[Tutor] Pen plotter data format

[Phil]

This is probably an off-topic question but I cannot think of another 
group that may offer any help. All of the Python software is self-written.

Briefly, my laptop reads a gcode file and extracts the x any y 
coordinates into two lists (one x and one y). The pen-up and pen_down 
commands are not currently saved. The laptop then sends the x and y 
coordinates to the micro-controller one at a time until the lists are 
empty. The controller expects and waits for three bytes of x values and 
then three bytes of y values in that order.

I'm thinking that a better approach might to send an x byte, for 
example, like this "x, 123" and have the micro-controller separate the 
value. Currently, the micro-controller only accepts data and moves the 
motors and doesn't perform any processing.

Something like this might be better:

if cmd starts with 'x';
     strip off the coord value
     run the motor to that coord

if cmd starts with 'y':
     etc

if cmd starts with 'z':
     lift or lower pen

I'm still not sure how the laptop should handle the 'z' (pen-up) 
commands because they don't fit neatly into the same x and y pair 
pattern. Maybe the laptop should just parse the gcode file one line at a 
time and then send the complete line to the micro-controller for 
processing until the end of the file is reached? That would mean that 
all sent bytes would have to be the same length but I could add padding 
as I'm currently doing.

I don't know what format pen plotters normally receive their data in and 
I'm hoping that someone may know. An Internet search hasn't helped so far.







-- 
Regards,
Phil