Talking to the instrument and adjusting baud rates

• Plug the USB-serial converter into the computer and find the corresponding port:

ls -ltr /dev/tty* | tail

The last line has the name of the keyspan port. Let’s say it is

/dev/ttyUSB0

• Basic communication to the instrument to find the communication baud rate:

  • Open tk_terminal.py

  • In port/device, change to

    /dev/ttyUSB0

  • then

    File/Connect to port

    Command/Send Break

  The following answer means the communication was successful:

[BREAK Wakeup A]
WorkHorse Broadband ADCP Version 50.35
Teledyne RD Instruments (c) 1996-2009
All Rights Reserved.
>

If there is instead an error message then

File/Disconnect

change the baud rate in baud and try again until it works.

This is the communication baud rate.

• Next, we need to know the data baud rate

  The data baud rate is the rate at which the data are downloaded. In general, the longer the cable, the slower the baud rate required to avoid errors, hence the slower the downloading. With RS232 protocol, excessive length will not just slow down communications, it will introduce unrecoverable errors (the only solution is to shorten the cable)

  To find the data baud rate:

  • plug in the instrument with the cable you want to test
  • record about 10 min of data if there is none already
  • download the data with the highest baud rate possible w/o downloading error.

  To do so,

  • quit tk_terminal
  • edit the appropriate python file (e.g. ladcpwh300.py)
  • enter the communication baud rate from above
  • guess a data baud rate (start with a high value, eg 115200)
  • enter the serial port (from above) in device_dn, eg. /dev/ttyUSB0 for the usb keyspan
  • execute the python program python wh300.py and download the data.

  If there is a problem, lower the data baud rate and try again until it works

Note: If the intrument gets stuck, unconnecting to the instrument

might not be enough but powering it down by manually unplugging its power cable might do the trick.