As per the previous post (which was 5 years ago), I have a  that has three forms of serial communication. One is an RS232, the other is USB A and finally a USB B. So I have three options to connect my PC to this device. The device sends the scanned RFID tags through this serial connection to my PC. I want to place the reader 60 meters away from my PC. Which type of serial communication should I use?
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What is the maximum length of serial cable I can use, to connection work properly? Is length of serial cable in connection with baud rate? I am using about 5 meter cable at speed 38400 bauds and RS232 communication, is it too long?
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I'm making my second USB design, but the D+/D- pins on the MCU (atemga16u2) aren't in the right order for the micro B connector. What's the best practice for routing these to go the right way? My current idea is to rotate the atmega 180 degrees and route them under, but it feels like the traces are fairly long. I could also drop one of the lines under the other, but I'm sure that would mess with the lengths for the differential pair. This device won't go over Full Speed, so I can get away with less than perfect routing.
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I got the  in order to interface with an I2C peripheral through a USB port on my Windows 7 computer.  The VCP drivers seem to install correctly, and a COM port is assigned to the module, and can be opened by a terminal emulator. However, I cannot seem to get any signal in or out of the module. That is, I see no activity when I send data through the port, or receive any data when I connect an I2C device to it (this was debugged using a scope). I have also verified that the RESET isn't on.  I found very little helpful information out there on how to get this module to work, so if anyone has experience with it, or with similar FTDI modules, my question is: what are the steps that I need to take in order to get the module to communicate?
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For a project, I like to use 3.5mm type USB connector. This is for a closed system therefore I am not worried about USB approval but I am worried for signal integrity and insertion/removal problems.   Are there any common 3.5mm 4 contact point USB connectors that I can safely use? What is the usual practice for these connectors?
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I am assuming the answer would be yes since Tx/Rx pins are used to send data back and forth, or is it of such a low frequency that such thing is not required?
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I'm using a Magic Mouse with my MacBook Pro and Mountain Lion. The cursor sometimes start to lag. I figured, the reason for this could be the distance between my Mac and the mouse (about 1.5 meters / 5 foot).   I bought an external USB Bluetooth dongle I want to plug into my monitor on my desk, so the mouse is closer to the controller. However, I can't figure out how to make OS X use the external dongle instead of the built in controller.   When I go into System Prefs > Bluetooth and hold the Option key to display the reception, I see that it is the strongest when it's next to my Mac and not when it's next to the dongle. So what can I do to change that? Thanks!
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I'm trying to determine which battery to use for my application. I'll be using a class 1 or class 2 Bluetooth (not low energy) module, which requires about ~50/60mA of RX/TX current. In addition, there is a microcontroller and some low power analog IC's. I require a continuous stream of data from the device for 1-10 minutes.  Are coin cells completely out of the question? I'm talking about CR2450 Lithium-ions. I don't really mind if they don't last long, but will they work? Because in my application, size is key, and battery life is a trade off that I'm willing to make.
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Alright so I have computer currently with an Inateck "SuperSpeed" PCI-E expansion card with 4 USB 3.0 Slots.   Now we need about 16 pieces of hardware plugged into this machine from a far distance. Our current setup is USB 3.0 Extender that gets its own power that connects to a USB 3.0 hub where each has 3 to 4 additional USB 3.0 slots. Now imagine that for each of those 4 slots. The problem is, it that it is extremely unreliable. If you turn on the machine with everything plugged in we get the blue screen of death. Instead we have to plug everything in, in a very specific order. So that all 16 pieces of hardware are read.   Is there limits to what I am trying to do here? The computer is a simple Dell Inspiron 3650. Is the problem with the motherboard that comes on this machine?  If so what might be some hardware components that I need? Or maybe just point me into the direction of a motherboard that might be able to handle this kind of pressure.
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I'm looking for a good link to data from Microcontroller to computer. I do not know what kind of communications is suitable for me.  I need a link which has a bit rate more than 50 Mbit/sec. and also it should be good enough reliable.  Moreover, I have not chosen the uC yet. What about these choices?   1-(uC side) USB to USB (PC side)  2-(uC side) SPI to USB (PC side)  3-(uC side) ethernet to ethernet (PC side)  Data is in fact received from a 16 channel ADC with a rate of 100 K. Data is processed in the uC and then would be sent continuously to PC.
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I'm currently developing an internet of things device that utilizes a uBlox SARA-U260 gsm/3G modem.  In field testing, we have had significant software/firmware issues due to poor cell phone reception in our deployments in sub-saharan Africa.  I'm having a hard time duplicating the problems in the lab because the cell reception here is too good.  Even if there is no antenna plugged into the modem, it is still able to connect to the cell network internet!  So, I'm looking for the best way to thwart my modem into thinking it has bad reception.  One thought I had was to cut the coax cable of the antenna and solder a resistor between the gnd shroud and the center conductor.  Would this work?  What size resistor would make sense? Probably a fairly low-value resistor (say 50 ohm?)  I'm confused about why the modem can still connect even without an antenna.  I thought that during normal operation the modem must short the ground and center conductor when it is transmitting (hence the high current associated with a transmission burst).   Under normal circumstances, is the short locate inside the antenna?  If so, wouldn't the center conductor of the coax always be at ground potential (i.e. during reception)?  EDIT:  Thanks for the replies.  I have a big metal box sitting on my desk ready to mount the DUT (thanks for that acronym @Ali Chen ) tomorrow!
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What would be the easiest way to read data from a USB glucose meter externally with a microcontroller. Not with the software that is provided. So how could I incercept the digital signals that are being sent out?
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This might be obvious but I don't understand why RS-232 needs a stop bit. I understand that the start bit is necessary to notify the other end about the beginning of a transmission.  Let's say we are communicating at 9600BPS. We go from high to low, so that the receiver will know something is coming. The receiver also knows that we are at 9600BPS and it will receive 7 bits of data in total.  So, after receiving 7 bits, the transmission will end. Since we can determine the end of the transmission just by calculation, why do we need a stop bit as well?
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Having a bit of trouble finding the right information on google, and I'm worried I might fry some cables so I thought it best to ask some far more knowledgable than myself.  I want to connect 2 or more devices, giving them 5V/2A plus networking between them.  I figured to do so with the least amount of cables, Passive POE would be a good choice. The distance isn't far, probably maximum 20ft, as each device will be somewhere in a car, connected in to the boot/trunk area.  I'm looking at splitters and injectors, from what I've read its not as simple as just injecting 5v and it'll work? I have to worry about loss and also heat.  So my questions are, what is the best way to get 5V with max 2A current to the destinations? Do I need to send higher voltage to ensure it doesn't drop below 5, then use a regulator to ensure 5V? If I do that, the power will also be higher therefore more heat, is that ok?  Studying Wikipedia page I've read "Category 5 cable uses 24 AWG conductors, which can safely carry 360 mA at 50 V according to the latest TIA ruling"  50v * 0.36a = 18W, so if I were to send 9v * 2a = 18W. Then I could use a regulator to drop the ~9V(allowing for loss) down to 5V. Does that sound reasonable?  Many thanks
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I have to design a circuit in which I have to transfer data through lasers (serial transmission of data). Now what I was thinking was to check if the laser light is on then '1' is passed and when the laser is off '0' would be passed. Now I need to check if a 1 or a 0 was passed.   How would I check for this and another problem I'm facing is if it's on it may keep on passing 1's. How would I check for this? I though of using LDR's (Light Dependent Resistors)? Would this be okay or it there a better method?
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I'm trying to connect my desktop (running 64-bit Ubuntu 12.04) to an Airport Extreme Base Station by using an ASUS USB-N13 wireless adapter.  I plugged it in, turned on the desktop, and the adapter was immediately recognized by the system. I found my home network listed in the available networks, typed my password (with the correct encryption) and hit connect. After that, the wireless icon just flashes (propagates? emits?) indefinitely, and every couple of minutes the "Wireless Authentication Required" box pops back up.   I don't know what to do. I've seen some solutions talking about an "rt2xxx" or "rt3xxx" driver or chipset. I don't know exactly what it is, but when I typed lsmod | grep rt I got:  parport_pc rtl8192cu rtl8192c_common rtlwifi mac80211 cfg80211 parport   I'm pretty much lost. Please AskUbuntu, what do?
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As asynchronous serial communication is widely spread among electronic devices even nowadays, I believe many of us have encountered such a question from time to time. Consider an electronic device D and a computer PC connected with serial line (RS-232 or similar) and required to exchange information continuously. I.e. PC is sending a command frame each X ms, and D is replying with status report/telemetry frame each Y ms (The report can be sent as response to requests or independently - doesn't really matter here). The communication frames can contain any arbitrary binary data. Assuming the communication frames are fixed-length packets. The problem: As the protocol is continuous, the receiving side might loose the synchronization or just &quot;join&quot; in the middle of an ongoing sent frame, so it just won't know where the start of frame (SOF) is. A the data has different meaning based on its position relatively to the SOF, the received data will become corrupted, potentially forever. The required solution Reliable delimiting/synchronization scheme to detect the SOF with short recovery time (i.e. it shouldn't take more than, say 1 frame to resynchronize). The existing techniques I am aware (and using some) of: 1) Header / checksum - SOF as predefined byte value. Checksum in the end of frame.  Pros: Simple. Cons: Not reliable. Unknown recovery time.  2) Byte stuffing:  Pros: Reliable, fast recovery, can be used with any hardware Cons: Not that suitable for fixed-size frame-based communication  3) 9th bit marking - prepend each byte with additional bit, while SOF marked with 1 and the data bytes are marked with 0:  Pros: Reliable, fast recovery Cons: Requires hardware support. Not directly supported by most of PC hardware and software.  4) 8th bit marking - kind of emulation of the above, while using the 8th bit instead of 9th, which is leaving only 7bits for each data word.  Pros: Reliable, fast recovery, can be used with any hardware. Cons: Requires an encoding/decoding scheme from/to the conventional 8-bit representation to/from 7-bit representation. Somewhat wasteful.  5) Timeout based - assume the SOF as the first byte coming after some defined idle time.  Pros: No data overhead, simple. Cons: Not that reliable. Won't work well with poor timing systems like, say, Windows PC. Potential throughput overhead.  Question: What are the other possible techniques/solutions exist to address the problem? Can you point to the cons in the above list which can be easily worked around, thus removing them? How do you (or would you) design your systems protocol?
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3 years ago I went volunteering and brought back this weird USB cable and in those 3 years i never could figure out how to use this USB cable and what is the purpose of its disposition. So... what do you use this cable for (I think those are 3 USB 2.0 connectors - I don't know how to differenciate USB 2.0 and older USB's...) ?