Sunday, June 22, 2014

AVC 2014 Event Report

Or: Give Up! It's time for you to throw in the towel, capitulate and raise the white flag...

I made it farther than I did last time. I made it to the starting line. I turned on the robot, and watched it run straight as an arrow into the fence. It looked like it didn't even try to make the turn.

After that first run, I looked at the wiring and misread it. Since the LPC2148 is short on pins, all of the PWM outputs are multiplexed with other functions, functions it turned out I needed. PWM 1 and 3 are also UART 0, PWM 4 and 6 are also UART 1, and PWM 2 and 5 are also part of SPI 0. As it turns out, I needed all of those things, so I had to pick one to discard. I would have liked the GPS on UART 1 so that I could program the device over UART 0, but since that was the one thing that was possible to do without, I had to give it up. I had the GPS wired to UART 0, but only when it was in robot mode. When it was in bootloader mode, UART0 had to be connected to the host (through the FTDI cable). When I glanced at the board after the run, as I said, I misread it. I thought that the wiring was set up for bootloader. This would have made it impossible to do waypoint navigation. It would have resulted in the robot running straight as an arrow forever (or until it hit the fence).

As it turns out, it did try to make the turn. Like I said, I had misread the wiring and the GPS was fine. I could see from the logs that at about the right place it signalled to turn -100 (out of the full servo range of -128 to 127). It wanted to turn -600, but of course it was limited. I was let down by the steering mechanism again, but this time it wasn't a twitchy servo, it was my own circuit.

I was worried about running a solderless breadboard as the base of the robot controller, so I got some matching solder protoboards, but ended up never using them, mostly because I didn't want to commit the Loginator to this project. I didn't want to solder things down, so I ended up with two short breadboards stuck side by side. One supported the Loginator and FTDI socket, while the other supported the GPS interface and the opto-isolators for the servo control. The opto-isolator was the weakest part, partly from the sheer number of wires in such a small space, partly because I had to switch the channels at the last minute.

During the test run before the race, the thing was running long and seemed to want to turn only after I had picked it up. It might have already had this fault at this point. I have the logs and can analyze at this point. Soldering down the opto-isolator and its wires probably would have worked.

In any case, I was looking for an excuse to give up. It is one thing to surrender before you have to, and another to realize that there really is an insurmountable obstacle. During the test run on Friday, I had manually driven the thing around the track and flipped it on the finish line. The board popped out, but was apparently undamaged. I was almost hoping that the board was damaged beyond repair so that I could honestly say that I was beaten, rather than had given up.

I had convinced myself on Saturday that the steering problem was in the former  class. I had convinced myself that I needed to solder the whole thing to a board to get it to work. Thinking back on it now, if I had disassembled and reassembled it, it very well might have worked. I had the solder protoboard with me, and I could have borrowed a soldering iron. I could have done it there at the race.

This means I gave up too soon. I haven't finished. I will have to go back next year. Joseph is interested, so maybe I can use him as the motivation I need. Maybe he can help with Yukari, maybe he will help with another 'bot. Yukari is so close, I can feel it.

I did meet some nice people. Team Bloomberg was a dad with his family who had driven out from Wisconsin. Team Deep Space was an RC car with a robot controller, pretty similar to mine, except he went with odometry and a 4WD chassis. However, it had a cool hat, a flying saucer.

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