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Has anyone played with little GSM modules? Which one? How did it go? How hard was it?

Wonder what are the options for telemetry over GSM. I guess it would have to be GSM>TCP/IP on the internet, unless there are some serial P2P options via GSM/GPRS/2G/3G?

I'd say the simplest is to use wifi board (esp something) and connect it to wifi hotspot on any Android smartphone - no need to get extra sim, etc. However, that would still require you to have sort of a cloud and make your code connect to it to upload logs or to wait to connection, etc.

puff wrote:I'd say the simplest is to use wifi board (esp something) and connect it to wifi hotspot on any Android smartphone - no need to get extra sim, etc.

This sounds like a good idea for TCP/IP prototyping but extra point of failure, extra device extra pairing etc involved.

Vice versa, proving that it works would be even simpler: if you can open a website on your smartphone, it is highly likely that the devices connected to the hotspot have the connection. While checking the network coverage, connection status, errors (sms for balance? Indeed?) on a modem is a completely different story..

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We should have talked about this while I was there. I've done it with a plc. Key issue was getting a data plan that worked.

I've used them, they are fairly straightforward but you need to be somewhere were there is a reliable signal - not in the English countryside!

Any specific part numbers knows to work? Did you guys use them in TCP/IP or serial mode? If serial mode what was the destination?

I've used good old SIM300D via UART - worked like a charm

I've always been wondering, what does it mean "via UART"? How does it look like?
You use AT commands to set up a connection to some IP address? And then instead of AT commands you start sending your data?

puff wrote:I've always been wondering, what does it mean "via UART"? How does it look like?
You use AT commands to set up a connection to some IP address? And then instead of AT commands you start sending your data?

Yes. You can switch between data and command mode with special sequence or RTS/CTS or other flow control signal.
Or you can use some AT command (AT+CIPSEND IRC) to send some data in command mode. Data usually coded to ascii string.
Above is applied to GSM modules with integrated TCP/IP stack.

Dron_Gus wrote:GSM modules with integrated TCP/IP stack

does this mean GPRS? Is 3G any different?

puff wrote:

Dron_Gus wrote:GSM modules with integrated TCP/IP stack

does this mean GPRS? Is 3G any different?

GPRS, EDGE, LTE, etc. AT commands all the same. May be some differences between manufacturers, because AFAIR AT commands for integrated TCP/IP stack is not covered with any standard.

I used serial mode with a SIM900 module, it can be done with a USB-TTL adapter. I have also used TCP/IP with a 3G module but that was a complete system using Ethernet so it was a 'bolt in'.