My quadrotor helicopter project has had some rough times. I am now two years into its development. I designed a lot of it from the ground up, most of it in electronics and software. The cost so far has been somewhere between $500 and $1000, but I have no way of recuperating that cost or explaining it to my parents. However, I experienced something extremely aggravating in the past week.
Two weeks ago, I decided to switch the main controller from a PIC 18F2550 with 28 pins in SPDIP to its bigger brother, the 18F4550 with 40 pins in PDIP. It’s supposed to have identical hardware, but when I ported over my Wii Nunchuk reader code (I’m actually not supposed to link the public SVN, but I can do whatever I want >:D), which uses the MSSP module for hardware I2C communications with the Nunchuk, the communications ceased to work. I added some debugging code, and found out that the MSSP module on the 18F4550 simply sucks compared to the one on the cheaper 18F2550. Whereas I could get a rock-solid stream of data with the 18F2550, the bigger chip, even after days of careful tweaking, was squirrely and only read data out in unpredictable bursts.
Needless to say, I am now stuck with fewer pins than I need, and expansion will be difficult, if not impossible. The long range radio communications module may need to be multiplexed with the Z-axis gyro’s SPI interface (which is software-based ATM), and I honestly have no idea how I’m going to deal with the ultrasonic rangefinder (for maintaining height).
Just had to rant for some reason. 😐