roland_plotter_flowcontrol.py

#
# roland_plotter_flowcontrol.py
#
# chunks hpgl commands into 256 bytes. feeds plotters new chunks
# when there is available space.
#
# expects plotter at /dev/ttyUSB0 9600 8N1
# 
# tested with a roland dxy-885
#
# usage:
#
# python roland_plotter_flowcontrol.py < plot.hpgl
#
# say hi! github.com/rfb rfb@skyscraper.nu
#

import serial
import sys

contents = sys.stdin.read()
chunkSize = 256
chunks = [contents[i:i+chunkSize] for i in range(0, len(contents), chunkSize)]

def currentBufferSize(ser):
  ser.write(b"\x1b.B") # hey plotter, how much buffer is remaining?
  size = int(ser.read_until(b"\x0d").decode().strip())
  print("currentBufferSize:",size)
  return size

with serial.Serial('/dev/ttyUSB0', 9600) as ser:
  ser.write(b"\x1b.M100;;;13:") # plotter, terminate responses with chr 13!

  for chunk in chunks:
    while currentBufferSize(ser) < chunkSize:
      print("holding..")
  
    print("sending", chunk)
    ser.write(chunk.encode())