I'm looking for a couple of SPI and I2C components for a booster pack that I'm working on. The "requirements" are I would like to keep the costs down and have enough components on each bus to show how they work.
The goal of this booster pack is to be a playground for the signals that are available on the 40-pin headers with as little external test gear needed. I would prefer to only need a multimeter. Heck, it would be nice to do all the measurements on board but that might be too complicated for me at this time.
Here is what I'm planning on now:
- UART (menus and displaying output)
- RGB LED for 3 of the PWM outputs
- Servo for another PWM output
- 2 optical interrupts attached to the timer captures pins to measure servo rotation start and end
Those are the things nailed down. There are 7 analog ins that I was thinking of using as an on board voltage measurement (possibly the output of a digital pot or something like that) and 8 GPIOs that I'm sure I'll find a use for. Where I'm getting lost are the SPI and I2C capabilities. I have no idea what to attach to those busses (or even how to use them).
I see that there are 3 "CS" SPI pins which I assume are Chip Select which sounds an awful lot like an enable pin. If that is indeed the intent of those header pins, I have 2 out of the 3 with dedicated functionality. I'm thinking some flash memory would be a good option for the "other" CS.
I2C, well, there is a bus on the headers.... now what? Trying to find parts with the bus as the primary requirement isn't working out the way I hoped it would. In fact, it seems like I'm doing it backwards. I've toyed around with some DACs and ADCs but I have no idea what my requirements are beyond that. Are there some generally accepted standard parts that would be good for anyone getting into micros to learn? Would 2 components on the bus be enough to learn how to address each chip? Would feeding the output DAC into the input of the ADC be the worst "self licking ice-cream cone" idea?
I'm teaching myself electronics and micros, my intended audience for this booster pack is the same so any ideas should be pretty simple to implement and understand. I'm not looking for solutions, just component suggestions and some ideas. I would like to work out how to implement them on my own so I can learn how to use the data sheets, circuit design and board layout. I'm sure I will get stuck at some point and ask some questions later and intend on showing my work before the initial board spin.
Thanks for taking the time to read this.
Mac