmware, but I'm working on it. Stay tuned for more news...

Have fun,
Mark