Having fun hacking with embedded systems and learning a few things in the process.
Saturday, October 9, 2010
Focus on What Matters
So I've started getting things together for Episode 3 of the series in which I intent to get SD card functionality working. I quickly got sidetracked and thought it would be useful to mention it. This seems to happen a lot in projects. We let our minds get 3 or 4 steps ahead and we start thinking about details that don't matter now and may never matter but trying to plan for everything slows us down. This is a fine line to try to walk. If you don't plan ahead enough you can really hurt yourself in the long run or make things more difficult. If you plan too much you spend a disproportionate amount of time on ideas or details that may never matter. This has happened over the past couple of days. I started with what matters, getting SD card functionality added to the sensor platform. Then the details set in. SD needs 3.3V instead of the 5V I'm getting from the programmer not to mention the programmer can't source enough current required for SD communication. So I need a power supply. What kind of a power supply do I need? How will I know if the SD stuff is working. I need some sort of debug output. Should I hook up a temporary LCD to debug with? Maybe USB to output to the computer. I got bogged down fast in the details.
So I decided I was getting too wrapped up in future details. What mattered was getting SD card functionality. I don't need to decide on the power circuitry right now. I just need enough power to get SD working. A USB port can source 100mA without adding communication protocol. That is pushing it so let's just use a wall wart to be safe. Most of us have a box of them lying around anyway and we can refine the power stuff more in the future if we want but the wall wart will get us the power we need right now. As far as confirming the SD stuff is working with an LCD screen, that is overkill. We need to confirm that the PIC can read and write to the SD card. Well, I think I have a simple enough way to do that with just the LED we've already added. Stay tuned for Episode 3 where I'll go through the whole process.