Echelon LonTal Stack - Manual (Page 214)

202 Appendix F: Appendix F
Downloading a LonTalk Stack Application Over
the Network
Overview
For a Neuron-hosted device, you can update the application image over the
network using OpenLNS or another network management tool. However, you
cannot use the same tools or technique to update a LonTalk Stack application
image over the network. Many LonTalk Stack devices do not require application
updates over the network, but for those that do, this appendix describes
considerations for adding this capability to the device.
If a LonTalk Stack device has sufficient non-volatile memory, it can hold two (or
more) application images: one image for the currently running application, and
the other image to control downloaded updates to the application. The device
then switches between these images as necessary. Because neither the LonTalk
API nor the LonTalk Host stack directly supports updating the LonTalk Stack
application over the network, you must:
1. Define a custom application download protocol.
2. Implement an application download utility.
3. Implement application download capability within your LonTalk Stack
application.
For the application download process:
• The application must be running and configured for the duration of the
download.
• There must be sufficient volatile and non-volatile memory to store the
new image without affecting the current image.
• The application must be able to boot the new image at the end of the
download. During this critical period, the application must be able to
tolerate device resets and boot either the old application image or the new
one, as appropriate.
This appendix decribes some of the considerations for designing a LonTalk Stack
application download function.
Important: This appendix does not describe how to download updates to the
firmware image into the Ecehlon Free Topology Echelon Smart Transceiver. It
only describes updates to the application image running on the host processor.
Custom Application Download Protocol
The custom LonTalk Stack application protocol that you define for downloading a
LonTalk Stack application over the network should support the following steps:
1. Prepare for application download.
When the application download utility informs the current LonTalk Stack
application that it needs to start an application download, the application
should respond by indicating whether it is ready for the utility to begin
the download. The utility must be able to wait until the application is
ready, or abort download preparation after a timeout period. The utility
should also inform the user of its state.