Hi all,


 

I don't yet have the dev kit, but I've been familiarising myself with creator, and checking out a bunch of datasheet and apps notes on psoc.

 

I've also broken my project down into bunch of hardware/firmware blocks and working out what the IO spread needs to be.


 

- LEDs and drive

- Piezo and drive

- Ambient light sensing

- 3-axis accelerometer measurement

- battery/charge system

- touch/proximity

- magnet detection


Photo 30-10-2013 5 19 02 pm.jpg


 

Once all of these are in place the will be an overarching set of state machines that should hopefully make it easy to tune features and usability on a prototype.


 

I have started looking at the light detector hardware:


 

- It has to have a reasonably fast response as I would be actively switching it on, sampling, then turning it off and sleeping, so an LDR is probably not the right way to go, a photodiode/transistor more likely

- It doesn't have to be all that accurate (as it'll just be referenced to a threshold based on something like 50-100 lux, ie. the difference between night and day), but it has to be precise, ie. the threshold needs to switch at the same lux today as it will tomorrow, so to that end I'll probably add some temperature compensation, I'm thinking the psocs internal temp sensor and compensation in code will be good enough for this if needed

- Using one of the psocs opamps in a simple current to voltage converter circuit feeding into the SAR adc seems ideal

- A good looking candidate for the photodiode is this guy: http://www.vishay.com/docs/81812/temd6200.pdf (SMD, small, ambient response, pretty cheap)


 

Cheers


 

A.