LOGOSOFT Teleservice

"Beam me up Scottie!" - preferably via GSM Teleservice to my LOGO!

OK - this is a long outstanding topic. Here I will give some of the info that I have found and hope that someone else can add some more detail or experiences. I have been looking for a solution to this problem for the past 4 years (off and on) and below are the 3 difficulties that I have come across.

1) 11 bit GSM modem

This is the reason always given, but I think that the other 2 aspects are also a problem. Most GSM modems only support 10 bit 'character framing' of 8N1 or 7E1 (1 Start bit, 8 Data bits, no parity, 1 Stop bit OR 1 Start bit, 7 data bits, EVEN parity bit, 1 Stop bit). Some of the modems you can send an AT command to it (via hyperterminal or in an initialisation string) to change this configuration. Some GSM modems even allow 11 bit communication on the RS232 side (PC & LOGO! side) even if the communication between 2 modems over the GSM network is 10 bit. There are many manufacturers of modems in the world, but most of them use the 'wireless module' or 'cellular engine' compnent from one of the following manufactureres
- Siemens (now Centerion: www.cinterion.com)
- Wavecom/Sierra Wireless(www.wavecom.com)
- Sagem
- Motorola
- Telit
- Sony Ericson (taken over by wavecom)

You have to check if these parts support the 11 bit protocol and their AT commands to change these settings

The LOGO! requires a more robust industrial character framing of 8E1 (1 Start bit, 8 Data bits, EVEN Parity bit + 1 Stop bit). The EVEN Parity is a small amount of error detection/correction.

There are some industrial modems that can do 11 bit (see attached zip file), but I have not purchased them or tested them yet and I do not know which module is inside each one.

2) Synchronous vs Asynchronous communication

3) Transparent vs non-Transparent data
It is best to give some info on this part with an extract directly form a cellular operator (also included in the zip document) - maybe this RLP protocol with the delays it introduces, upsets the communication to/from the LOGO ?!?!?

Non Transparent communication utilises a special GSM network-based error correction facility called "Radio Link Protocol" (RLP) that ensures more robust transmission.

What this essentially means is that the GSM network's IWU will add special error correction codes to control the flow of data.

This ensures that the data transmitted first obtains a special acknowledgement signal from the receiver that informs the transmitter that the data has been received as transmitted and that the receiver is ready to receive the next set of data from the transmitter.

If there is no such acknowledgement signal from the receiver, the networks will utilise their "data buffering" feature by using a special "forward correction" technique to ensure uninterrupted data transmission throughout.

Not all cellphones support GSM's Non Transparent (RLP-based) data capabilities.

Transparent data transmission means that there is no GSM error correction supplied over the air interface.

Non-Transparent data only applies to data transfers and not faxing since the Group 3 standard for fax transmission is a transparent protocol

OK, that is enough from me for now - please feedback with any clarifications, corrections or experiences with this.

UPDATE - just thought would keep the topic alive!
1) The DCD to DTR connection line has been incorrectly understood! This connection is so that the LOGO! cable (plug) can get power from either the PC or modem when the DCD line is kept high to power the MAX3221 optocouplers.
Therefore, the only communication lines are Tx & Rx

2) Therefore, all communication is ASYNCHRONOUS

3) The AT\N0 command IS IMPORTANT - it enables TRANSPARENT DATA, no matter what it is called. Therefore a GSM connection MUST support this, AND 11 bit (8E1). It looks like all GSM data comms is asynchronous anyway, so no more concern here

4) The INSYS modem will NOT support this, because it is built on a Siemens/ Cinterion module (TC35i)

5) The following manufactures and models look like they will support the necessary features
- MOXA OnCell G2100 or G21560L
- Wavecom/Sierra Wireless Fastrack M1203 or Xtend (or any modem based on a wavecom module inside)
- Telit GT864 & 863
- Westermo GDW-11 (FlyGT)
- Tixi HG20 or higher, but only with R-CON software
- Motorola G200 - CANNOT DETERMINE

I am still looking for more that might support LOGO! GSM Teleservice, but the final answer will have to be a test to see if it can be done with real devices.
Some of them are being sold very cheap (under 30 Euro) so I will see if I can get some!

Nobody interested in commenting?

LOGO!Barbarian

UPDATE - just thought would keep the topic alive!...

...Nobody interested in commenting?

Hello LOGO!Barbarian,

Just want to "comment" your expirience and knoledges. I don't know who could add something. Thank you for share all this information here. I hope that this is helpful. And for a one day your attachment was downloded 12 times. I think this is more then commnents. Keep Walking!

Best regards,

Hristo Mihalev