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The diode in this circuit does not "achieve modulation". It's functioning as a "clamp" or "DC restoration" function so that the varying amplitude of the video does not affect the overall brighness in an objectionable way. It serves to keep the tips of the sync pulses (the most negative voltage within the composite video signal, corresponding to maximum RF ...


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The internet is different than the radio spectrum: you explicitly need a license to transmit in any radio band! With Wifi, Bluetooth and the like, you buy devices that are tested to only operate in so-called license-free bands, where an exception to that rule exist. Since you're not a radio engineer, you'd not start by trying to build a device that fits ...


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Setup and hold are influenced by the logic speed, the amount of internal skew between the clock input and the destination logic, and the skew between the signal inputs to be sampled. Faster logic will have shorter setup/hold time since it has less delay, and therefore skew. But this comes at the expense of power. Chip designers also factor in how difficult ...


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You can just chop a cable in half, carefully wire it to a breakout (keep the exposed wire straight and short as possible), and put the scope probes across either the TX or RX pair depending on which direction you want to look at. I have done this myself to debug an autonegotiation problem, which fortunately is done with lower speed data.


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An oscilloscope is the wrong tool to view ethernet data. Unless you expect signal integrity problems. Then you need the scope. The best tool for the job is a switch with port mirror and a spare network card on a PC to run pcap with Wireshark. You can also use a ethernet hub, but you can't buy those anymore. So unless you have from the 90's, you're better ...


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We can see the parity bit as a simple checksum. No checksum system, included the parity, can assure the received datum is correct. These system can however reduce the possibility of taking bad data as good, which is totally different. Let's start talking about a one byte checksum. For every datum (a packet) you receive, you have 256 possible values for the ...


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A single parity bit within an 8-bit field allows 50 % of field bit errors to be detected. Of its 256 possible values, 128 (50 %) of them have valid parity and 128 have invalid parity. Parity on your 7-bit value does not let you specifically detect errors in the actual value, only that the overall field's bit pattern is invalid.


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I'm not sure exactly what you're asking. If you fail a parity check, you are assured that there is at least one bit of the 8 in error (it may be the parity bit). There may be 3, but you have no way of distinguishing the two results. Further, if you have an even number of errors, they will result in no detected error at all. No matter what, you have no ...


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I am not at all happy with how the relay is connected. I have no idea how much the voltage on the DSR/DTR lines is. According to the RS232 standard they can be between +/-3 to +/-25 Volts. That is a huge range Using them to switch a relay on and off is unlikely to work because: a. The signal is unlikely to have enough energy (current) to activate a relay. ...


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The DB9 breakout board that you specified is also a level-shifter. Supply it with 3.3V from the RPi. Then you can connect it directly to the RPi GPIO pins, no resistor is necessary. The hardest part is getting the signal direction correct (3.3V and RS-232). TX & RX are only meaningful when the point of view is known. The RS-232 DB9 cable may need to be ...


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Since modern PCs rarely have COM ports built into them anyway, it is best to use a USB to serial converter that uses 3.3V signal levels. I use one from FTDI. https://www.amazon.com/Converter-Terminated-Galileo-BeagleBone-Minnowboard/dp/B06ZYPLFNB/ Or search for: USB to TTL Serial 3.3V


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