Echelon LonTal Stack - Manual (Page 215)

LonTalk Stack Developer’s Guide 203
During this stage, the LonTalk Stack device should verify that the
application to be downloaded can run on the device platform (using the
FPGA ID or similar mechanism), and verify that the application image is
from a trusted source (for example, by using an encrypted signature).
2. Download the application.
A reliable and efficient data transfer mechanism should be used. The
interoperable file transfer protocol (FTP) can be used, treating the entire
application image as a file.
The download utility and the application must support long flash write
times during this portion of the download process. The LonTalk Stack
application should update the flash in the background (see Download
Capability within the Application), however, it might be necessary for the
protocol to define additional flow control to allow the LonTalk Stack
application to complete flash writes before accepting new data.
3. Complete download.
The application download utility informs the current application that the
download is complete. The LonTalk Stack application should verify the
integrity of the image, and either:
a. Accept the image, and proceed to the final steps below.
b. Request retransmission of some sections of the image.
c. Reject the download.
4. Boot the new application.
To boot the new application, you must implement a custom boot loader
(or boot copier) so that the embedded processor can load the new
application and restart the processor with the new image.
Important: For the duration of the first three steps, the application must be
running, the LonTalk Host stack must be started, and the LonTalk Stack device
must be configured.
Application Download Utility
This tool needs to read the application image to be loaded, and run the
application download protocol described in Custom Application Download
Protocol. You can write the utility as an OpenLNS Plugin or as any type of
network-aware application.
Download Capability within the Application
Your application must implement the custom application protocol, and provide
sufficient non-volatile storage for the new application image. The application
also must tolerate time consuming writes to flash during the transfer. At a
minimum, the LonTalk Stack application should reserve enough RAM to buffer
two flash sectors. When one sector has been completely received, the application
should write it to flash in a background process. If the write is not complete
when the second buffer is filled, the LonTalk Stack application must tell the