Sunset and Sunrise camera controller.

I have started a complete re-write for the STM32F103C8XX series using the Arduino IDE at stm32duino.com

http://stm32duino.com/viewtopic.php?f=19&t=380

Code is on github

https://github.com/pingumacpenguin/STM32-Sunrise/blob/master/STM32-Sunrise.ino

Prototype running a demo, switching the camera on and off with a mosfet, diming the display, displaying Sun up and Down times and the battery voltage and ambient temp from the RTC module. 

https://www.youtube.com/watch?v=r5jcgoYgfZs

One of the basic goals of this project (apart from the obvious... actually find enough time to complete it and more importantly... use it)... is to make the device out of jellybean devices, at the lowest price point possible.. 

There is no point in spending a fortune developing this, unless someone out there is daft enough to offer to  pump real money in to it, so with that in mind I decided to use a 5V Arduino Pro Mini clone, a Nokia 5110 LCD, and some recycled laptop batteries for the initial power source. 

I'm running the ProMini from the stock 16Mhz on-board crystal, and powering it from the raw input pin directly from the LiPo battery. Using a regulator makes no sense, as that would waste power.

This is slightly risk in the sense that the Atmel chip will be operating out of spec. when the Lipo battery drops to its minimum voltage, but my experiments on the breadboard (and other results from the internet) suggest that this is unlikely to cause problems. 

I'm also using a particular variant of the 5110 LCD board that has build in resistors which allow me to  safely run the LCD back light LED at 5V, but I will use software PWM to dim the LED, it makes the display more readable and uses less power.

Why software PWM rather than the Atmel hardware PWM... all will become apparent when I post a few pictures, but the simplified connection layout is the main reason.

The only modification to any of the boards, so far, is to remove the resistor for the power LED on the Arduino to save a few mA... this requires a steady hand, fine pointed soldering iron and a magnifier. Not rocket surgery, but it might be a little tricky for some. 

I'm soldering the 'duino clone directly on to the back of the LCD, using the supplied header pins from the 'duino, as this lets me control all of the pins to the display, and even switch it off completely, from software. It also greatly simplifies the build, and makes for a very compact device. 

The footprint of the prototype is the same size as the display. A few pictures will clarify this, and I'll post these soon. The RTC fits on the other side of the 'duino, and the whole thing is programmed with an external programmer, in my case a $2 USBASP USBISP AVR Programmer, in keeping with the low cost BOM.

Get it while its hot folks.. some functionality.. some wild speculation... lots of new and interesting bugs...  Try it here...

https://bitbucket.org/ya_433MHz/chdk_sunset_timer/src