30 Nov 08 The Robot – Progress and a Video

Well finally, here is the promised video…

The majority of the previous hardware issues have also now been solved which is good. The degrading CF cards was caused by a bad Alix board (I’d probably blown a resistor somewhere at some point). A replacement Alix board has arrived while I sell the other on eBay as faulty for any enthusiast who may wish to try and repair it. I am also using a SanDisk genuine SD card in an SD to CF adapter rather than some unbranded CF card. No filesystem errors and the disk now behaves as it should.

The motor controllers sometimes dropping/misinterpreting commands during heavy load was solved by a number of different fixes. Firstly, I believe with the USB to TTL converters the data lines are pulled up to 5v with a 4.7K resistor. I added a second 4.7K resistor in parallel to Tx to give the controller more of a chance against interference. I also added various smoothing capacitors, and edited my serial port byte transmit tool to restore the serial port settings graceefully on exit. Oh – I also cut the cables from their default 1m to the 12cm that I needed.. No more dropped commands.
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Tags: 4.7K resistor, alix, Alix board, DC to DC adapter, degrading CF, Linux robot, motor client, motor server, nc, netcat, parallel, sabertooth motor controllers, SD to CF adapter, smoothing capacitors, usb to ttl