Making Things Talk

78 MAKING THINGS TALK

Second, remember that serial data can be sent either

as ASCII or as raw binary values, and which you choose

to use depends both on the capabilities and limitations

of the devices you’re connecting, and on all the devices

in the middle that connect them. It might not be wise to

send raw binary data, for example, if the modems or the

software environments you program in are optimized for

ASCII data transfer.

Third, when you think about your project, think about the

messages that need to be exchanged, and come up with

a data protocol that adequately describes all the informa-

tion you need to send. This is your data packet. You might

want to add header bytes, separators, or tail bytes to make

reading the sequence easier.

Conclusion

The projects in this chapter have covered a number of ideas that are central to all

networked data communication. First, keep in mind that data communication is based

on a layered series of agreements, starting with the physical layer, then the electrical,

the logical, the data, and finally the application layer. Keep these layers in mind as you

design and troubleshoot your projects and you’ll find it easier to isolate problems

mode with ATUCL\r and following the same steps as

previously.

Because the AT commands are just text strings, you can

easily use them in microcontroller programs to control the

module, make and break connections, ...