20

For cold or dry solders on BGAs, you are working blind without X-ray or just functional testing like yours, so it's not easy for sure. First order of business would be to reflow the BGA with hot air. There are plenty of YouTube videos of GPUs being fixed this way in your home oven with some care. If this does not help and it's your one-off board and not ...


16

You need to use a transceiver when you want to bring out high speed signals from inside the FPGA and interface with the real world. Typical examples are to communicate with other high speed parts on the same board (for example another FPGA or ADC) or to interface off board (for example using PCI, HDMI or ethernet). In order to send these high speed ...


9

The rule of thumb a lot of people use is that lower frequencies will have better "penetration" than higher frequencies. That's true in some cases, but not all. This is probably derived from calculating skin depth of materials. The skin depth is just how deeply into a material an electromagnetic wave of a particular frequency can penetrate. The equation used ...


7

Basically what's done is some 8-bit message words have two corresponding 10-bit code words. One of these has positive disparity (more 1's than 0's) and the other has negative disparity (more 0's than 1's). When encoding you keep track of the running disparity. If the running disparity is positive and the next input octet gives you a choice of code words, ...


7

Unfortunately, BGA is not easy to rework. You could try reflowing again, or if you happen to have a via by the pin, shove a bit of flux there and heat with a hot air gun. If that doesn't work you have 1 of 2 options. You can either scrap the board and use a new one, or you can remove the IC, clean all of the pads, then you will have to re-ball the IC. This ...


6

In principle you should be able to multiplex MCU CAN signal lines, prior to their being used to interface to a CAN physical layer transceiver, using something like a 74HC4052. In practice, I'd suggest that it's not a very good idea to do so. The problem is that multiplexing would mean that you are guaranteed to periodically miss transmissions from each of ...


6

Did you estimate the proportion of time your system will actually be transmitting data? In most applications, this is very small, proabably less than 1%. Most of the time, transceivers are just idle. That is why it isn't really specified, because it doesn't account for much in the total power consumption. Also note that I saw it is actually specified for ...


6

Would it be possible to take a standard SFP transceiver module and use that across free space rather than through a fibre? In other words, to point two transceivers at each other from a distance without any fiber optic cable between them. No. "Proof" to follow: The point of the fiber is to get almost all energy from the transmitter into the receiver. You'd ...


6

Here is the outline of a link analysis: we'll assume you want a low bit-error-rate (BER), maybe 1 in a Billion; for normal OOK on-off-keying transmission, and similar for BPSK, etc, you'll need a signal-noise-ratio SNR of about 20dB with the noise measured in the data-bandwidth (or for some maths, in data-BW/2). Let's compute the room-temperature noise ...


5

A standard piezoelectric ultrasonic transducer will not work efficiently at sub harmonics or harmonics - it's a 2nd order resonant mechanical device with high Q - there aren't different modes of operation as you might find with some crystals (for instance).


5

You don't tell us anything in your profile about your level of experience or education, so I'll give a very generic answer. The best tool to start with would be a spectrum analyzer, which can tell you what frequency the system operates on, and also allows you to learn something about the overall patterns of activity, and can offer clues about the modulation ...


5

There are (in this context) two types of USB Micro-B connector; I tend to think of them as "long edge close to the PCB" and "long edge away from the PCB". You're using the "long edge close to the PCB" kind. Use the other kind and the order of the pins flips. Unfortunately there doesn't seem to be a search term (for Digikey or Element14, at least) that can ...


5

You do not say where you are. The radio you reference requires you to hold an Amateur Radio operator's license. If you are in the United States, you need an Extra Class license (the highest), because the operating frequency is in the Extra Class sub-band of the 40 meter ham band. If you are somewhere else, check the local laws. (If you are in Thailand, ...


5

Those buffer the protected pin from the ESD event while ESD diodes do their job since it takes a finite amount of time for them to do so. It is similar to placing the ESD diodes as close to the connector as possible and as far away from protected pin as possible which uses the parasitic inductance of the traces instead of a resistor. Ferrite beads can also ...


4

Yes, they are compatible. The functionality is determined by the chip, not by the surrounding components. With some care the NRF24L01 is also compatible with the NRF24L01+, RF70, and RF73. "It tells that it supports 1 to 6 communication? " - is that a question? - Yes, they all support 1:N communication (in datagram mode - no acknowledging/retransmission). ...


4

I am answering this based on one particular SFP module's datasheet. I believe that everything I'll say applies in general, but I haven't checked it against the standard itself. I did find a copy of the standard online, but I'm not sure whether this version is current. TX_FAULT: "This signal is an open collector output (pull-up required on the host board). A ...


4

8b/10b encoding has a wikipedia page with good explanations and also the encoding tables : http://en.wikipedia.org/wiki/8b/10b_encoding I think you can also look at some bus standards that use 8b/10b to have more practical examples.


4

It seems your circuit is incomplete or got pins mixed up. It is extremely unlikely that outputs of the 74ls14 are used with the input being open. Using a schmitt-trigger circuit when receiving clock/enable like signals to improve noise immunity is quite sensible. As the 74ls14 is inverting, connecting two inverters in series to remove inversion is sensible ...


4

That's what happens when you rely on undocumented behavior. Unless I'm misinterpreting your question, you seem to expect to be able to override the xxx213 logic outputs while they are enabled ... Why do you expect to be able to do this? The behavior you're seeing indicates that the SP213's logic outputs are better able to source current to drive a high level ...


4

Assuming the receiver side of a transceiver is boring to you (just a comparator with some hysteresis): TI's DS9638 (datasheet of the SNLS389D) actually has an equivalent circuit for a single transmitter circuit: To illustrate what's happening a bit better: In green, the identical output stages. Look at the left: Q15 has the job of pulling the output low ...


4

You start by looking up the datasheet for the nRF24L01. In it, you will find all the information about what it takes to use that chip. You will also find this circuit diagram: Right under the schematic is a parts list: That should answer your question about what you need. And, yes, you must include an antenna. Virtually every project that involves an ...


4

It is not entirely clear what you are asking here, or what you say happens. Sometimes things outside the limits of the data sheet will work - or at least seem to for a while. The output voltage of your 74LS173 is so low because you are heavily loading it with the LEDs, and because LS logic doesn't have all that strong output drive to begin with. The best ...


4

LORA WILL do what you want in many cases - and MUCH more if you try hard enough. 766 km from a balloon. LORA with proper configuration is about the longest range system per link budget that you can get. The balloon range record was 714 km (!!!) in July 2019 - see Here. That's beyond some theoretical calculations but your 100 km is well inside theoretical. ...


3

Try CoilCraft - they have this that is suitable for your operating frequency: - I don't think they can handle much power (1/4 watt say CoilCraft). Insertion loss is 0.7dB which is OK but nothing special. I still believe an air-cored transformer is the best bet.


3

Talking specifically about USB, the terms "transceiver" and "PHY" are synonyms and are used interchangeably. In all cases, some aspects of the physical layer are implemented by the controller, not the PHY. This is the case for all PHYs: the full-speed ones with a serial USB interface, the high-speed ones with ULPI or UTMI, and super speed (USB 3_ with PIPE ...


3

I would suggest you edit this question and use the code format to pretty print your code as it's very hard to follow the way it currently is. The value for the pipe variable is an address, more or less the equivalent of your computer IP address: when a message is broadcast into the air all the potential receivers will filter out any message not ...


3

The 74HCT245's obvious purpose is to achieve bidirectional transfer of bytes between two buses, but the TTL chip it is based on was designed to do more than that. The 74LS245 had high current outputs that could sink 25mA, and its inputs had hysteresis to clean up noisy bus signals. It was often used for connecting weak devices to a heavily loaded bus. ...


3

No, typical buffers can't detect a high-Z input and put their own outputs in high-Z in response. If there is a buffer that can do that, I am unaware of its existence. If you want your buffer to have high-Z outputs, a separate EN (often active-low) input pin is usually used. If a buffer is enabled for output and has a high-Z input, there is a high risk ...


3

No. One reason is getting the whip antenna for the bluetooth to accept such a "low frequency" signal requires hardware modification and re-tuning of the reception circuitry, since BT is 2.4GHz. Another reason, even if you'd get the chip to accept the lower centre band frequency is that the encoding scheme and signalling bands on both protocols are vastly ...


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