Capture screen output from chat script to log file

I have a CHAT script that works in interactive command terminal to turn on a USB modem and displays the output from talking to /dev/ttyUSB0. Need to capture the output from the screen to a file and the standard redirects have not worked so far. Also need to configure CRON script to run the connect and disconnect scripts at a certain time from reading a file for start time and frequency. Eventually would love to control this from a Python program interface, but SUBPROCESS calls cannot capture this screen and error messages so far.