AIS baud rate

[jemsea]

In attempting to hook up my Milltechmarine AIS engine to a new chartplotter I have discovered a slight problem. Somehow the output baud rate is at 9600 and should be 38400.

Both Milltechmarine and Standard Horizon have been helpful but I lack the computer understanding to get the process required to work.

I'm hoping someone can direct me to someone in the Annapolis area that may have the knowledge. Below is the an email describing the process:

In order to change the baud rate, you will need to run putty or Hyperterminal to enter the command to set it to 38400. Given the unit is currently set at 9600 you will need to configure putty or Hyperterminal to 9600 baud on the correct com port (same com port as the one you are currently using for your nav package). You also need to make sure the nav software is not running at the same time. Once there, enter the following commands:

i38400<enter>

q<enter>

Cycle the power on the SR161. Change the baud rate on the terminal program to 38400 and connect again to the SR161. Type <SPACE> and then <ENTER>. You should see the settings information displayed back to you. Exit the terminal program.

Next, run the nav programs and change the baud rate in the nav program to 38400 and you should be set.

Also, be sure to see our page on Milltech Marine AIS Chart Plotter Reference which includes instructions and wiring diagrams for connecting to a chart plotter and computer.

Documentation etc. can also be found on: Milltech Marine Customer Resource Center.

Thanks for any help.

[hanschristian38]

They have given you instructions for a task only accomplished by someone with experience on serial communications formerly used between a dumb terminal and a computer.

A major issue not covered in their instructions is the type of cable used between the terminal emulation device and the AIS device. This will be some type of serial cable with either a modem configuration or a null-modem configuration. You will also need to check the number of pins - 9 or 25 used at each end for the serial connections.

Sorry - I am not near Annapolis. You are correct that you will need assistance if you have not worked with dumb terminal communications in the past. The manufacturer should have a better method of resetting the communications speed.

[jemsea]

After yesterday I feel like I have at least a dumb terminal operator...

[rodney_k]

I've been through this exact same process - Standard Horizon chartplotter, and Milltech SR161 receiver. A regular serial cable from your laptop to the sr161 will work... I believe the receiver comes with a serial cable, you could use that. Do you have hyperterminal on your laptop?

[jemsea]

Thanks for the reply. My problem is the the SR 161 somehow is operating at 9600 baud and needs to be reset to 38400. I am having a problem getting the reset process on the computer to work.

[Beausoleil]

John,

Since you're posting here, you obviously have access to a computer. If it's Windows XP-based AND it has a 9-pin serial port , you can use the included Hyperterminal application as mentioned before. If you happen to have a laptop with USB ports only and no serial port - do yourself a favor and find a local geek who can help you. If yours does have a serial port, then proceed:

You can find Hyperterminal under "All Programs" -> "Accessories" -> "Communications" -> "Hyperterminal". When you start the program, it may ask you if you want to make Hyperterminal your default telnet program - go ahead and click "yes" for now. Then it will attempt to create a new connection and ask you for a name and to choose an icon for it. Call it "direct" and choose any icon. Click "Ok". It will then ask you for details for the phone number you want to dial. This shows Hyperterminal's heritage from the late 80's - before the Internet as we know it - when it was one of many terminal programs used to dial via modems to various BBS's and Compuserve, AOL and Prodigy. Just click on the "Connect using" field, and choose COM1 (hopefully if your computer has a built-in modem - most do - it's configured to use COM3). Then the phone number fields go gray (don't allow input), so click "Ok".

Next pops up a window asking you to set the bits per second - set it to 9600. Data bits should be left at 8, parity none, and stop bits 1. Flow control should probably be left to "hardware", but can be changed to "Xon / Xoff" or "none" if you can't connect to the AIS. Click "Ok". Hit the enter key a couple of times and see if you get a prompt from the AIS. If not, go back and check your settings by clicking on "Call" in the menu bar of Hyperterminal, then "Disconnect". You can then check your settings by clicking "File" on the menu bar, then "Properties", then the "Configure" button.

Then you should be able to try the "i38400" command to change the bit rate, and "q" to save the config and quit.

Sorry about all the details, but that's Windows for you... If you have Vista, then Hyperterminal may be located somewhere else under the Start button. If it's a Mac, I don't know what they use (perhaps you can use the Unix terminal emulator program "tip"?)

FWIW - "baud" rate is a misnomer from the old days. Bauds are the number of signal changes per second, and with old modems - up to 2400 bits/second, the modem actually encoded bit per signal change (Hertz), but that went out the window with modern modems. They used fancy bit encoding schemes which could represent 2, 4 or 8 bits per signal change (or symbol). Modern v.92 modems can represent 7 bits per symbol, sampled 8000 times a second, for a bit rate of 56,000 bits per second. Needless to say, the term baud doesn't cut it any more, since you can cram an awful lot of bits into a baud nowadays! Sorry, to my ears someone saying "38400 baud" is about as bad as fingers on a chalkboard!!!