I'm using Lora 1276 and Arduino to collect data from here every nodes.
The example code I use is from here and it work successfully!
As far I know, LoraWAN is using TDMA to distribute the time to any nodes.
And polling by the gateway to get the data. That can make the nodes keep low power consume and let gateway to be control master.
I searched some information about preamble which is at the front of packet, nodes will decide whether to reply after received. If nodes receive a preamble that does not match,it will go back to sleep.
Is there any sample code for polling mode?
Thanks.
LoraWAN Class B devices do indeed use TDMA for scheduling periodic receive windows.
Here is sample code implementing Class B. https://github.com/Lora-net/LoRaMac-node/tree/master/src/apps/LoRaMac/classB
Related
I have some nodes with installed Xbee s2 on them. the zigbee modules configured as routers and coordinator, in zigbee mesh topology. I want to send data from each node to some other nodes.
question:
how I have to send data? here is a pseudo code that I have in mind. I want to know if there is any API in zigbee stack that I can use for this, and if I miss anything:
init_network;
fragment_data_to_frames;
fork();
if(process_is_parent)
for(i=0;iMbum_frames;i++){
send_frame(i);
wait(x miliseconds)// how much do I have to wait? or do I have to wait upon receiving ack,i.e. wait(ack(i));
}
}
if(process_is_child){
check_acknowledgment_packets();//does zigbee notify me that the frame is lost? or I have handle it by myself, e.g. by assuming frame is lost after specific time.
}
resend_lost_frames;
in the destination node, how I can retrieve the data? Do I have to handle it by myself by checking the sequence number and profile, and concatenating the packets? or Zigbee stack will do it for me.
XBee radio modules in API mode will generate a "Transmit Status" frame to indicate that a frame number was received by the remote module. There's no guarantee that the host on the other side successfully processed it, since it's a network-layer acknowledgement and not application-layer.
How much data are you planning to send? ZigBee was designed for low-speed, low-volume data transmission. If you're just using XBee modules, you can make use of their proprietary protocols (like transparent serial). For interoperability, you'll need to read up on the ZigBee Cluster Library and how it uses general commands and attributes to transfer information between nodes.
I have been trying to set up two XBees to communicate since the last three days. X-CTU seems to be the perfect option to do so, however, it is a real menace when it comes to discovering XBees on serial ports.
I was able to detect one XBee by luck just once and the other one never showed up. I have even replaced both my XBees. I am trying to figure out the alternative, i.e. using a serial console to perform the operation. I haven't been able to receive an OK response from the device upon issuing +++.
Since I haven't had a good experience using a PC to communicate with ESP8266 devices earlier, I tried to figure out a workaround by using the second Serial port of an Arduino to send such configuration messages and read the response by printing it out on the default serial console.
It also appears that configuration messages can differ depending on the mode of the device. If it's in API mode, the frame has to be generated in a specific format (I use the X-CTU frame generator for this purpose).
Why am I not able to receive a response from the XBee upon issuing a +++?
The devices are Series 1 XBees and the exact part number is XB24-AWI-001. Any help is highly appreciated.
Have you considered the XBee being in API mode? Maybe should you consider to reflash the device in AT mode to start playing with it.
To test if it's in API mode, you can refer to the guide, chapter 9 for the API mode structure:
http://eewiki.net/download/attachments/24313921/XBee_ZB_User_Guide.pdf?version=1&modificationDate=1380318639117&api=v2
Basically, a datagram in API mode starts with ~, and it's built as follows:
[0x7E|length(2B)|Command(1B)|Payload(length-1B)|Checksum(1B)]
As 0x7E is ~ on the ASCII table, you should try typing a bogus datagram in a serial terminal session like:
~ <C-d> AAAA
N.B.: The <C-d> characters means Control-d under unix., which is the EOF character.
Obviously such a message isn't likely to work, and you will receive a reply asking you to send that datagram again. That's because the EOF character being ASCII code 4, it means that the length of the datagram will be 4 bytes. So then you send four bogus bytes, the checksum will be A, which is very likely to be right, and the receiver will assume the transmission has been corrupted. So the datagram will be asked again, meaning you will receive a datagram to do that query.
Though I can only advice you to consider running it only in API mode (more reliable and a better API, but you cannot play around with it and understand what's going on by tapping on the line with a logic analyzer… though giving enough time, you'll start to read API datagrams like it's English ☺).
I wrote a page with a few resources to check on how to reflash the XBees:
https://github.com/hackable-devices/polluxnzcity/wiki/Flash-zigbee
and here's other advices from another totally unrelated project:
https://github.com/andrewrapp/xbee-api#documentation
And I also wrote a lib (aimed at beaglebones but you can tweak it for your use) that handles API mode 2 with XBees:
https://github.com/hackable-devices/polluxnzcity/blob/master/PolluxGateway/include/xbee/xbee_communicator.h
https://github.com/guyzmo/polluxnzcity/blob/master/PolluxGateway/src/xbee/xbee_communicator.C
but I bet with a little google search you can find more widely used libraries than those ones, and even some aimed to be run on Arduinos (N.B.: that lib was originally written for Arduinos, and then adapted to run for Beaglebone, so reversing the operation shouldn't be hard).
My application can send and receive data independently on COM Port (9 pin). Now the scenario is that, the destination device while sending data can also request some data. Now, in that case my application while receiving the data from the device, would have to send the requested data as well. So the question is, is it possible conceptually to send some data while receiving data from the same COM port ?
Note: If this is not the right place to ask this question, please let me know which SO site is apt for this.
Sure it is. The RS232 is a full duplex interface, hence there are two independent channels for each direction.
But note that these two channels are different pins of course. You cant send and receive on the same pin with the RS232 (Although it is theoretically possible to transmit and receive data over a single line simultaneously - but not in this case).
I have a GSM ModeM connected to a serial port, and I use it so send SMS upon certain events.
Since it is not Plug-and-Play, I am confused as to how I'll detect its connection status. Win APIs like GetCommState will obviously not work.
I could periodically send packets of data and check whether the data is being consumed or not, but I'm wary about the risks of polling over performance and clogging up the buffers which might be in use.
So, is there any other method, or some interrupt based thing, which I could use to check whether is still connected, via a serial port, to my system?
I'd be grateful for any help on this.
Thanks.
From Windows 7 onwards, use Windows Mobile Broadband API to get information about a GSM modem.
Serial ports are very primitive communication devices, they date from the very early days of computing. It is what you plugged your ASR-33 teletype into to start banging in your Fortran program. The only reason they are still around is because they are simple, hardware vendors like them because they don't have to spend money developing and supporting a custom api to use their device.
Still, even back in the sixties did a computer have a need to find out if a teletype was attached. Which is done through the hardware handshake signals. The DSR signal, Data Set Ready, is turned on by the device when it is powered up. If you use the .NET SerialPort class then you can check that signal with the SerialPort.DsrHolding property. If you use the winapi then use GetCommModemStatus(), MS_DSR_ON flag.
That still only tells you that some device is attached. If you want to find out that it is the modem that you wrote your program for then you can interrogate it with AT commands, a protocol that's specific to modems. No vendor implements this exactly the same way but you can usually count on an identification from the modem with the ATI command. Check the programming manual for the modem for details.
I am using a 16-bit MCU PIC24HJ64GP504 to write a CAN based application. Basically it is communication between my board and one another node which continuously keeps on sending data to my board using CAN at 1 Mbit/s. I am configuring the ECAN module in my PIC24 to work at 1 Mbit/s. I have written the code in such a way that for the first 10 ms the ECAN module will accept all messages coming in from the other side and after that I have re-configured the ECAN module to accept only those messages with message ID 0x13.
Now here comes the issue... The other node and my board are powered up at the same instant. The other node starts transmitting messages after 40 ms or so after powerup. But I am not able to get any message from it on my board. Now if I power up my board first, give it some time to reconfigure the ECAN module with new filters and settle down and then power up the other node, then everything works perfectly.
Now the strangest part... If I have a CAN bus analyzer connected between my board and the other node and even if I power up both the nodes at the same time, everything works fine... No need to power up my board first. I have tried this with three different bus analyzers from different manufacturers and got the same results.
To me it appears that during re-configuration of the ECAN module, it takes some time to settle down. And with the introduction of the bus analyzer in the bus, this time is somehow cut short so that everything works perfectly. But I am not sure what exactly the problem might be.
The problem might be a missing ACK. The CAN-Analyzer might acknowledge frames and the device does not switch to error passive.
I would hold off sending until the whole bus is initialized.
Also sounds like missing ACKs to me.
Are you seeing any error frames (get the scope to trigger off 6 consecutive dominant bits) - the Tx node might be going off the bus or even into some application-error mode if it doesn't get acknowledged enough.
You might be able to coax it back on bus by transmitting a dummy message on the bus.
I've found a Saleae Logic very useful in these circumstances (as well as a scope) - hang it off the Rx pin of your physical layer (or even wire up a standalone PHY that you can use to monitor the bus). The Saleae software will interpret the CAN and show you what's happening. Sometimes it's useful to use the scope trigger out to trigger the Logic.
CAN Communication requires at least two active devices on bus to have successful communication. This is because, a CAN frame is not completed unless someone acknowledges it.
When you power up your board and other node, it seems your board is not getting ready in 40msec. If it is not ready, it leaves "Other node" to be the only member on the bus and voilates above stated rule. Other node will get Tx error and after 128 erros, That other node will go in error mode and stop sending messages -- Hence you are not getting anything.
When you power up your board first, give it time - your board is ready and will ACK every message sent by other node -- Hence communication is good!
When you add CANalyzer, even if your board is not powered up, there are two active nodes on the bus -- Hence communication is good!