"""
  This is some code for communicating with a Delta-Tau PMAC motor 
  controller as used at SINQ from python. Python 3 is assumed and 
  tested. We use the ethernet protocol of the Pmac. This code benefits 
  from the SICS driver for Pmac which in turn benefits from the driver 
  written by Pete Leicester at Diamond.


  Usage: python36 deltatau.py  pmachost:port command
         Then returns the response for command. 

  Mark Koennecke, October 2019
"""

import struct
import socket

def packPmacCommand(command):
    # 0x40 = VR_DOWNLOAD 
    # 0xBF = VR_PMAC_GETRESPONSE
    buf = struct.pack('BBHHH',0x40,0xBF,0,0,socket.htons(len(command)))
    buf = buf + bytes(command,'utf-8')
    return buf

def readPmacReply(input):
    msg = bytearray()
    expectAck = True
    while True:
        b = input.recv(1)
        bint = int.from_bytes(b,byteorder='little')
        if bint == 2 or bint == 7: #STX or BELL
            expectAck = False
            continue
        if expectAck and bint == 6: # ACK
            return bytes(msg)
        else:
            if bint == 13 and not expectAck: # CR
                return bytes(msg)
            else:
                msg.append(bint)

if __name__ == "__main__":
    from sys import argv
    addr = argv[1].split(':')
    s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    s.connect((addr[0],int(addr[1])))
    buf = packPmacCommand(argv[2])
    s.send(buf)
    reply = readPmacReply(s)
    print(reply.decode('utf-8') + '\n')