User's Manual

 Look for All Errors. Be sure your program is trapping all possible

error conditions that the Base Station may return to you. The list

includes:

Sequence Errors detected

Illegal Command detected

Base Station Initialized

Addressing a Terminal Not Signed In

Command without an ID

All of these error conditions are detailed in the next chapter. Don’t

forget to program for them; this is a common mistake. Failure to

trap them will give create very strange, unpredictable results.

Even though you don’t think your code will ever make a mistake,

take advantage of feedback that the Base Station provides. Failure

to do so is a common mistake that eventually results in serious

program failure, sometimes due to hardware problems that go

undetected.

 Parse the Returned Strings thoroughly. Don’t assume anything

about the next response from the Base to your program and look

only for the partial string such as the ID only; parse the string

returned completely and be sure you are examining every

possibility. Failure to do so is a common mistake.

 Plan for expansion. You may start small (1 base/1 Terminal) but

try to create an application that will allow for easy expansion and

addition - especially of Terminals.

 Use the Demo Programs. The demo programs can at least allow

you to see how the system functions and whether you can

anticipate any system-wide problems. The demo programs should

also be used as a response-time benchmark.

Failure Planning

Hardware Failures

Let’s assume that each part of the system has failed. How are you going to

know what has happened and how are you going to recover?

 The most frequent failures are at the Terminal level. If a Terminal has

a hardware failure, it will not be able to SIGN OUT. It is possible for

the Terminal operator to press the ON/OFF key or the F1 key by

accident, forcing the Terminal to SIGN OUT - sometimes in the

middle of a transaction. This happens at battery-changing time also.

You need to plan for partial transactions - do you trash the data you do

have and start over, or pick up where you left off?