Need some inputs


#1

Hello,
I have a requirement and wondering if any one out here can help me by sharing your thoughts and suggestions.

I have a plain embedded device (no OS, no protocol stacks etc.,) which logs data.
I would like this data to be periodically offloaded to a server for analysis and archive.
I am wondering if there is any product (perhaps a GPRS Modem) that can help connect the device to a server
(via an internet service provider) and transfer this information (perhaps as a file through FTP).

Please share your thoughts on a cost effective way to build this solution?
What Wavecomm products can be evaluated? and what other minimal components (hardware, software) would need to be integrated?
As an example, can I initiate a FTP like transfer with the help of a GPRS Modem from the embedded device? Where would this FTP software be available? Wavecom modem?

thanks and regards
Raman


#2

Hiya,

You really should be talking to a Wavecom Distributor about this.

However, I have done this using a Michrochip PIC as the host processor and using a Wavecom Fastrack modem with the WIPSoft application installed. This configuration let me use AT commands from the PIC (via a serial connection) to upload data via GPRS.

ciao, Dave


#3

thank you Dave. Sure that is one of the options.
I was thinking, this forum might help pose some thoughts on the feasibility and the how before I go there…

thanks again
Raman


#4

Hiya,

Other (more complicated) options:

  1. Use the Wavecom module as a pure GPRS modem - but this requires PPP/TCP etc in your controller - and you said you can’t do that.
  2. Write an application in OpenAT that runs on the Wavecom module to upload your data. Treat your embedded device as a slave that just supplies data to transmit (more difficult - you will need to learn OpenAT to go this route)
  3. Simply use the Wavecom module as a standard modem and make a data (not GPRS) call to your server. Transfer the data using XMODEM or one of the other BBS protocols. Advantages: no apps for Wavecom Module; could use any generic modem. Disadvantages: using Circuit Switched Data (CSD) Call - max 9600 baud and potentially expensive; lot of overhead in embedded device to set up data and transfer (slightly more than GPRS/WIP method); and you require a receive modem on your server + appropriate software.

BTW, I’ve also done a data transfer system using option 3 - but it was done using CSD rather than GPRS because of an anomaly in the cost of the telephone services…

ciao, Dave


#5

Though still significantly less than doing your own TCP/IP stack!

Note that It doesn’t need to be a GSM modem - any modem will do.

but it is the nature of modems that you need one modem, and one “phone line”, per connection - this is where IP really scores if you need something scalable…


#6

thank you dave, once again for your comments, and thanks awneil.

Option 1 - using the GPRS modem and its capability is what I am exploring. I was trying to understand if TCP/IP is needed over and above the AT Command interface at the MC end. My conclusion is that they are needed, and wavecom GPRS modem just provides the media access. This leaves me back at my drawing room, but that’s ok. One additional question if you don’t mind.
At a higher level, the steps needed are:

  • establish a GPRS PDP context through a GPRS modem
  • set modem to data state
  • establish a PPP over the modem serial port
  • invoke an FTP or similar utility that runs over a TCP/IP socket ( which means, besides a GPRS modem attached to the MC, I need PPP, TCP/IP and FTP running on the MC)
    Is this right?

thanks again for posting your comments

regards
Raman


#7

Incorrect.

Wavecom supply a TCP/IP stack that runs in the modem, and is accessed via AT commands - so you don’t need a TCP/IP stack on the PIC.
(in fact, most GSM/GPRS module venodors do this in one form or another)

The Wavecom stack includes HTTP, FTP, and SMTP in addition to the basic socket access - it is called “WIPSoft”


#8

thanks awneil.
that is encouraging…
I will explore WIPSoft and try to figure out the AT commands

thanks much