I am using an embedded microprocessor to communicate with a SIM900 GPRS modem. The sim900 has an embedded tcp/ip stack but no embedded PPP stack, and my embedded environment has neither of these stacks.
With other devices I have followed these steps:
at+cgdcont="IP","internet",,
atd*99***1#
called a PPP function that took take care of the login to the APN (and presumably the authentication & LCP etc).
called a TCP function that connected to the remote server.
But now I have to do the PPP part myself. so I am at a loss locating all the necessary information.... can anyone point me in the right direction?
when I use hyperterm so as to see what happens with ATD*99***1# it connects and returns a lot of PPP frames which i suppose i have to write a module to deal with. But I did notice, on a number of sites, that the login to the APN is not mentioned at all, so is there a way of bypassing the login?
When I follow the example in the SIM900 docs, I get an error indicating (quite rightly) that the PDP is deactivated...
I think my original question was really 2 questions...
1) does one need to write an APN logon module when using the onboard TCP functions of the GPRS module?
- the answer here is NO. The module takes care of that....see cmd AT+cstt="apn","user","pwd".
2) where can one find opensource code for a PPP stack?...that remains unanswered.
The 1.4.1 release and some older versions of LWIP have an implementation of PPP in it. Not certain if it can easily be used standalone though. You might still be able to decouple it from LWIP and use it.
Related
I am involved in a project where we have some kind of IoT device. An nxp processor with an LTE modem on a PCB. The software running on it connects to the modem over a single uart interface. It will initialize the modem through AT commands, and finally made a data call to the provider (PPP).
Then, it uses lwIP (light weight IP) to open some mqtt subscriptions, and allow user code to make http get/post requests to our servers.
Every 15 minutes we want to retrieve signal strength from the modem and report this back to the server. What I do now, is put the modem back in command mode, retrieve the signal strength info, go back to data mode, and resume normal operation.
The round trip from data mode, to commando mode, and back to data mode takes several seconds (4-5 ish). This is annoying, because during that time we are not receptive for commands.
I've read about gsm mux 07.10. By following some defined protocol it allows to create virtual serial ports, over one physical uart. That sounds nice, although I realize this will go at the cost of performance (bytes will be added to each frame we send to either command mode / data mode).
The gsm mux 07.10 spec dates from 1999. I am far from an expert in mobile solutions. I was wondering: is muxing still the way to go? How does a typical smart phone deals with this for example? Do they include modems with more than one uart to have parallel access to AT commands and a live internet connection? Or do they in fact still rely on gsm mux?
If somebody would be so kind to give some insights. Also on potential C libraries that are available that implement gsm mux 07.10? It seems that TinyGSM implements it (although I can't seem to find where), and I also can find the linux kernel driver that implements gsm mux 07.10. But that driver is written on top the tty interfaces in linux, so that would mean I would have to reverse engineer the kernel driver and strip out the tty stuff and replace it with my own uart implementation.
First of all, the spec numbering is the old GSM specification numbering, so those old specs will never be updated, the new specifications with new numbering scheme will. I do not remember when the switch was made, but I do remember someone at work giving a presentation on 07.10 probably around 1998/1999, so probably a few years after that or around that time (and definitely before 2009).
The newer spec numbering scheme uses three digits for the first part.
So for instance the old AT command spec 07.07 is now 27.007, and the current 07.10 multiplex specification is 27.010.
The following is what I remember of 07.10.
The motivations for developing 07.10 was to exactly support the kind of scenario that you describe. Remember back in the mid 90's, if mobile phones had a serial interface then that was RS-232 though each manufacturer's proprietary connector at the bottom of the phone. One single serial interface.
However, in order to use 07.10 mux in serial communication you needed to install some specific serial drivers in Windows with support for 07.10 (and I think maybe there was some reliability issue with them?), and for that reason 07.10 never took of and became anything more than an rarely used solution.
Also by the end of the 90's additional serial interfaces like Bluetooth and IrDA became available on many phones, and later USB as well, which both added additional physical interfaces as well as natively multiplexing within each protocol.
So the need for multiplexing over physical RS-232 became less of an issue, and whatever little popularity 07.10 ever had dwindled down to virtual nothing.
Fast forward a couple of decades and suddenly someone asks about it on stackoverflow. Good on you :) As far as I can tell I cannot see any fundamental problems with using it for the purpose you present.
Modern smart phones that support AT commands will most likely have a code base for the AT command parsing with roots in the 90's, which most likely include the AT+CMUX command. Of course manufacturers today have zero explicit wish for supporting it, but when it is already present it will just come along with the collection of all other legacy AT commands that they support.
So if the modem supports AT+CMUX you should be good to go. I have no experience or recommendation with regards to client protocol libraries.
I have the following: STM32F407G-DISC1. My goal is to communicate (sending strings back and forth) between my pc and the mcu over serial and I currently am able to do so using the micro-usb (otg) port, while powering separately using the mini-usb st-link port (so using two cables).
Is it possible to use the mini-usb port for serial communications? (eliminating one of the cables)
I have read the user manual and my interpretation is that this is not possible without physical modifications. But I am a beginner and would like to verify I am correct in this interpretation. I have researched thoroughly however most sources seem to not refer to this specific board and it is my understanding with the newer version of st-link it uses this should be achievable.
It is possible - just send the messages via the USART2
You need to solder those two wires as they screw up the design.
I'm really having trouble connecting to my ESP8266. I was working with this setup for long time now and I didn't have to flash my boards. Now after having to use a different wifi i needed to flash the board. After doing the following
Updating to the newest ConfigurableFirmata
Using FirmataBuilder to download fitting firmata
Uploading the Firmata to the ESP8266
I can't connect via Johnny-Five anymore (getting the usual timeout error). I couldn't narrow down what it exaclty is (and I have been trying all day) but these are things that I have noticed (Using ConfigurableFirmata directly as well as using firmatabuilder and StandardWifiFirmata, all with the same behaviour)
an open Hotspot gets created even though I'm in Client Mode
when scanning for ports I do find the Module connected to my Wifi (Serial Monitor in Debug tells me the same too) but no open port is found, even though it's specified in the firmata.
I just can't narrow down the reason. I hope you guys can.
OK,
this was a simple user mistake. But since I lost a whole day searching for the error and I think others might too, I'll share my mistake here.
As I pointed out I created the Firmata as Client (thinking its a client to my Hotspot). But you will have to create it as a server (as you want to connect to the board)
It's as simple as that. If you are on http://firmatabuilder.com/ make sure you choose TCP Server if you want to connect to your board.
Firstly, I'll just give you a brief introduction about our project... its "Speech controlled Home Automation System" where we are controlling the Home appliances by the voice or speech commands. We're successfully done with the voice recognition module. But our problem is with achieving the communication between the transmitter {where the user gives the voice command} and receiver {where the home appliances are present} through WiFi i.e. we have got 2 ESP8266 12E modules interfaced with Arduino both at the transmitter and receiver side and these two WiFi modules need to be communicated(To interchange some data sent by Arduinos).So please let us know which Arduino code need to be used at transmitter side wifi module and at Receiver side wifi module and also about the header files or additional softwares(if any)to be used.
you can achieve this by starting one of wifi modules in Access Point Mode and the other one has to be set to Station Mode in order to connect to the first one.
In case you want to add a router, just set both ESP8266 modules to Station Mode and connect them to the router.
And then transfer any data you want through AT commands of ESP8266.
Here is the refrence to them.
https://room-15.github.io/blog/2015/03/26/esp8266-at-command-reference/
If you are newbie to Esp8266 and Arduino , this will help you.
http://www.teomaragakis.com/hardware/electronics/how-to-connect-an-esp8266-to-an-arduino-uno/
Good Luck !
I worked on a similar system a year ago. I was developing a remote controlled toy. My main difference was I used the ESP8266 without an Arduino attached.
One ESP worked as a a WiFi hotspot and the other connected to it, sending messages through UDP.
For some reason, I could not get the two ESP modules to connect (I think it was a problem with the board I had), but I sent messages from my computer, and it worked out fine. I will not burden you with all of the code, but here is the GitHub link.
All that needs to happen is they will be on the same WiFi network, and then you can use the ESP8266 WiFi library to send messages between the two. Like I said above, I used UDP, which is good for high speed, with no error checking. But there is also TCP (higher up, has error checking code), or you can use the server/client part of the library to set up a full web server and read/write data to it. Without knowing what type of data, I cannot comment on what would be the best method.
As for headers, you will need WiFi.h, and if you are using UDP you will need WiFiUdp.h
You should not need any external software besides the Arduino IDE.
I taught myself from scratch for this product, using two main resources: the Arduino library reference, and the docs on the ESP8266 Arduino GitHub page
I have a project which the information from the microcontroller (drop rate changes of dextrose like sending notification "nearly empty" or "Sudden change of drop rate. Drop rate of 15 automatically return to 14") would display in an application in a computer. I am thinking of using ZigBee and it would be responsible for transferring the information but I am new with the technology.
Does anyone could help me how to program the ZigBee module? I have seen some articles saying that it could be programmed in eclipse CDT. I am bit confused how to get start.
Any help would be appreciated. Thanks!
Use USB Explorer device (or similar) to enter a serial terminal session on the receiving XBee.
Type ATMY to get the receiving XBee's address. Write it down.
Put the sender in the USB Explorer and type ATDL plus the receiver's address, like "ATDL798A728"
Type ATWR to save this setting.
Attach sender XBee's UART (TX and RX pins) to microcontroller.
Plug receiving XBee into USB Explorer attached to computer.
Run Processing sketch or similar to read from the serial port.
The two XBees will run by default in 'transparent mode,' which pipes data coming into one UART out of the other UART, exactly like a wire. So when your microcontroller writes data into the sender XBee, it will come out of the receiving XBee and be read (and displayed or whatever you need) by your software.
It really depends on how much configuration your installation can handle. Is this a one off installation, or a "system" of products you want to make that have to be able to work together in whatever configuration they're bought?
As already explained, xbee modules that have the whole radio + stack already setup and working for serial data are simple to use for the trivial case of you sending out a few pre-paired setups form the lab, or even site installation by an expert.
If your embedded devices have to find each other automatically, then you'd need a way to get the embedded microcontroller to get the modules discover each other, make a connection, and then have the application code in the embedded microcontrollers talk to each other and identify what they need to do with each other.
In this case, you probably would be better off with the (upfront much more complex and likely expensive) design where the zigbee stack is inside the embedded controller, so your application code can use it properly to control connectivity.
The TI zigbee pro evaluation kit is very comprehensive, and seems great to me so far. It sounds like you're at the point where you need to spend some money and get some experience with real modules, just to get a feel for the technology. Though be warned, you may need IAR embedded workbench to work with these long term, and that's pretty expensive software!
Alternatively, Atmel have a pretty interesting looking zigbee implementation with their "bitcloud" software platform (free zigbee pro stack!! woo! and they have a free ARM toolchain!) but I've found the getting started info around the bitcloud stuff is really lacking, and while I can get the code setup and compiling, I'm not confident to buy enough of their evaluation gear for a zigbee pro mesh network to test it in real life yet.
PS: if you're getting started with short range wireless, i can't recommend this book highly enough. http://www.amazon.com/Essentials-Short-Range-Wireless-Cambridge-Series/dp/0521760690/ref=sr_1_2?ie=UTF8&qid=1336091059&sr=8-2
It contains very good introduction to the different technologies available, and the strengths and weaknesses of all of them (and wireless in general) Plus it will leave you in a good position to start understanding the features you really need for the system you're designing.
some of the zigbee/xbee modules simply behave as wireless serial, no programming required just turn them on. Others require programming. It depends on what your needs really are. the ones that behave like wireless serial have an AT command set if I remember right so you can adjust some things, like for example if you want more than two (more than one wireless point to point connection) you can specify which two talk to each other...