Archive for April 2008

Still too warm for a feature freeze.

I have finally got round to changing my LCD control software to 4bit operation so as to use fewer port pins and in doing so it occured red to me that it would me very daft to have an LCD display and not use it for the main function menu (I was planning on having a bunch of LEDs give out a binary number and a control knob to select the mode but on reflection that’s just stupid!!). So once again is back to the coding/drawing board. Mind you had I thought about it before maybe I wouldn’t keep having theses little drawbacks….

When words fail you, make some up…

For those who are interested in the wonders of CNC (probably none of you) I thought I would write a quick post to describe wht i have done so far.

AS mentioned here the control board has been replaced and I am controling everything with VB Express 2008. Here is a little more detail

The protocol for the machine

The reason the people who built this machine originally used both parallel and serial comms was because of the amount of data to be transmitted. so to do the same over a single serial link will require some packing. Unfortunately there is no standard way to do this, so therefore there is a requirement for me start by writing a protocol to handle all this info. The basic idea is to use the serial port like an 8 bit wide parallel port. Each byte is then an instruction. The prelim spec for the control protocol is here in OO format. if anyone actually wants to read this in MS Word .DOC format let me know and i will convert it.

After being able to communicate with the machine i needed to write some code to send commands to the machine and, more importantly, create lines and arcs from which everything else can be created. So i wrote some code to implement Bresenham’s line and arc algorithms and then wrote an XML based machine control language (since i am not a G-code fan, i think it is a bit out of date). Once i work out how i am going to do Post the code without it being mistaken for HTML i will post a sample programme in this post but until then you can see the programme that made this drawing here (simply open with notepad)

any more data wanted or people wanting to help develop this software, let me know

What the whoby whaty?

I just noticed that there have been a spike of hits on my site. After a little snooping through the stats i see that slashdong gave me reference. It looks like someone has been reading what i write. Apologies for anyone else who was waiting for the next instalment. I will try and post some more stuff about the progress as things get done. Comments welcome (they let me know that people are in fact reading this stuff since most of my stats say that the visiting browsers are just search engine robots).

coming together!!

Sorry for the lack of posts but my adventure into the world of CNC machines took me of at a slant so here is progress on the two projects. (Also no one is commenting so i don’t know if anyone is actually reading this or whether i am just wittering into the cyber darkness.)

Almost all written and just waiting for a PCB to be made and the last little bit (the electromyography bit) to get working. I’m attempting to build an EKG to start with since that’s easy for me to test and then i will just change the probes and the software for the final version (and possibly the gain of the input amp) The PCB will hopefully be made on my nice shiny new PCB router once i can get it working. It does a very good job of ploughing all the way through the board or just compliant at me at the moment. The breadboard prototype is now looking like this and there’s more to add (also just noticed that the serial port 9pin D-sub has fallen off in that pic but it shuould be hanging off the MAX232 there) . Most of the parts for the beta model have been bought including thisrather swanky box (the red one) which requires holes to be made in it for controls which will hopefully be done with my Boxford Duet now that i have finished the first attempt at the software.

CNC controllerScreenshot 1
cnc-file-maker.JPGScreenshot 2

Its all still moving along. It will be finished one day….

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