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Message Routing

This example shows a real example of both updating modem firm ware for older 3AS and Epic modems(to the latest as at Sep 2005) and designing a solution for an application that has a boat operating along the shoreline talking to a base station on land. 

There is a need to extend the range of a base station but there is a hill in the way. A repeater station is installed on the hill and therefore extend the range of the boat.

However, depending on the location of the boat, some of the time the it can talk directly to the base station and other times by the repeater station, so by using the message routing (over hop) function, the modem on the boat is able to identify when it has received a message from the base station that is ultimately intended for it but not yet given to it by the repeater.  The modem buffers the message and waits to see if it sees the repeated message in which case it will send that message to the RS232 port or otherwise, if it times out, and does not see the repeated message, it sends the one given to it via the base station to the port.  In either case only one message is sent.

The attached files should all be downloaded to the directory in which the SaTerm executable is located on your PC.

Examplel.spf is a first pass at the required message routing setup

The 4 .smf files are used by the message routing setup function in SaTerm

The .sff and .sf2 files contain the updated firmware for use in flash update of the radio modems

The first step is to complete the configuration of the Source Routing Project.

  • Run SaTerm
  • Select Mode – Routing Setup
  • If the design window is empty select File – Open Project – and open Example.spf
  • You should now see a design window containing 3 modem icons (Base, Repeater and Boat) with arrows joining Base to Repeater and Repeater to Boat.
  • Double click on the Boat Icon to display the Properties table
  • The Terminal Address will need to be set to the Hex value of a fixed character which will appear in each RTCA data packet.
  • Frequency, TxPwr Level, RxThres. Level, Port 1 Speed, Port 1 Data, Port 1 Parity should all be checked and corrected as necessary
  • Click [OK]
  • Repeat steps 5, 7 and 8 for the Base and Repeater modem icons.
  • Right click on a blank space in the design window
  • Set Address Offset and Length so that the required fixed character (as in step 6) is flagged as the address. (note character 1 is offset 0)
  • Click [OK]
  • Select File – Save Project
  • Now we need to take the laptop, with a programming cable, to each modem in turn.

The modem firmware must first be updated (if necessary)

The latest Epic should already have software v3.16 installed (if this is not the case flash update to v3.16 will be required)

The older Epic and the 3AS will both need to be flash updated to v2.26. Refer to chapter 8 of the SaTerm user guide. This is normally a very simple and straight forward procedure but please ring me if you have any concerns.

Finally the routing setup parameters must be transmitted to each modem.

a. Repeat steps 1-4 (above)

b. Attach the modem and enable programming mode

c. Double click on the modem icon for the current modem

d. Click [Transmit values]

e. Repeat for each modem

 

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