Telegesis (UK) Limited
TG-ETRXn-UG-01-103
29
User Guide
1.04
ETRX1 and ETRX2
©2008 Telegesis (UK) Ltd
ETRXn User Guide (Rev 1.04)
could be used in conjunction with function 0019 to send switching commands to another
device and receive feedback.
Using simple digital logic blocks this application can be extended to serve more than just a
single switch and also serve more than one actuator to present feedback. The switch
application shows four modes of operation which are both versatile and cover many
possible applications without the need for a host microcontroller.
10.3 Serial Port Replacement
Where you need to control a number of devices using RS232 or RS485 (e.g. in an industrial
automation scenario) and you do not want to wire up your production line all you need to do is
connect the serial port of a module to your end device. The coordinator can open a channel which
the end device will accept by default and send the required data. After receiving the required
feedback the coordinator can close the channel again and talk to the next unit.
Any prompts on the remote side can be disabled using the extended function registers S07 and
S08, so the remote end would see nothing except a transparent link.
Mesh networking is very reliable for automation in industrial environments as reliability increases
with each device added into the redundant mesh. This overcomes one of the great shortcomings
of point-to-point radio in automation.
Telegesis have also assembled the ETRX2 module into units with a USB (ETRX2USB) and
compact flash interface (ETRX2CF), which is very suitable for connecting to laptop computers and
PDAs without an RS232 port.
10.4 Using a Host Microcontroller
Using an inexpensive host microcontroller with an on-chip UART you can greatly extend the
possible applications of the ETRXn wireless meshing modules. The input buffer of the ETRX2
module is 128 bytes, and as no command is longer than that, no buffer overflows can be expected
during normal program operation. For this to work it is important to wait for feedback after the
execution of a command, i.e. do not issue a new command until you have received an “OK” or
“ERRORxx” prompt.
When using a channel there are no limitations to the payload, so a buffer overflow can occur when
sending too much data at once or where the recipient is temporarily out of reach. To avoid a buffer
overflow XON/XOFF or hardware handshaking should be used.
10.5 Custom Functionality
If you find that you have an application which you cannot solve with the predefined functionality
supplied, and you do not want to use a host microcontroller for every device, please contact us
about the extension of the functionality required to fulfil your needs.
Telegesis is also happy to offer custom firmware development for the ETRX2 range of products.
10.6 Developing Your Own Firmware
11 Feel free to develop your own firmware to go on to the ETRX2 and
use the modules as hardware only. In order to do that you need to
