I've scoured the internet and can't find anything that will fit my needs.
I am trying to figure out if it's possible to set up the PI as a client with a FIFO and have the server read from that FIFO. I have an array of PIs and so I need to have some kind of buffer on the pi, and then need to pull the data off of it.
It does not appear pymodbustcp offers a FIFO option. Are there any other options? It doesn't have to be over TCP, I'm just more familiar with the IOS layers than serial communication.
Related
My question is regarding an ESP8266 board and the ESP-touch technology.
ESP-touch uses the length field of a UDP package to broadcast wifi ID and PW through a device (like a smartphone) to the chip (like in my case ESP 8266).
I want to turn this around, more specifically:
I want the ESP8266 chip to broadcast UDP packets with some sort of identifier-number in the length field of the UDP packet, without beeing connected to any wifi connection. Then these UDP packets are recieved by an app on a smartphone so the identifier-number can be extracted and used on the smartphone.
I am relatively new to this topic and do not know if this can work.
When I try to find any information online they all say that the first step is to connect the chip to a wifi. But I don't want that. The smartphone and the chip don't know each other and are not connected in any way. So I want this type of "broadcasting" so that the smartphone can recieve the package without really beeing connected to the chip.
I guess there must be some way to make it function like I explained above, but I can't find a way how this can work.
I don't need the chip to send UDP packets explicitely, it can be any type of package. I took UDP packet as an example because there is already the ESP-touch technology which is more or less similar.
The important thing is that the package that I send has a field where I can put some identifier-number in (not encrypted), which can then be recieved by another device like a smartphone where this identifier-number is extracted.
For clarification: I don't need to use ESP touch or anything related to that. I only stated this technology as an example. I just want to achieve the behavior stated above and in the picture! :)
This is an example picture how I want it to work:
No, it's not possible to send any packages without being connected to the network. ESP-touch or TI Smart Config or similar technologies utilize Monitor mode. As the name suggests, in this mode one can listen for packages, but can't send them.
ESPNOW provides data flow between ESP devices without connections via router. It is another feature of the Espressive API. There are tutorials for ESP8266 and ESP32...
https://randomnerdtutorials.com/esp-now-esp8266-nodemcu-arduino-ide/ .. https://www.instructables.com/ESP32-With-ESP-Now-Protocol/
I'm doing a security analysis project on an IoT device that uses an unencrypted BLE connection (with ATT protocol) and I want to spoof an individual BLE packet with the source address of an already connected device. Is there some tool or API that would allow me to do this easily? I've already tried gatttool and spooftooph but they seem to be connection based and don't allow you to send out single packets with modified fields (as far as I could tell).
You will need some hardware where you can access the radio peripheral directly. What you basically need to do is to find or write a ble sniffer firmware, with the modification that it at a given moment sends a packet on the connection it is currently listening to. But note that the signal strength must be stronger than the original device's signal so it doesn't interfere.
The only open source project I'm aware of is Ubertooth. You will also be able to do this with an nRF52 but then you need to write your own sniffer firmware since Nordic Semiconductor's is closed source.
I can't comment on Emils reply yet, < 50 rep:
Nordic Semis nRF Sniffer v2 needs only the nRF52DK and wireshark to work as a general BLE sniffer. At 40$ it's not that expensive. I know for a fact they will release a new dongle soon that will sell for ~10-15 bucks if you can wait a a month or two.
I am trying connect multiple Arduino Mega Boards via their Serial pins to allow communication between the boards. I want to be able to connect an arbitrary amount of arduinos by daisy-chaning them and I want one board to be the master, taking control over the actions of the other boards. The master should be determined dynamically by the boards. I am aware that the daisy chaining method introduces delays to the communication due to the forwarding of packets, but so far I am planning on connection 4 boards at most. In the future this might increase to maybe 10 boards. My boards all have a separate power source, since they are connected to some other hardware which has its own power source.
My idea was to connect the boards in such a way, that the master would be determined by the wireing of the boards. I thought about having the "Serial" port as 'To-Master' serial port and the "Serial1" port as "To-Child" serial port. The boards send hello messages on the "To-Master" serial port and the master replies if it received such a message on the "To-Child" serial port. If no answer is received after some seconds, the board determines itself to be the master.
I wired the boards up by connecting the ground pins, and wiring RX1 of the master to TX0 of the child and TX1 of the master to RX0 of the child:
Basically my setup is working, since the boards do detect each other and exchange hello messages and replies. There is however a significant amount of packet loss or corruption which I would like to eliminate.
As a simple measure of packet verification, I begin each packet with a "magic number". The receiving board looks for this byte and only tries to read a packet after receiving this byte. Any other bytes received are simply discarded.
As it seems, it happens quite often that something is received on either serial port that does not start with the magic number and is therefore discarded. The timestamps of these events are however consistent with the timestamps of sending of the other board meaning that the packet was at least partially transmitted but somehow the magic byte got corrupted or discarded.
Is this a known problem with the arduinos serial ports?
Can it be related to my wiring?
Are there any measures I can take to ensure a save delivery of the packets?
Can it be a problem of the boards not reading the signal at the correct time (I used a baud rate of 9600)?
I also looked into I2C communication, but I did not find any resource or information if it is possible to dynamically choose the master for this type of communication. Also in the documentation it stated, that it is important that all devices share a common power source which is not possible in my scenario. However, the basic master-slave principle of this I2C conforms with my requirements, as I have a master that sends commands to all other boards. Could I2C be utilized in my case?
Thank you for your thoughts!
Here is a discussion about multi-master I2C topology of Arduinos, seems that it is supported (haven't tested it myself). - http://forum.arduino.cc/index.php/topic,13579.0.html
You can test SPI as well, here is a comparison between the two - http://components.about.com/od/Theory/a/Selecting-Between-I2c-And-Spi.htm.
Slave might be selected with generic GPIOs
I don't know any known implementation of multi-clients on top of Serial bus (usually it is intended for peer2peer communication only) - even though, your configuration seems reasonable, I would be considering other options.
BTW, from your comment about different power sources, I assume your boards are away from each-other. Have you considered very cheap ($2) RF modules, such as nRF24L01+ (http://maniacbug.wordpress.com/2011/11/02/getting-started-rf24/). THere is a library for networking those in multi-node network
Might be better off with I2C or SPI like people have suggested here.
However, to address your question directly, it is most likely wiring. I am assuming you are using cheap jumper wires to plug directly into the Arduino Headers. Noise on this connection is the most likely problem or garbled serial messages. Try implementing with twisted pair cables and connecting directly to the board.
SPI or I2C might have better error correction than your customer serial protocol. I would see the other answers for that.
I am working on a project which requires data to be sent FROM PC TO FPGA,which processes the data and sends it BACK TO PC.
The board I am using is Atlys™ Spartan-6 FPGA Development Board.
The data is to be sent as 1 byte , because 1 byte is processed at each rising edge of the clock.
Could you please suggest me ways of sending data to FPGA ?
Thanks
Pick some method of communication that you have access to IP (intellectual property) cores for. For example, if you can readily access a UDP/IP core for your FPGA, then use that. If you have to develop the HDL yourself, serial protocols (UART, I2C, etc) will be simpler blocks to write. In general, HDL takes longer to develop, debug, and test.
UDP has some advantage because you can use tools like Wireshark to capture packets on the PC (once you get past the initial hurdle of actually getting packets to/from the FPGA). Plus, many people are familiar with UDP in various programming languages (C, C++).
In any case, you'll probably spend time with an oscilloscope and logic analyzer checking out signal levels and timing when data is sent to/from the FPGA.
I currently have an embedded device connected to a PC through a serial port. I am having trouble with receiving data on the PC. When I use my PCI serial port card I am able to receive data right away (no delays). When I use my USB-To-Serial plug or the motherboards built in serial port I have to delay reading data (40ms for 32byte packets).
The only difference I can find between the hardware is the UART. The PCI card uses a 16650 and the plug/motherboard uses a standard 16550A. The PCI card is set to interrupt at 28 bytes and the plug is set to interrupt at 14 bytes.
I am connected at 56700 Baud (if this helps).
The delay becomes the majority of the duty cycle and really increases transfer time. (10min transfer vs 1 hour transfer).
Does anyone have an explanation for why I have to use a delay with the plug/motherboard? Can anyone suggest a possible solution to minimizing or removing this delay?
Linux has an ASYNC_LOW_LATENCY flag for the serial driver that may help. Whatever driver you're using may have something similar.
However, latency shouldn't make a difference on a bulk transfer. It should add 40 ms at the very start of the transfer and that's it, which is why drivers don't worry about it in the first place. I would recommend refactoring your transfer protocol to use a sliding window protocol, with a window size of around 100 packets, if you are doing 32-byte packets at that baud rate and latency. In other words, you only want to stop transmitting if you haven't received an ACK for the packet you sent 100 packets ago.
You'll probably find that different USB-Serial converters produce different results. We've found that the FTDI ones work well for talking with embedded devices. Some converters seem to buffer the data for a long time and/or fragment it.
I've never seen a problem with a motherboard connection - not sure what is going on there! Can you change the interrupt point for the motherboard serial port?
I have a serial to usb converter. When I hook it up to my breakout box and create a loopback I am able to send / receive at close to 1Mbps without problems. The serial port sends binary data that may be translated into ascii data.
Using .Net I set my software to fire an event on every byte (ReceivedBytesThreshold=1), though that doesn't mean it will.