Ides of… Oh Crud, I’m Overdue


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. 😐