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I´m trying to set the baud rate of my serial port using stty -F /dev/ttyS0 9600 the problem is that i check on the oscilloscope I get a 8 times faster baud rate so I need to configure 1200 to get 9600 and this applies for all other typical speeds. Does anyone knows the reason of this if there is a way to adjust the clock speed, PLL or any clock multiplier or divisor on the system?

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  • Baud rates are not the same as clock speed (baud is also not the same as bits per second, either!). Look up the terms and how they apply to serial communications. Then, if you still have issues/concerns, edit your question appropriately so you are NOT comparing incompatible terms.
    – C. M.
    May 10, 2021 at 19:59
  • thanks you give me the correct answer, I'm setting the serial port speed to 9600 and this is the baudrate and i was measuring the bit time with the oscilloscope, and I was confused because early modems used to transmit only 1 bit per baud but it is because it is "packing" 8 bits into each baud May 11, 2021 at 22:06
  • That is not entirely correct, either. Baud is the rate it transmits one complete unit of data--which can be 8-bits, or even 7-, 9- or 10-bits, depending on era and if it includes a parity bit, checksum bit, and so on.
    – C. M.
    May 12, 2021 at 0:36
  • To clarify my last: "one complete unit" can be interpreted different ways. I mean it in the sense of at the hardware level--one complete frame which is often the payload plus any overhead. Here is a more complete and accurate explanation: What is the difference between baud rate and bit rate?
    – C. M.
    May 12, 2021 at 0:49

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I was setting the serial port speed to 9600 and this is the baud rate and I was measuring the bit time with the oscilloscope, the problem was that I was expecting the baudrat = bps because early modems used to transmit only 1 bit per baud but it is because it is "packing" 8 bits into each baud that is the reason why the measurement it was always 8 time the speed.

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