# Forum: FPGA, VHDL & Verilog Upsampling of a received signal from UART

 Author: Roger S. (roger237) Posted on: 2014-11-27 20:42

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I have read in various literature books that the baud rate generator in
a UART module should generate a signal whose sampling frequency is
exactly 16 times the UART's designated baud rate.

For a 57600 baud rate, the sampling rate of the signal would therefore
be => 16 x 57600 => 921600 samples per second, am i right?

Given that I would then need to multiply this signal by a carrier wave
and then output it using a DAC (PMOD DA2) whose sampling rate is that of
1000000 samples per second, would I need to up-sample this signal ?

 Author: Lothar M. (lkmiller) (Moderator) Posted on: 2014-11-27 23:05

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Roger Swan wrote:
> I have read in various literature books that the baud rate generator in
> a UART module should generate a signal whose sampling frequency is
> exactly 16 times the UART's designated baud rate.
And now the question: WHY? In my RS232 code there is no specific
oversampling with a correlated rate, instead I simply wait a bit time to
read in the next bit value. Given that, I oversample a 57k6Bd signal
with e.g. 100MHz and thefore by a factor of nearly 1700...

> Given that I would then need to multiply this signal by a carrier wave
Again: Why? What is it good for to multiply a more or less randomly
chosen internal signal with a carrier?

 Author: Roger Swan (Guest) Posted on: 2014-11-28 08:43

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I am multiplying the received signal with the carrier since i need to
modulate this signal for my project purpose. The question is, given that
i am going to pass the modulated signal through a dac whose sampling
rate is that of 1Msps would i have to upsample the signal received from
uart before i do the modulation part?

Do you have any idea how i would get to know the sampling rate of the
received signal from uart?

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