#!/usr/bin/env python

#======================================================================
# Program that polls data from Tecsis pressure display mod. 1929.300.
# Data is forwared to TCP server.
#
# The display has RS-485 interface.
# We've used a RS-232 / 485 converter from www.danbit.no,
# part no.: CNV232-485
# The converter is set to operate in half-duplex mode.
# RTS from PC wil control RX/TX function of RS-485 side
# of the converter.
#
# See documentation here:
# http://www2.geo.uib.no/equipment/seismic/airpressure_sensor/
#
# Dept. of Earth Science
# University of Bergen, Norway
# OM & JIS
# 11. Oct. 2005
#======================================================================

SERIAL_DEVICE = "/dev/ttyS0"
SERIAL_BAUDRATE = 9600
SENS_POLLINT = 0.2
DISPLAY_ADDRESS = 1
SENS_DESNUM = 2
SERVER = "your.server.name"
SERVER_PORT = 8080

import time, thread, serial, struct, socket


#----- This thread sends data polling requests at regular intervals

def Query():
	while True:
		ser.setRTS(1)
		ser.write("L%.2i:?*" % DISPLAY_ADDRESS)		# Command to poll ordinary data
		ser.flush()
		ser.setRTS(0)					# RTS control TX/RX on RS-232 / 485 Converter
		time.sleep(SENS_POLLINT)


#----- Initialize serial port and socket

ser = serial.Serial(SERIAL_DEVICE, SERIAL_BAUDRATE, bytesize=7, parity=serial.PARITY_EVEN, stopbits=1)

sd = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sd.connect((SERVER, SERVER_PORT))

thread.start_new(Query,())

data = ''


#----- Main loop ---------------

while True:
	data = data + ser.read(1)
	if data[-1] == '*' or data[-1] == '\n':
		value = data.split(':', 1)[1].split('*',1)[0][:-1]
		if len(value) == 5:
			value = int(value, 16)
			if value > 0x7FFFF:
				value = 0 - (0xFFFFF - value)
			value = float(value) / (10 ** SENS_DESNUM)
			value = "%.2f bar" % value
			sd.send(value)
			print value
		data = ''