Sending data more than 15MB to a server

Cellular Modules
1

Hi

I have a microcontroller connected to a LE910C1 - and want to send files up to 16 mb to our server. We can support both HTTP as well as FTP on our server.

While trying out the HTTP AT commands, especially with content type as multipart form, I realized that we need to have the file that we want to transfer on the modem - and not our microcontroller. This puts some constraints on us, as we found out the free size of the modem is less than what we need. Plus file transfer to the modem would add more total time to a file transfer - something we’d like to avoid on our battery-operated device.

The other approach we tried is to have FTP send a file by streaming bytes. We tried out the online mode, and it kinda works - but we see a lot of missed bytes. Even for a 1mb file. In the online mode, we have no way of knowing how many bytes were actually sent - so we have to wait for the complete file transfer before asking the FTP server for the file size, and then retrying. This whole thing takes a lot of time, and we have had very limited success with this.

The other approach is to send a file to our FTP server using the command mode - where after every send buffer, the connection is closed. And we are basically just appending to a file by making a connection every time we have a buffer to send. This takes up significantly more time for us.

What’s the best way to send a file to a server, when the files are 15mb or more? Is there a method I have missed here?

2

Hello,

Please add the AT commands you execute to better show the problem.
In general it should be possible to send multiple data chunks in the command mode with AT#FTPAPPEXT=bytestosend command and to indicate end of data with AT#FTPAPPEXT=bytestosend,1.
What interface do you use to communicate with the module - is it USB or RS232?
In case of RS232, maybe it is a flow control issue if you do not use the hardware flow control.