Good morning, Mother!

by Dermot Tynan in Microtransat


Posted on Wednesday, August 21, 2013 at 08:00

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Debugging the low-level boards.


As of about an hour ago, Igor and Mother exchanged communication. It was awkward, stilted communication, like a first date, but they talked! One of the issues with the RS232 stream is that the kernel is chatty. I've suppressed a lot of the boot-up messages, but there are still all those /etc/rc startup messages. As the ALIX board only has one serial port, those messages are sent to Igor. To avoid sending Igor into a tail-spin, or more importantly, sending the boat into a tail-spin, Igor ignores all RS232 output when Mother boots, until the magic word is sent over the wire. The magic word is XYZZY. Anyone want to try and figure out where that comes from?

The protocol is quite simple. Single letter commands, followed by a newline, produce status. Commands prefaced with = and suffixes with one or more colon-separated numbers, will set a value. As Otto cannot talk directly to Mother, Igor must act as an intermediary, via the I2C bus. Overall, the idea is to try and give Otto as much space as possible, to just sail the boat. Igor worries about power, about communicating with Mother, and about interpreting the tilt-compensated compass.

So, time to write some Ruby code now, to encapsulate the Mother/Igor communication channel, and get the data to and from Redis.

Closer and closer, bit by bit...

On the hardware front, the keel plate is installed (finally!!) and the keel will be hung in place this weekend. Also, the final holes for the two steppers and the compass will need to be cut, and the hole for the rudder shaft (and shaft tube). Once those are done,the wiring harnesses for the external connectors, the steppers, and the compass, can all be added. After that, the deck plates can be glued into place and sealed with fibreglass tape and epoxy. This will mark another milestone as it will mean that the messy hull work will be completed, and I can start to install the electronics.


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