1

I assume that I'll need a SIM Card

Atm I'm using this SIM9000A module connecting it at RXD/TXD pins and establishing ppp connection, however, it doesn't work very well, it takes about 5~10 seconds to ping google.es, and sometimes it doesn't even get response.

I don't know if it's caused by a low GSM/GPRS speed, or just by serial low speed, but AT commands work quick, later I'll test to load a web via AT commands.

Well, however, connecting it by TXD/RXD doesn't seem to be the best option, or maybe my module is not so good (it worth about $8). Should I look for another GSM module? maybe one that works on USB?

PD: Baud rate is 115200

PD2: I reside in Spain, afaik, that's relevant in most GSM modules, since I had to install a specific firmware to get it to work

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  • Does your area have a good GSM coverage? Do you get all the signal strength bars on your cell phone? – Dmitry Grigoryev Nov 7 '16 at 12:14
  • Looks like that module might use an antenna with an SMA connector. It may be worth looking for a larger/more effective antenna. – goobering Nov 7 '16 at 13:46
  • You should be able to get 1 Mbps reliably from the UART. Maybe twice that. Which is pretty slow internet wise. – goldilocks♦ Nov 7 '16 at 14:03
  • @DmitryGrigoryev yes, the signal in other devices is excellent – Mc Kernel Nov 7 '16 at 16:24
  • @goobering yes, it's SMA, but I think 7s average for ping is excesive even with that antenna... – Mc Kernel Nov 7 '16 at 16:24
2

I have several of these SIM9000A modules.

The problem with the slow ping is a bit strange? It should be less than 1 second, even more like 100ms.

The other problem is this module only supports GPRS (115kbs) if your GSM supports dual band GPRS (or 2.5G). Most networks do not support this any more (or are deliberately switched off because it affects voice) so your speed is only going to be a max of (57.5kbps) and even that is optimistic. I would say you are getting about ~36.6kbs. Ping should be good at these speeds but browsing modern websites is fatal.

It doesn't matter if you have 3G/4G or better in the area. The reason is that GPRS extends the GSM Circuit switch and the more people logged on within the area the slower things become.

So what is this module for then?

Well, at 8 bucks a piece its great for sending compressed JSON to servers for logging data.

  • Weather stations
  • GPS modules
  • Other sensors

Data that is sent infrequently. Most of the time using security SIM cards where you do not use more than 1 megabyte per month (which is allot of sensor data)

I want to browse the internet!

You can get a generic 4G dongle (better to get 4G even if you only got 3G so you are future proof) It seems like the most popular are Huawei because they are cheap. I have used many different Huawei 3G/4G dongles and they were very realible

enter image description here

You need to configure the Pi in the following way (You can use Rasbpian or Arch)

  1. Getting the Raspberry Pi to initialise the 3G modem dongle (and thus itself be able to see the internet)
  2. Getting the Raspberry Pi ethernet port configured to act as a DHCP server
  3. Getting the Raspberry Pi to relay internet traffic between the USB dongle and the RJ45 ethernet socket

If you just want it to have internet, Step 1 is enough. Steps 2 and 3 are required if you want to share that internet over LAN or WiFi.

It is best to use a powerd USB hub for this also becuase these dongles will want to use the full 500mA or more of power if available to run at full speed.

Search around the internet for some tutorials to find out how to install drivers and such and how to connect to the dongles and then route traffic the way you would like it.

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  • Indeed, it should be around 100ms, but for some reason, it isn't. maybe caused by a low signal? don't think so, it's too extremely imo, but I don't discard it. Maybe hardware limitations by my GSM module? Should I look for another one? I mostly will use it for sending data as JSON, but I would like to be able to play some youtube videos, with at least 480p quality – Mc Kernel Nov 8 '16 at 11:14
  • I think you should go and find a good deal on a data sim and USB at your local mobile shops. This SIM900 is not good for what you want. It is also to complicated to setup. A USB dongle just gives you internet via PPP, very easy. – Piotr Kula Nov 8 '16 at 11:16
  • Yea, it took me a long time to get it to work (poorly), but I prefered to do it by UART to save an USB port and space, I have to mount it in the 2Din car slot, which is kinda little for all the modules I plan to set, however, I will consider it and the powered USB Hub, thanks – Mc Kernel Nov 8 '16 at 11:21
  • Also, you can mount the USB hub somewhere under the dash, with a cable that goes into the Pi. So you can have easy access to USB somewhere (plus more ports) while not taking up space with your 7" screen that you want to fuse into your car. It is just a cable to extend out. – Piotr Kula Nov 8 '16 at 11:24
  • Sure, I already upvoted you but it have to be accepted since I don't have enough reputation now, sorry and thanks! – Mc Kernel Nov 8 '16 at 11:31

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