Saturday, October 20, 2007

UCB Talking

I got the X,Y and Z chips programmed and soldered up the Universal Controller Board. I followed the instructions dutifully and everything went well, up until I tried the third test. This should have brought up the Stepper Exerciser screen. Instead, I got a series of error messages in stdout, all saying:

sendMessage error - retrying

I tried jumpering the serial lines for loopback and the screen came up. It told me no devices were present but that's what I expected. At least I knew the serial drivers were working correctly.

OK, maybe the X chip didn't get programmed correctly. I swapped it for the Y chip. It started working (yay), then stopped (boo). Same error messages.

Poked around online to see if I could find others with the same problem. Didn't find anything helpful. So, I resorted to my standard fallback strategy for debugging: poking around a bit.

With the stdout screen churning out its error messages, I started to prod the board, looking for bad connections. I touched something and the exercise screen came up. OK, close it and try again. Figured out that touching pin 18 kicked the chip to life. Traced pin 18 to the Sync connector, which wasn't installed yet. Also R11, also not installed yet. So the Sync signal was floating.

Went back to the forums and searched for R11. Yep. The test often fails without R10, R11 and P3 installed. Rather than install them, I just shoved a couple spare resistors in and jumpered p3 with a piece of wire.

That got the UCB talking consistently. Tried the X, Y and Z chips. All worked correctly.

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